Class 12 – Page 4 – BSE Odisha

CHSE Odisha Class 12 Biology Solutions Chapter 16 Biodiversity and its Conservation

August 1, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 16 Biodiversity and its Conservation Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 16 Question Answer Biodiversity and its Conservation

Biodiversity and its Conservation Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
Genetic diversity refers to
(a) variation in the genetic material
(b) variation in the populations
(c) variation in the number of species
(d) variation in the animal distribution
Answer:
(a) variation in the genetic material

Question 2.
Species diversity means
(a) number of species
(b) relative abundance of species
(c) pecies composition
(d) genetic diversities
Answer:
(b) relative abundance of species

Question 3.
The Forest Conservation Act was enacted in
(a) 1972
(b) 1952
(c) 1980
(d) 1991
Answer:
(c) 1980

Question 4.
Conservation of wild animals and plants in sanctuaries and national parks is
(a) ex situ conservation
(b) in vivo conservation
(c) in vitro conservation
(d) in situ conservation
Answer:
(d) in situ conservation

Question 5.
Corbett national park is situated in
(a) Uttarakhand
(b) Jharkhand
(c) Uttar Pradesh
(d) Himachal Pradesh
Answer:
(a) Uttarakhand

Question 6.
Following mass extinctions, recovery to the same level of biodiversity has taken
(a) hundreds of years
(b) millions of years
(c) thousand of years
(d) billions of years
Answer:
(b) millions of years

Express in one or two words

Question 1.
A species originated in one place and found no where else.
Answer:
Endemic species

Question 2.
Organism whose no living representative is seen.
Answer:
Extinct

Question 3.
Biogeographic region with high endemism and habitat destruction.
Answer:
Biodiversity hotspot.

Question 4.
Conservation of biodiversity in its natural site.
Answer:
In situ conservation.

Question 5.
Diversity of all life forms in the earth.
Answer:
Biodiversity.

Correct the statement by changing the underlined word(s)

Question 1.
Hybrid plants of a species are the source of disease resistant genes.
Answer:
Disease resistant

Question 2.
Bhitarkanika is a hotspot.
Answer:
national park of India.

Question 3.
Hotspots are characterised by low endemism and habitat destruction.
Answer:
high

Question 4.
Botanical gardens are meant for in situ conservation of biodiversity.
Answer:
ex situ

Question 5.
WWF has enlisted endangered species in Red Data Book.
Answer:
IUCN

Fill in the blanks

Question 1.
The term ‘biodiversity’ was coined by ……….. .
Answer:
Thomas E. Lovejoy

Question 2.
The three levels of biodiversity are ………… diversity, species diversity and ……….. diversity.
Answer:
genetic, ecological

Question 3.
There are ……….. numbers of megabiodiversity countries in the world.
Answer:
17

Question 4.
India had ………….. numbers of biodiversity hotspots.
Answer:
three

Question 5.
The Wildlife Protection Act was enacted in …………… .
Answer:
1972

Question 6.
The UN conference of human environment was held in ……………. in 1972.
Answer:
Stockholm

Question 7.
The expanded form of IUCN is …………….. .
Answer:
International Union of Conservation of Nature and Natural Resources.

Question 8.
The first national park of India is …………. national park.
Answer:
Hailey (Jim Corbett)

Question 9.
Odisha has ……….. numbers of national park.
Answer:
two

Question 10.
There are ………… numbers of wildlife sanctuaries in Odisha.
Answer:
19

Question 11.
India has …………. numbers of biosphere reserves.
Answer:
18

Question 12.
The concept of biosphere reserve made a beginning under ……….. programme instituted by a UN body, namely ……….. .
Answer:
Man and Biosphere (MAB), UNESCO

Short Answer Type Questions

Write short note on each of the following

Question 1.
Ecological diversity
Answer:
Ecological Diversity (Diversity among Communities):
It explains about the variety of ecosystems present in the biosphere. The community composition, i.e., assemblage of several interacting populations in a given space at a particular time is affected directly by the environment. Thus, it is the diversity at the level of communities and ecosystems of a region.

Question 2.
Wildlife Protection Act (1972).
Answer:
Wildlife Protection Act (1972) It was enacted to provide protection to wild flora and fauna and other natural resources. This act offers protection based on two approaches that are
(a) Species based approach for specific endangered species which are protected by special projects such as Project Tiger.
(b) Habitat based approach which is conservation of endangered wild flora and fauna in National Parks and Wildlife Sanctuaries.

Question 3.
In situ conservation.
Answer:
It involves the to protection of plants, animals and microorganisms within their natural ecosystems. The i in situ conservation is the most effective way of protecting the species and improving the quality of the habitat they live in. The in situ approach is preferable because of the fact that not much diversity can be conserved outside the centres of diversity.

Biodiversity at all its levels can be conserved in situ by comprehensive system of protected areas such as the national parks, wildlife sanctuaries, natural reserves, natural monuments, cultural landscapes, biosphere reserves, wetlands, etc. So far, in situ practice is considered most effective method of protecting and propagating the species and improving the quality of their habitats.

Question 4.
Ex situ conservation
Answer:
Ex situ (Off-site) Conservation:
It refers to conservation of biological diversity outside the boundaries of their natural habitats by perpetuating sample population in genetic resource centres, e.g. zoos, botanical gardens, culture collections, etc., or in the form of gene pools and gametes storage for fish, germplasm banks for seeds, pollen, semen, ova, cell, etc. Zoos also help in captive breeding of organisms which are endangered, whereas botanical gardens have seed gene banks, tissue culture labs and other technologies for storing and growing germplasm.

Question 5.
Biosphere reserve
Answer:
These are large tracts of protected land used for preserving the genetic diversity of an ecosystem by preserving wildlife. The creation of biosphere reserves was initiated in 1975 under the Man and Biosphere (MAB) programme of UNESCO. It is category V protected area designated by IUCN.

Each biosphere reserve integrates human activities and has following zonation

Core zone Strictly protected.
Buffer zone Sustainable and recreation activities allowed.
Transition zone Anthropogenic activities like research and sustainable development allowed.
Zone of human encroachment Normal anthropogenic activities allowed.

Differentiate between the following

Question 1.
In situ and Ex situ conservations.
Answer:
Differences between in situ conservation and ex situ conservation are as follows

In situ conservation	Ex situ conservation
It is the conservation of species in their natural habitats.	It is the conservation of species outside their natural habitats.
The endangered species are protected from predators.	The endangered species are protected from all adverse factors.
Augmentation of depleted resources is done.	Animals or plants are kept under human supervision and provided with all the essential necessities for survival.
e.g. national parks, sanctuaries and biosphere reserves.	e.g. zoos, botanical gardens, cultural collections, etc.

Question 2.
Genetic diversity and Species diversity.
Answer:
Differences between genetic diversity and species diversity are as follows

Genetic diversity	Species diversity
It is related to the number and type of genes and their alleles found in organisms.	It is related to the number, type and distribution of species found in given area.
It is the trait of the species.	It is the trait of the community.
It influences adaptability and distribution of a species in diverse habitat.	it influences biotic interaction and stability of the community.

Question 3.
National park and Sanctuary.
Answer:
Differences between national park and sanctuary are as follows

National park	Sanctuary
It is meant for protection of flora and fauna of the area.	It is meant for protection of one or more group of wild animals.
Cultivation of land, grazing and forestry are not allowed.	Cultivation of land, grazing and forestry are allowed.
Private ownership is not permitted.	Private ownership is permitted.
Boundary is well demarcated.	Boundary is not well demarcated.
e.g. Corbett National Park (Uttarakhand)	e.g. Bird Sanctuary Chilika (Odisha).

Question 4.
Extinct species and Endangered species
Answer:
Differences between extinct species and endangered species is as follows

Extinct species	Endangered species
A taxon is extinct when there is no reasonable doubt that the last individual has died, e.g. Indian cheetah.	A species is endangered when it is facing a very high risk of extinction in the wild in the near future, e.g. giant panda, polar bear.

Long Answer Type Questions

Question 1.
What is meant by biodiversity? Write the causes of loss of biodiversity.
Answer:
The term ‘biodiversity’ was first used by Thomas E. Lovejoy (1980) to refer the number of species of a region. It is the degree of variation of life occurring at different levels like genetic, organismal and ecological. These levels forms a hierarchy of biodiversity

Loss of Biodiversity:
The loss of biodiversity is a global crisis. Extinction of species is a natural phenomenon aided by the physical changes in the environment. However, the accelerated rates of species extinctions, that the world is facing now are largely due to human activities.
Till now, five episodes of mass extinction of species have occured in the history of biological evolution. The sixth episode of extinction of species however, is credited to human activities, which otherwise would not have occurred.

According to IUCN estimates, 12259 species have become extinct since the time of origin of life on the earth. The major cause of the biodiversity losses are called drivers, which belong to two classes namely, direct and indirect.

Direct Drivers Factors
The directly influence the ecosystem processes which bring about the mass extinction of species.
The various processes associated with direct drivers includes

1. Habitat destruction and fragmentation Conversion of forest land for agriculture, development projects, mining operation, etc., leads to the destruction of the natural habitats of the organisms.
Indiscriminate agricultural practices involving use of chemical fertilisers and pesticides are potent factors for the destruction of habitats. When a large population fragments into smaller ones there is more inbreeding and inbreeding pressure leading to population decline.

2. Overexploitation of natural resources Humans are dependent on nature for food and shelter, but when ‘need’ turns to ‘greed’, it leads to overexploitation.

To meet the need for increased housing, the natural habitats of animals and plants are being destroyed. This results in habitat loss and extinction of species. It has caused extinction of many species in last 500 years. In addition, indiscriminate hunting of wild animals has made their status in Red book as endangered or critically endangered.

3. Introduction of alien invasive species When alien species are intentionally or unintentionally introduced in a particular area, they might turn invasive and cause decline or extinction of endogenous species, e.g., Eichhornia is known as the ‘Terror of Bengal’. It was introduced as ornamental plants but it became wild in India because of invasiveness.
Similarly, Lantana and Parthenium were important due to their ornamental and food values, respectively but, they become wide spread due to favourable environmental conditions.

4. Climate change The global climate is changing, due to the anthropogenic activities like greenhouse gases and it has led to global warming. This is causing melting of glaciers, polar ice caps, etc. This may submerge low lying coastal habitats and also plants and animals are unable to adapt themselves to this change which is causing their elimination.

5. Environmental pollution It is another major factor for species extinction. Pollution may reduce and eliminate populations of sensitive species. Environmental pollution is most commonly caused by accumulation of non-biodegradeble wastes like plastics. Agricultural chemicals like pesticides enters the food chain and get deposited in the body of higher organisms. This effects the population of fish eating birds and falcons by disturbing their reproductive process.

Question 2.
How can the biodiversity be conserved? Add a note on importance of biodiversity.
Answer:
Biodiversity is directly or indirectly involved in maintaining the well-being of human society. Thus, scientists have classified the values of diversity as ecosystem goods, i.e., natural products harvested from ecosystems and directly used by humans and ecosystem services, involving different ecosystem processes which indirectly benefit human life.

Biodiversity Conservation:

The protection, uplift and scientific management of biodiversity at its optimum level for present and future generations is known as biodiversity conservation.
The International Union for Conservation of Nature and Natural Resources (IUCN) or World Conservation Union, World Wide Fund for Nature (WWF), Food and Agricultural Organisation (FAO) and United Nations Educational Scientific and Cultural_Organisation (UNESCO) formed the world conservation strategy in 1980 for the conservation and sustainable use of biological resources. For this, two major types of conservation strategies were framed. These are

1. In situ (On-site) Conservation:
It involves the to protection of plants, animals and microorganisms within their natural ecosystems. The i in situ conservation is the most effective way of protecting the species and improving the quality of the habitat they live in. The in situ approach is preferable because of the fact that not much diversity can be conserved outside the centres of diversity.

2. Ex situ (Off-site) Conservation:
It refers to conservation of biological diversity outside the boundaries of their natural habitats by perpetuating sample population in genetic resource centres, e.g. zoos, botanical gardens, culture collections, etc., or in the form of gene pools and gametes storage for fish, germplasm banks for seeds, pollen, semen, ova, cell, etc. Zoos also help in captive breeding of organisms which are endangered, whereas botanical gardens have seed gene banks, tissue culture labs and other technologies for storing and growing germplasm.

Biodiversity Preservation Methods and Sites

A protected area, as defined by IUCN, is an area (either land or sea) especially dedicated for the protection and maintenance of biological diversity through legal and ‘ other effective ways. IUCN has classified protected area into six different types. Some of these protected areas are, discussed below

National Parks:
India’s first National Park (IUCN category-II protected area) was Hailey National Park, now known as Jim Corbett National Park, established in 1935. According to National Wildlife Database, there were 103 National parks in India as in April, 2015. A national park is an area maintained by government and dedicated to conserve the environment, natural and historical objects and the wildlife therein. Operations such as plantation, cultivation, grazing forestry are not allowed in national parks. Private ownership rights and habitat manipulation are also prohibited. IUCN (1975) has adopted following keypoints to define a national park.

A national park is a relatively large area reserved for the betterment of the wildlife. The habitats of native plant and animals becomes the site of scientific, educational and recreative interests along with maintenance of its aesthetic values.
Since, human intervention is nil or limited, the operating ecosystem remains unaltered and conserved.
It is also defined as an area where the highest authority take measures to prevent exploitation and enforce conservation measures.
A place where visitors are permitted to enter only in special conditions like inspirational, cultural and recreative purposes.

Hotspots of Biodiversity:
The concept of hotspot was given by Norman Myers in 1988. Hotspots are areas that are extremely rich in species diversity, have high endemism and are under constant threat. There are 34 hotspots which cover less than 2% of earth land area of the world. In these sites nearly 75% population of world’s most threatened mammals, birds and amphibians, approximately 50% plants and 42% land vertebrates are conserved (Conservation International, 2003).

According to Myers, the key criteria for an area to be assigned as biodiversity hotspot are

It must contain atleast 0.5% or 1,500 of the world’s 3,00,000 species of vascular plants as endemics.
It should have lost atleast 70% of its primary vegetation.

Tropical forests appear in 15 hotspots, Mediterranean – type zones in 5, 9 hotspots are mainly or completely made up of islands and 16 hotspots are in the tropics. About 20 % of the human population lives in the hotspot regions.

Tropical Andes hotspot has 20,000 endemic plants and 1567 vertebrates and it is at the top of the list. Four regions of India that fulfills the criteria of hotspots are The Western Ghats and Sri Lanka, The Eastern Himalayas, Indo-Burma (North-Eastern India South of Brahmaputra river)and Sundarland (Nicobar Islands). These sites are also known as Gade of speciation.

The Western Ghats are a chain of hills that lies parallel to the Western coast of peninsular India. These regions have moist deciduous forest and rain forest and have high species diversity and high levels of endemism. Nearly 77% of the amphibians and 62% of the reptile species found here are found nowhere else. Over 6000 vascular plants of over 2500 genera are found in this hotspot, of which over 3000 are endemic.

Much of the world’s species like black pepper and cardamom have their origins in the Western Ghats. It also harbors over 450 bird species, about 140 mammalian species, 260 reptiles and 175 amphibians. Over 60% of the reptiles and amphibians are completely endemic to this hotspot.

The Eastern Himalayan hotspot has approximately 163 globally threatened species including the one-horned rhinoceros, the Wild Asian Water buffalo and in all 45 mammals, 50 birds, 17 reptiles, 12 amphibians, 3 invertebrate and 36 plant species.
Thus, hotspots are the most precious sites for biodiversity conservation and should be protected from exploitation.

Wildlife Sanctuary:
It is IUCN category IV of protected area. A wildlife sanctuary can be established by a gazette notification from the State Forest Department, where protection is provided to vulnerable, endangered and critically endangered wild animals life. Operations such as procuring timber and minor forest products and private ownership are allowed provided they do not cause any adverse effects on the animals. Till 2015, there were 520 wildlife sanctuaries in India, covering 122867.34 km2 (3.74%) of land in India. The state of Odisha has 19 wildlife sanctuaries, which are listed below
CHSE Odisha Class 12 Biology Solutions Chapter 16 Biodiversity and its Conservation 2

Biosphere Reserve:
These are large tracts of protected land used for preserving the genetic diversity of an ecosystem by preserving wildlife. The creation of biosphere reserves was initiated in 1975 under the Man and Biosphere (MAB) programme of UNESCO. It is category V protected area designated by IUCN. Today, India has 18 biosphere reserves, some of which are also included under National Parks and Odisha has a share of one in Simlipal.

Each biosphere reserve integrates human activities and has following zonation

Core zone Strictly protected.
Buffer zone Sustainable and recreation activities allowed.
Transition zone Anthropogenic activities like research and sustainable development allowed.
Zone of human encroachment Normal anthropogenic activities allowed.

Out of 18 biosphere reserves, 8 of them are a part of world network of Biosphere Reserves based on MAB Programme of UNESCO.

The objectives of this programme are

Conserving representative samples of ecosystems.
In situ conservation of genetic diversity.
Facilitating basic and applied research in ecology and environmental biology on site.
Create opportunities for environmental education k and training.
Promoting and creating awareness about sustainable management of living resources.
Promoting international cooperation.

Therefore, the biosphere reserves have three junctions, that includes

Conservation of ecosystems and genetic variations.
Promotion of sustainable economic and human development.
They serve as examples of education and training local, regional, national and international issues of sustainable development.

A protected area to be declared as a biosphere reserve should have the following essential features

Abundant genetic diversity should be present.
It should be unique in itself.
The area should be legally protected for long term.
Appropriate size for effective maintenance of natural populations so that there is no genetic drift.
Sufficient natural resource available for ecological research, education and training. It should be a natural home for the endangered species of plants and animals.

Question 3.
Give an account of biodiversity and its conservation measures.
Or
Give an account of the concept of biodiversity.
Answer:
The term ‘biodiversity’ was first used by Thomas E. Lovejoy (1980) to refer the number of species of a region. It is the degree of variation of life occurring at different levels like genetic, organismal and ecological. These levels forms a hierarchy of biodiversity. The integration of several sciences such as ecology and genetics to sustain biological diversity at all its levels is called conservation biology.

Levels of Biodiversity

In 1986, Norse and Me Manus explained the three levels of biodiversity. These include

1 Genetic Diversity:
It involves variations in genetic composition among the individuals of a species. This variations could be in the nucleotides, genes, entire genome or chromosomes. This type of diversity arises due to genetic recombination during sexual reproduction and mutation.

Variations in the genes of a species increases with the increase in size and environmental parameters of the habitat. Genetic diversity is useful as it helps an individual to adapt to changing environmental condition, natural selection and is essential for healthy breeding. It also helps in speciation or evolution of new species.

2. Organismal or Species Diversity (Diversity among Species):
It is the variety in the number and richness of a species of a region. Sometimes, a species remains confined to a particular area and is found only in that area. Such species are said to be endemic, e.g., Indian giant squirrel is endemic to Panchmarhi hills in Madhya Pradesh.

The IUCN (International Union for Conservation of Nature and Natural Resources) recognises three types of species diversity, i.e.

Alpha (α) diversity It refers to the variety of species within a community. It is also referred to as species richness, i.e., the number of species per unit area.
Beta (β) diversity It refers to the diversity of species among communities.
Gamma (γ) diversity It refers to the diversity of species across a wide geographical range.

The important features of species diversity to the ecosystem are as follows

Increased biodiversity provides resistance to the ecosystem against natural disasters.
Ecosystem with more species shows more yields and greater productivity with variation of biomass.
Community with more species generally tends to be more stable than those with less species.

3. Ecological Diversity (Diversity among Communities):
It explains about the variety of ecosystems present in the biosphere. The community composition, i.e., assemblage of several interacting populations in a given space at a particular time is affected directly by the environment. Thus, it is the diversity at the level of communities and ecosystems of a region.

Patterns of Biodiversity

Biodiversity is not uniform throughout the world. It varies with the changes in latitude and altitude. For many groups of animals and plants, there are specific patterns in diversity based on the favourable environmental conditions.
The pattern of biodiversity among different regions is discussed below

Latitudinal Gradients:
Species diversity decreases as we move away from the equator towards the poles. It means biodiversity is more at lower latitude (equator) than the higher latitude (poles). The biodiversity gradient is steep in Northern hemisphere than the Southern hemisphere.

Biodiversity in Tropics
Tropics (latitudinal range of 23.5°N to 23.5°S) harbour more species than temperate or polar areas, e.g., Colombia located near the equator, has 1,400 species of birds.

New York located at 41°N has 105 species of birds, while Greenland at 71°N has only 56 species of birds. India, with most of its area in tropical latitude has more than 1200 species of birds. A forest of equal area in tropical region (like equator) has 10 times more species of vascular plants than in temperate region (like Mid-West of USA). Amazonian rainforest in South America has the greatest biodiversity on the earth with more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals and amphibians, 378 of reptiles and more than 1,25000 of invertebrates.

Reasons for Greater Biodiversity in Tropics
The factors making tropical rainforests rich in biodiversity are

Tropical latitudes have remained undisturbed for million of years allowing speciation.
Tropical environments are relatively constant throught the year which promotes niche specialisation and greater diversity.
High productivity leads to greater diversity. It is also found that species diversity increases with area (species area curves), how it peaks in areas with intermediate productivity or intermediate rates of disturbance. The more variable the habitat, the greater the species diversity within it. This pattern was offered as one of the reasons why there are more species in bigger area as more area covers a greater variety of habitat.

Importance of Biodiversity

Biodiversity is directly or indirectly involved in maintaining the well-being of human society. Thus, scientists have classified the values of diversity as ecosystem goods, i.e., natural products harvested from ecosystems and directly used by humans and ecosystem services, involving different ecosystem processes which indirectly benefit human life.

Direct Value

Food It includes all the plant and animal products used as food by humans, e.g., cereals, pulses, vegetables, fruits, milk, beverages, etc.
Clothing It includes natural fabric made out of cotton, jute and natural silk (harvested from silk moth).
Shelter It includes raw material obtained from ecosystem for making houses, e.g., wood, etc.
Medicines Large number of substances with therapeutic properties are obtained from variety of plant species and animals, e.g.
1. Quinine Antimalarial drug, obtained from the bark of Cinchona plant.
2. Anticoagulants Antihemorrhagic drugs, extracted from blood sucking animals.
3. Snake venom and toxins Drugs for neural and muscular disorders.
4. Penicillin, tetracyclins and streptomycins Antibiotics extracted from microorganisms.
5. Biocidal compounds Used in manufacturing antibiotics, extracted from beetles, millipedes, snails and ants.
Industrial products A variety of industrial products are directly made out of biological resources, e.g. timber, fuel, dyes, oil, etc., from plants and leather, etc., from animals skin.

Indirect Value:

1. Biological control It is the use of microorganisms for the manufacture of antibiotics, oral contraceptives, etc., and management of pests, increasing soil fertility, cleaning oil spill (super bug), treatment of sewage and solid waste, recovery of metals (bioleaching), monitoring pollution generating biofuel, etc.

2. Environmental modulation. It includes some animals and plants which influence and modulate the environment directly and indirectly. Such animals and plants are known as ecosystem engineers. One of these are keystone species whose extinction reduces abundance of other species in the community.

A well known example of ecosystem engineer is beaver (a mammal). It influence plant and animal communities and the entire biodiversity of watershed area by
(a) Creating dams using logs in river channels
(b) Modifying nutrient cycling
(c) Influencing decomposition dynamics.

3. Ecosystem functions and services Biodiversity plays a major role in many ecosystem services and functions such as replenishing oxygen through photosynthesis, pollination through bees, regulation of global climate, retention of rainwater in aquifers and reservoir, control of floods, etc.
Nature always key a check on these activities to maintain a state of equilibrium (homeostasis), which further helps in the sustainable development of resources. However, overexploitation of biolgical resources by humans leads to destabilisation of ecosystem balance.
For example,

Decreased flora of an area leads to CO₂ increase in the atmosphere which causes temperature elevation of that area.
Increased carnivore population decreases the herbivore population by predation which then increase the vegetation.
Declined population of microflora prevents the recycling between complex organic matter and simple inorganic matter.

4. Ecotourism The diverse biological resource of a country motivates people from around the world to undertake recreational activities like tours to enjoy the diverse wildlife and charismatic landscape. In return the host country earns a large sum of foreign exchange as revenue.

Loss of Biodiversity

The loss of biodiversity is a global crisis. Extinction of species is a natural phenomenon aided by the physical changes in the environment. However, the accelerated rates of species extinctions, that the world is facing now are largely due to human activities.

Till now, five episodes of mass extinction of species have occured in the history of biological evolution. The sixth episode of extinction of species however, is credited to human activities, which otherwise would not have occurred.

Direct Drivers Factors

The directly influence the ecosystem processes which bring about the mass extinction of species.
The various processes associated with direct drivers includes

1. Habitat destruction and fragmentation Conversion of forest land for agriculture, development projects, mining operation, etc., leads to the destruction of the natural habitats of the organisms.
Indiscriminate agricultural practices involving use of chemical fertilisers and pesticides are potent factors
for the destruction of habitats. When a large population fragments into smaller ones there is more inbreeding and inbreeding pressure leading to population decline.

2. Overexploitation of natural resources Humans are dependent on nature for food and shelter, but when ‘need’ turns to ‘greed’, it leads to overexploitation.
To meet the need for increased housing, the natural habitats of animals and plants are being destroyed. This results in habitat loss and extinction of species. It has caused extinction of many species in last 500 years. In addition, indiscriminate hunting of wild animals has made their status in Red book as endangered or critically endangered.

Similarly, Lantana and Parthenium were important due to their ornamental and food values, respectively but, they become wide spread due to favourable environmental conditions.

Indirect Drivers
These influences or changes one or more the direct driver. They include

Population growth Rapid increase in human population causes loss of biodiversity becatise population explosion results in rapid growth of exploitation of natural resources such as water, food and minerals. If this trend of population growth continue, the resources will be depleted faster and most species will face the risk of extinction.
Income and lifestyle Today people’s income has increased tremendously which has led to more luxurious lifestyle of people. For leading this, they tend to use more and more of natural resources which causes pollution, degradation of environment and biodiversity loss.

Extinction of Species

In the history of earth many species have disappeared and new ones got evolved over million of years. The major threat to biodiversity is extinction of species Extinction is the total elimination or dying out of species (fossilisation) form the earth. As, we already know, the extinction of species is a natural process which accelerates due to human activities.

There are generally three types of extinction
1. Natural extinction It is a slow process of replacement of existing species with the better adapted species due to alternate evolution, changes in environmental condition, predation and diseases. Extinction of species occurs due to combination of genetic and demographic factors.

2. Mass extinction It occur due to catastrophes, which struck the earth several times. A mass extinction occurred about 225 million years ago in Permian period when 90% of shallow marine invertebrates disappeared.
Another mass extinction occurred between cretaceous and tertiary period over 60 million years ago when dinosaurs and a number of other organisms disappeared.

3. Anthropogenic extinction These are extinction of organisms due to human activities like hunting, overexploitation and habitat destruction, e.g. dodo (Raphus cucullatus), Tasmanian wolf, etc. Anthropogenic extinction is causing a sixth extinction of species. It is 100-1000 times more faster than the rate of natural extinctions.

IUCN and Red List
IUCN is International Union of Conservation of Nature and Natural Resources which is now called World Conservation Union (WCU). It has its headquarters at Morges, Switzerland. IUCN maintains a Red Data Book (RDB) or Red List which is a catalogue of taxa facing risk of extinction. Red Data Book was initiated in 1963.
The purpose of red list is to

(i) Provide awareness to the degree of threat to biodiversity.
(ii) Provide global index about already declined of biodiversity.
(iii) Identification and documentation of species at high risk of extinction.
(iv) Preparing conservation priorities and help in conservation plan.
(v) Information about international agreements like conservation on biological diversity and CITES (Convention on International Trade in Endangered Species) of Wild Fauna and Flora.

The IUCN Red List 2004 has recorded a total loss of 784 species in the last 500 years. These include 733 animals (mostly vertebrates and molluscs), 110 plants and one red alga. The extinction of dodo in Mauritius, quagga in Africa were notable extinctions in the recent years.

The species that became extinct in 2003 was the plant Nesiota elliptica, St. Helena Olive (a small tree in Saint Helena Island) in the South Atlantic Ocean. The IUCN red list of threatened species founded in 1964, is the worlds most comprehensive inventory of global conservation status of biological species.The IUCN Red List has listed 132 species of plants and animals from India as ‘Critically Endangered’.

Red List assign categories to each species. These are as follows

Extinct A taxon is extinct when there is no reasonable doubt that its last individual has died, e.g. dodo, Indian cheetah.
Extinct in the Wild (EW) A number of domesticated animals and plants have become extinct in the wild. A taxon is extinct in the wild when it is known to survive only under cultivation.
Critically Endangered (CR) A taxon is critically , endangered when it is facing an extremely high risk of extinction in the wild in immediate future (925 animals and 1014 plants), e.g, One horned rhinoceros.
Endangered (EN) A taxon is endangered when it is not critically endangered, but facing a very high risk of extinction in the wild in near future, e.g, Giant panda and polar bear.
Vulnerable (VU) A taxon is vulnerable when it is not critically endangered or endangered, but it is facing a high risk of extinction in the wild in the medium term future, e.g. sparrow.
Threatened Species is the one which is liable to become extinct if not allowed to realise its full biotic potential by providing protection from the exotic species, e.g. in black buck.
Low Risk (LR) A taxon is at low risk when evaluated, it does not qualify for any of the categories like critically endangered, endangered or vulnerable.
Data Deficient (DD) A taxon is data deficient when there is inadequate information to make a direct or indirect assessment of its risk of extinction based on its distribution or population status.
Not Evaluated (NE) A taxon is under the category of not evaluated, when it has not yet been assessed against above criteria.

Biodiversity Conservation:

Biodiversity Preservation Methods and Sites

A national park is a relatively large area reserved for the betterment of the wildlife. The habitats of native plant and animals becomes the site of scientific, educational and recreative interests along with maintenance of its aesthetic values.
Since, human intervention is nil or limited, the operating ecosystem remains unaltered and conserved.
It is also defined as an area where the highest authority take measures to prevent exploitation and enforce conservation measures.
A place where visitors are permitted to enter only in special conditions like inspirational, cultural and recreative purposes.

According to Myers, the key criteria for an area to be assigned as biodiversity hotspot are

It must contain atleast 0.5% or 1,500 of the world’s 3,00,000 species of vascular plants as endemics.
It should have lost atleast 70% of its primary vegetation.

Each biosphere reserve integrates human activities and has following zonation

Core zone Strictly protected.
Buffer zone Sustainable and recreation activities allowed.
Transition zone Anthropogenic activities like research and sustainable development allowed.
Zone of human encroachment Normal anthropogenic activities allowed.

Out of 18 biosphere reserves, 8 of them are a part of world network of Biosphere Reserves based on MAB Programme of UNESCO.

The objectives of this programme are

Conserving representative samples of ecosystems.
In situ conservation of genetic diversity.
Facilitating basic and applied research in ecology and environmental biology on site.
Create opportunities for environmental education k and training.
Promoting and creating awareness about sustainable management of living resources.
Promoting international cooperation.

Therefore, the biosphere reserves have three junctions, that includes

Conservation of ecosystems and genetic variations.
Promotion of sustainable economic and human development.
They serve as examples of education and training local, regional, national and international issues of sustainable development.

A protected area to be declared as a biosphere reserve should have the following essential features

Abundant genetic diversity should be present.
It should be unique in itself.
The area should be legally protected for long term.
Appropriate size for effective maintenance of natural populations so that there is no genetic drift.
Sufficient natural resource available for ecological research, education and training. It should be a natural home for the endangered species of plants and animals.

CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation

July 31, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 4 Question Answer Heredity and Variation

Heredity and Variation Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
The experimental plant material used by Mendel was
(a) cowpea
(b) garden pea
(c) wild pea
(d) sweet pea
Answer:
(b) garden pea

Question 2.
Which of the following characters is not among the seven characters considered by Mendel for his hybridisation experiments?
(a) Seed colour
(b) Pod shape
(c) Flower position
(d) Flower shape
Answer:
(d) Flower shape

Question 3.
Which law Mendel would not have proposed, if the phenomenon of linkage was known to him?
(a) Law of unit character
(b) Law of dominance
(c) Law of segregation
(d) Law of independent assortment
Answer:
(d) Law of independent assortment

Question 4.
The number of genotypes produced in F2-generation in Mendel’s monohybrid cross was
(a) 1
(b) 2
(c) 3
(d) 4
Answer:
(c) 3

Question 5.
In which of the crosses, half of the offsprings show dominant phenotype?
(a) Tt × Tt
(b) TT × tt
(c) Tt × tt
(d) TT × TT
Answer:
(c) Tt × tt

Question 6.
Two allelic genes are located on the
(a) same chromosome
(b) two homologous chromosomes
(c) two non-homologous chromosomes
(d) any two different chromosomes
Answer:
(b) two homologous chromosomes

Question 7.
Red (RR) Antirrhinum is crossed with white (rr) one. The F₁-hybrid is pink. This is an example of
(a) complete dominance
(b) codominance
(c) incomplete dominance
(d) complete recessive
Answer:
(c) incomplete dominance

Question 8.
In a dihybrid cross in F₂-generation, the parental types are far greater in number than the recombinants. This is due to
(a) linkage
(b) incomplete dominance
(c) multiple allelism
(d) complete dominance
Answer:
(a) linkage

Express in one or two word(s)

1. A pair of Mendelian factors (genes) that appear at a particular location on a particular chromosome and control the same characteristic.
Answer:
Alleles

2. Phenomenon where in the heterozygous condition an intermediate phenotype is observed.
Answer:
Incomplete dominance

3. The phenomenon of a single gene contributing to multiple phenotypic traits.
Answer:
Pleiotropy .

4. Genes which move together and do not show independent assortment.
Answer:
Linked gene

5. A cross between the F₁-hybrids with any one of the homozygous parents.
Answer:
Back cross

Correct the sentences, if required, by changing the underlined word (s) only

1. The process of transmission of characters through generations is known as variation.
Answer:
inheritance

2. In Mendel’s monohybrid cross, the dwarf phenotype is always homozygous.
Answer:
Correct statement

3. In Mendel’s dihybrid cross in F₂-generation, nine phenotypes are produced.
Answer:
four

4. The phenomenon of linkage disproved the principle of independent assortment.
Answer:
Correct statement

5. In a test cross, always dominant parent is used.
Answer:
recessive

6. The distance between genes in a constructed gene map is expressed as Mendel unit.
Answer:
Morgan

Fill in the blanks

1. Monohybrid cross in Regeneration yields ____ number of phenotypes.
Answer:
two

2. Monohybrid cross in Regeneration yields ____ number of genotypes.
Answer:
three

3. The name of scientist often coined with linkage is ____ .
Answer:
TH Morgan

4. Genotype of a plant showing the dominant phenotype can be determined by ____ cross.
Answer:
test

5. In a cross between AaBB and aaBB, the genotypic ratio in Ft-generation will be ____ .
Answer:
1 : 1

Short Answer Type Questions

Write notes on the following

Question 1.
Law of independent assortment
Answer:
It states that when two pairs of traits are combined in a hybrid, segregation of one pair of traits is independent to the other pair of traits. As in the dihybrid cross of Mendel the presence of new combinations, i.e. round-green and wrinkled-yellow suggests that the genes for shape of seed and colour of seed are assorted independently. The results (9:3:3:1), indicate that yellow and green seeds appear in the ratio of 9+3 : 3+1 = 3:1.
Similarly, the round and wrinkled seeds appear in the ratio of9 + 3:3+1 = 3:1.

This indicates that each of the two pairs of alternative characters viz yellow-green cotyledon colour is inherited independent of the round-wrinkled characters of the cotyledons. It means that at the time of gamete formation the factor for yellow colour enters the gametes ” independent of R or r, i.e. gene Y can be passed on to the gametes either with gene R or r.

Question 2.
Multiple alleles
Answer:
Multiple allelism and Inheritance of Blood Groups:
Each gene has alternative forms or allelomorphs. For example, the genes for rail and dwarf characters of pea plant arc ailcics or allelomorphs. Here, former is called normal or wild type and Iatcr as mutant type.
Sometimes, there may no be any aiternative form such mutation that results in complete elimination of a gene is known as null mutation. Sometimes silent mutation occurs in which mutation does not have any effect of all.

These mutations occur in wild gene in any direction with a possibility of formation of many alternative alleles. Some genes may occur in more than two allelic forms, i.e. a gene can mutate several times to produce several alternative expressions such genes are called multiple alleles.

Question 3.
Chromosomal basis of inheritance
Answer:
It was proposed independently by Walter Sutton and Theodore Boyen in 1902. They united the knowledge of chromosomal segregation with Mendelian principles and called it chromosornal theory of inheritance.
According to this theory

All hereditary characters must be with sperms and egg cells as they provide bridge from one generation to the other.
The hereditary factors must be carried by the nuclear material.
Chromosomes are also found in pairs like the Mendelian alleles.
The two alleles of a gene pair are located on homologous sites on the homologous chromosomes.

Question 4.
Codominance
Answer:
Codominance:
It is the phenomenon in which two alleles express themselves independently when present together in an organism. In other words, it is the phenomenon in which offspring shows resemblance to both the parents,
e.g. ABO blood grouping in humans.

Question 5.
Incomplete dominance
Answer:
Incomplete Dominance:
It is a phenomenon in which phenotype of the F₁-hybrid offsprings does not resemble any of the parent, but is an intermediate between the expression of two alleles in their homozygous state. Carl Correns was the one who reported incomplete dominance in plant Mirabilis jalapa. He showed the petal colour inheritance in this plant. Here, the phenotypic ratio deviates from Mendel’s monohybrid ratio but the parental characters reappear in F₂-generation.

Question 6.
Law of segregation
Answer:
This principle states that, though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other, such that a gamete receives only one of the two factors. Hence, the alleles do not show any blending and both the characters are recovered as such in the F₂-generation though one of these is not seen in the F₁-generation.

Question 7.
Linkage
Answer:
The genes of a particular chromosome show the tendency to inherit together. This phenomenon of genic inheritance in which genes of a particular chromosome show their tendency to inherit together, i.e tendency to retain their parental combination even in the offsprings is known as linkage.

Question 8.
Recombination
Answer:
They attributed this due to physical association of the two genes and coined the term ‘linkage’ to describe this physical association of genes on a chromosome and the term ‘recombination’ to describe the generation of non-parental gene combinations. Morgan performed a test cross by crossing heterozygous grey-bodied and long-winged with homozygous recessive black-bodied and vestigial-winged fly

Question 9.
Test cross
Answer:
A special back cross to the recessive parent is known as test cross. This method was devised by Mendel to determine whether the dominant phenotype is homozygous or heterozygous.

For example, in a monohybrid cross between violet colour flower (W) and white colour flower (w), the F₁-hybrid was a violet colour flower. If all the F₁-progenies are of violet colour, then the dominant flower is homozygous and if the progenies are in 1:1 ratio, then the dominant flower is heterozygous.
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 1

Question 10.
Back cross
Answer:
Back cross is a cross of F₁ -progeny back to one of their parents. In back cross, there can be two possibilities, i.e. F₁ -hybrid to be crossed with homozygous dominant parent or with homozygous recessive parent.
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 2

Differentiate between the following

Question 1.
Homozygous and Heterozygous
Answer:
Differences between homozygous and heterozygous are as follows

Homozygous	Heterozygous
It is a condition when both alleles of a gene are similar.	It is a condition when both alleles of a gene are dissimilar.
The genotype is expressed as TT or tt.	The genotype expressed as Tt.
They are true breeding to purelines.	They are not true breeding.
The gametes produced by them are similar in genotype.	The gametes produced by them are of two types, one with dominant allele and other with recessive allele.

Question 2.
Genotype and Phenotype.
Differences between phenotype and genotype are as follows
Answer:

Phenotype	Genotype
It refers to observable traits or characters.	It refers to the genetic constitution of an individual.
It results from expression of genes.	It constitutes single gene pair or sum total of all the genes.
The phenotypic ratio of Mendel’s monohybrid cross is 3 : 1.	The genotypic ratio of Mendel’s monohybrid cross is 1:2:1.
It may change with age and environment.	It remains the same throughout the life of an individual.

Question 3.
Dominant genes and Recessive genes.
Answer:
Differences between dominant genes and recessive genes are as follows

Dominant genes	Recessive genes
When an allele expresses itself in the presence of its recessive allele, it is called dominant trait.	It can only express in the absence of its dominant allele and remain masked in its presence.
Dominant allele forms a complete functional enzyme due to which complete polyeptide is formed to express.	Recessive allele forms incomplete polypeptide enzyme due to which non-functionai polypetide is formed and fails to express completely.

Question 4.
Back cross and Test cross.
Answer:
Differences between back cross and test cross are as follows

Back cross	Test cross
It is a cross involving F₁-progeny and either of the parents.	It is a cross involving
It is used by scientists to improve a breed or variety of plant or animal.	F₁-individual and its recessive parent.

Question 5.
Qualitative inheritance and Quantitative inheritance.
Answer:
Differences between qualitative inheritance and quantitative inheritance are as follows

Qualitative inheritance	Quantitative inheritance
It deals with the inheritance of qualitative characters.	It deals with the inheritance of quantitative characters.
Each character is controlled by one pair of contrasting alleles.	Each character is controlled by more than one pair of non-allelic genes (Polygenes).
Each character has two distinct expressions, i.e. exhibits two distinct phenotypes.	Each character has an intergrading range of phenotypes.
The degree of expression remains the same whether the character is controlled by one or both the dominant genes.	The degree of expression depends on the number of the dominant genes.
Phenotypic expression is not affected by the environment.	Phenotypic expression is influenced by environmental factors.
Monogenic inheritance exhibits discontinuous pattern of inheritance.	Polygenic inheritance represents continuous pattern of inheritance.
F₁-individuals resemble the dominant parent.	F₁-individuals exhibit intermediate expression between the two parents.
F₂-individuals exhibit 3:1 ratio. Intermediate expressions are not found.	In F₂-generation, individuals with intermediate genotype and phenotype are maximum.
Examples of monogenic or qualitative inheritance are yellow or green coat color or round or wrinkled seed character in pea seeds.	Examples of polygenic or quantitative inheritance are height, weight, intelligence and skin color in human beings, milk yield in cattle and egg production in poultry.

Long Answer Type Questions

Question 1.
Give an account of Mendel’s monohybrid cross. What inference did Mendel draw from this experiment?
Answer:
Monohybrid Cross
The study of inheritance of a single pair of alleles or factors of a trait at a time (monohybrid cross) is called one gene inheritance. When a cross is made between pure tall and pure dwarf plant (for purity, the pureline is taken into consideration) in F₁-generation, all plants will be tall.

When F₁ -plants are self-pollinated, then in F₂-generation both tall and dwarf plants are found in approximate ratio of 3 : 1.

The dwarf plants of F₂ on self-pollination, produce dwarf plants generation after generation, while among tall plants, only 1 /3rd show this character generation after generation (pureline) and rest 2/3rd produce tall and dwarf in 3 : 1 ratio again (F₃ -generation).

Explanation Mendel’s monohybrid cross explained that in each main pair of alternative character one is expressed and other is masked.
The character which is expressed in F₁-generation is called dominant and the one which is not expressed is called recessive.
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 3
The monohybrid cross between tail and dwarf

In F₂-generation, the genotypic ratio is 1 : 2 : 1 and phenotypic ratio is 3 : 1. Mendel came to the conclusion that progeny possessing similar factors is called homozygous and the one which is hybrid is called heterozygous.

Mendel used english letters to record his observations of breeding experiments. He assigned capital letters for dominant characters and small letters for recessive characters which tabulated in the given below table

Characters	Dominant	Recessive
Seed shape	Round (R)	Wrinkled (r)
Seed colour	Yellow (Y)	Green (y)
Pod shape	Full (F)	Constricted (f)
Pod colour	Green (G)	Yellow (g)
Flower/Pod position	Axial (A)	Terminal (a)
Seed coat colour/Flower colour	Red/Violet (R/V)	White (r/v)
Plant height	Tall (T)	Dwarf (t)

Based on his observations on monohybrid crosses, Mendel proposed two general rules in order to consolidate his understanding of inheritance in monohybrid crosses.

Based on the Mendel’s observations, the German scientist Carl Correns formulated certain principles of heredity. These now known as Mendel’s laws of inheritance or the principles or laws of inheritance.
These are
Principle of Dominance:
It states that when two contrasting alleles for a character come together in an organism, only one is expressed completely and shows visible effect. This allele is called dominant and the other allele of the pair which does not express and remains hidden is called recessive.

For example, in the monohybrid cross when dwarf plant is crossed with tall plant, the Frgeneration are all tall plants. This shows that allele for tallness is dominant.

Question 2.
State and explain Mendel’s laws of inheritance.
Answer:
Following inferences were made by Mendel based on his observations
1. He proposed that some ‘factors’ passed down from parent to offsprings through the gametes over successive generations. Now-a-days, these factors are known as genes. Genes are hence, the units of inheritance. Genes which code for a pair of contrasting traits are known as alleles or allelomorphs, i.e. they are slightly different forms of the same gene.

2. Genes occur in pairs in which, one dominates the other called as the dominant factor or the gene which expresses itself, while the other remains hidden and is called recessive factor.

3. Allele can be similar in case of homozygous (TT or tt) and dissimilar in case of heterozygous (Tt).

4. In a true-breeding tall or dwarf pea variety, the allelic pair of genes for height are identical or homozygous.

5. TT and tt are called genotype (sum total of heredity or genetic make up) of the plant, while the term tall and dwarf are the phenotype.

6. When tall and dwarf plants produce gametes by process of meiosis, the alleles of the parental pair segregate and only one of the alleles gets transmitted to a gamete. Thus, there is only 50% chance of a gamete containing either allele, as the segregation is a random process.

7. During fertilisation, the two alleles, ‘T’ from one parent and V from other parent are united to produce a zygote, that has one ‘T’ and one allele or the hybrids have Tt.

8. Since, these hybrids contain alleles which express contrasting traits, the plants are heterozygous.

Question 3.
What do you mean by back cross and test cross? Explain test cross through an example.
Answer:
Back cross is a cross of F₁ -progeny back to one of their parents. In back cross, there can be two possibilities, i.e. F₁ -hybrid to be crossed with homozygous dominant parent or with homozygous recessive parent.
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 2

A special back cross to the recessive parent is known as test cross. This method was devised by Mendel to determine whether the dominant phenotype is homozygous or heterozygous.

Question 4.
Describe Mendel’s dihybrid cross.
Answer:
When two or more than two characters are taken in a cross it is called as polyhybrid cross, e.g. dihybrid cross, trihybrid cross, etc. A dihybrid cross is a cross involving two pairs of contrasting characters. For example, when a cross is made between yellow-round and wrinkled green seeds (both pureline homozygous), plants with only yellow round seeds are seen in F₁-generation but in F₁-generation, four types of combinations are observed.

Two of these combinations are similar to the parental combinations and others are new combinations. These are round green and wrinkled yellow.
The cross can be seen as shown in the figure
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 4
Phenotypic Ratio Round yellow : Round green : Wrinkled yellow : Wrinkled green = 9 : 3 : 3 : 1
Genotypic Ratio 1 : 2 :2 : 4 : 1 : 2 : 1 : 2 : 1

The ratio of four combinations in F₂-generation comes out to be 9 (round, yellow) : 3 (round, green) : 3 (wrinkled, yellow) : 1 (wrinkled, green). This ratio is called phenotypic dihybrid ratio. Phenotypic ratio of dihybrid test cross is 1 : 1 : 1 : 1.

Mendel’s Postulate Based on Dihybrid Cross:
Based on the result obtained from dihybrid crosses or two gene interaction, Mendel proposed the fourth postulate, i.e. law of independent assortment.

Question 5.
Give an account of linkage and recombination.
Answer:
Linkage, Crossing Over and Recombination:
According to ‘chromosomal theory of inheritance’, the chromosomes are vehicles of inheritance. Hence, the number of genes per individual for exceed the number of chromosomal pairs, i.e. each chromosome bears many genes. These genes are arranged in linear fashion over the chromosome and cannot show independent assortment.

In other words, we can say that the genes of a particular chromosome show the tendency to inherit together. This phenomenon of genic inheritance in which genes of a particular chromosome show their tendency to inherit together, i.e tendency to retain their parental combination even in the offsprings is known as linkage.

Morgan and his group observed in Drosophila that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type.

They attributed this due to physical association of the two genes and coined the term ‘linkage’ to describe this physical association of genes on a chromosome and the term ‘recombination’ to describe the generation of non-parental gene combinations. Morgan performed a test cross by crossing heterozygous grey-bodied and long-winged with homozygous recessive black-bodied and vestigial-winged fly. They obtained the following results

Phenotype	Per cent of occurrence
Grey body long wing	41.5
Black body vestigial wing	41.5
Grey body vestigial wing	8.5
Black body long wing	8.5

This result was not in accordance with Mendel’s law of inheritance. Now suppose in order to explain, we assume the alphabets G and g for grey and black body colours and L and 1 for long and vestigial wings, respectively.

Thus, linkage is a phenomenon of genic inheritance in which genes of a particular chromosome show their tendency to inherit together.
Morgan and his group also found that even when genes were grouped on the same chromosome, some genes were tightly linked, i.e. linkage is stronger between two genes, if the frequency of recombination is low (cross-A). Whereas, the frequency of recombination is higher, if genes are loosely linked, i.e. linkage is weak between two genes (cross-B) as given in figure
CHSE Odisha Class 12 Biology Solutions Chapter 5 Heredity and Variation 5

Linkage : Results of two dihybrid crosses conducted by Morgan. Cross ‘A’ shows crossing between genes y and w ; Cross ‘B’ shows crossing between genes w and m. Here, dominant wild type alleles are represented with (+) sign in superscript

Those traits present on same chromosome, which do not show any production of recombinants are completely linked which is known as complete linkage and it is very rare.

Linkage Groups:
All the genes linked together in a single chromosome constitute a linkage group. The number of linkage group in an organism is equal to their haploid number of chromosomes. This hypothesis was proved by TH Morgan by his experiments on Drosophila.

Morgan and his group hybridised yellow-bodied and white-eyed females with brown-bodied and red-eyed males (wild type) and intercrossed their F₁-progeny (cross A). It was observed that the two genes did not segregate independently of each other and the F₂-ratios deviated significantly from 9:3:3 :1 ratio.

In F₂-generation, parental combinations were 98.7% and the recombinants were 1.3%. In another cross (cross-B), between white-bodied female fly with miniature wing and a male fly with yellow body and normal wing, parental combinations were 62.8% and recombinants were 37.2% in F₂-generation. Thus, it was proved from the crosses that the linkage between genes for yellow body and white eyes is stronger than the linkage between the white body and miniature wing.

Chromosome Maps or Linkage Maps:
Alfred Sturtevant (Morgan’s student) used the frequency of recombination between gene pairs on the same chromosome as a measure of the .distance between genes and ‘mapped’ their position on the chromosome. Genetic maps are now used as a starting point in the sequencing of whole genomes as done in case of human genome sequencing project.

The frequency of recombination Cross Over Value (COV) is calculated by using the formula

A linkage or genetic chromosome map is a linear graphic representation of the sequence and relative distances of the various genes present in a chromosome. 1% crossing over between two linked genes is known as 1 map unit or Morgan (after TH Morgan, who is considered as ‘Father of Experimental Genetics’).

CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem

July 30, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 15 Question Answer Ecosystem

Ecosystem Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
Forests represent …………. ecosystem.
(a) aquatic
(b) terrestrial
(c) estuarian
(d) grassland
Answer:
(b) terrestrial

Question 2.
Decomposers are generally ……………..
(a) green plants
(b) microorganisms
(c) phytoplanktons
(d) insects
Answer:
(b) microorganisms

Question 3.
Man is a ……………..
(a) herbivore
(b) carnivore
(c) omnivore
(d) producer
Answer:
(c) omnivore

Question 4.
Ecological efficiency is less than …………….. per cent.
(a) 1
(b) 10
(c) 5
(d) 0.5
Answer:
(d) 0.5

Question 5.
The efficiency for energy transfer from one trophic level to another is nearly …………….. per cent.
(a) 1
(b) 10
(c) 5
(d) 20
Answer:
(b) 10

Question 6.
Pyramid of …………….. cannot be inverted.
(a) energy
(b) biomass
(c) number
(d) ecosystems
Answer:
(a) energy

Question 7.
Succession that starts at …………….. habitat is called hydrosere.
(a) sandy
(b) rocky
(c) aquatic
(d) xeric
Answer:
(c) aquatic

Question 8.
Succession that starts at sandy habitat is called …………….. .
(a) halosere
(b) lithosere
(c) psammosere
(d) hydrosere
Answer:
(c) psammosere

Express in one or two words

Question 1.
What can be called primary consumers?
Answer:
Herbivores

Question 2.
What is called to decomposers living on dead, decaying substratum?
Answer:
Saprophytes

Question 3.
Through which process is energy lost from living organisms?
Answer:
Respiration

Question 4.
Which type of ecological pyramid is never inverted?
Answer:
Pyramid of energy

Question 5.
What is called to the process of creation of bare area?
Answer:
Nudation

Question 6.
What is the form of climax forest called?
Answer:
Dense climax forest

Correct the statement, in each bit without changing the underlined words

Question 1.
Pond represents a forest ecosystem.
Answer:
Pond represents an aquatic ecosystem.

Question 2.
Ecosystem has structural and energy aspects.
Answer:
Ecosystem has structural and functional aspects.

Question 3.
Biogeochemical cycle may be otherwise called energy cycle.
Answer:
Biogeochemical cycle may be otherwise called nutrient cycle.

Question 4.
All heterotrophs are capable of photosynthesis.
Answer:
All autotrophs are capable of photosynthesis.

Question 5.
Animals are responsible for utilising dead, decaying substances, thereby cycling of materials becomes feasible.
Answer:
Microbes are responsible for utilising dead, decaying substances, thereby degrade detritus into smaller particles.

Question 6.
Flow of nutrients is unidirectional.
Answer:
Flow of energy is unidirectional.

Question 7.
Net primary productivity is calculated by taking into consideration gross primary productivity and photosynthesis.
Answer:
Net primary productivity is calculated by taking into consideration gross primary productivity and respiration loses.

Question 8.
Food-chain shows a complicated net-like inter-relationship in trophic levels.
Answer:
Food web shows a complicated net-like inter-relationship in trophic levels.

Question 9.
Pyramid of biomass takes into consideration the number of organisms in each trophic level.
Answer:
Pyramid of biomass takes into consideration total weight of organisms in each trophic level.

Question 10.
Pyramid of energy is always inverted.
Answer:
Pyramid of energy can never be inverted.

Question 11.
A stable community shows high species dominance.
Answer:
A stable community shows less species dominance.

Question 12.
Primary succession starts where there was living matter previously.
Answer:
Primary succession starts on a substratum where there was no living matter previously.

Fill in the blanks

Question 1.
Green plants are called …………… as they fix CO₂.
Answer:
autotrophs

Question 2.
In forest ecosystem, pyramid of number is ………….. type.
Answer:
inverted

Question 3.
Common decomposers form ………… ecosystem.
Answer:
Detritivorous

Question 4.
Secondary products are called ………… in a food chain.
Answer:
Detritus

Question 5.
The second trophic level in pond is …………….
Answer:
herbivores

Short Answer Type Questions

Write short notes on each of the following

Question 1.
Ecosystem
Answer:
An ecosystem is a basic functional unit that includes the whole community in a given area (biotic component) interacting with the abiotic factors.
Ecosystem is normally an open system because there is a continuous gain and loss of energy and materials from this system.
The term ecosystem’ was first used by AG Tansley in 1935 to describe the whole complex of organisms living together as sociological units and their habitats.
The ecosystem is also called as biocoenosis (Mobius; 1877), microcosm (Forbes; 1887) and biogeocoenosis (Sukachey). It is also known as ecocosm or biosystem.

Question 2.
Ecesis
Answer:
Ecesis It is successful germination of propagules into the bare area. The germination of seeds and spores produces new seedlings or new plants. As a result, some individuals of a species successfully get established in the bare area.

Question 3.
Ecological pyramid
Answer:
These are the diagrammatic illustrations of connection between different trophic levels in terms of energy, biomass and number of organisms. They represent the standing crops at each trophic level.

The base of each pyramid represents the producers or the first trophic Level and its apex represents tertiary or top level consumers. There are three ecological pyramids that are usually studied.

Question 4.
Food web
Answer:
Food web is the network of food chains which become interconnected at various trophic levels. In any complex food web, one can recognise several different trophic levels. In a food web, a given species may occupy more than one trophic level.
The complexity of food web is in direct relation with the stability of the ecosystem. Such type of ecosystem is not destroyed naturally and is sustained for a long time.

Question 5.
Plant succession
Answer:
Plant Succession
The process of changes in the habitat accompanied by the change of vegetation, one after the another is called plant succession. Its basic concept lies in the fact that the interaction between the habitat and the plants colonising the habitat results in some changes in the climate which may not be suitable for the existing plant community.
Thus, new plant community evolves which can survive the changed environment and replace the old ones.

Question 6.
Phytoplankton
Answer:
Phytoplanktons are small aquatic plants that form first stage of hydrosere. They include green flagellates, green algae, blue-green algae, etc. Their death in water bodies build up the amount of organic matter. They contribute about 50% available oxygen in atmosphere.

Question 7.
Nudation
Answer:
This is a process by which a bare area is created. The reasons behind the creation of a bare area may be topographic (soil erosion, land slide, volcanic activity); – climatic (glaciers, storms, frost, fire, etc.) or biotic (anthropogenic activities like industrialisation, agriculture, etc.).

Question 8.
Food chain
Answer:
Types of Food Chain:
There are mainly two types of food chain
(i) Grazing Food Chain (GFC) It begins with the producers, which capture the solar energy and feed the energy into the food chain through
photosynthesis, e.g.

Grass → Grasshopper → Frog → Snake → Eagle
Grass (Producer) → Goat (Prirnazy consumer) → Man (Secondary consumer)

In an aquatic ecosystem, the GFC is the major channel for energy flow, e.g.
Phytoplanktons → Crustaceans → Fishes

(ii) Detritus Food Chain (DFC) It begins with dead organic matter and is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria.
Dead leaves (Producer) → Woodlouse (Primary consumer) → Black bird (Secondary consumer)

Question 9.
Climax forest
Answer:
Forest (climax) stage The climax vegetation of trees depends on the climate of the region. If the climate is dry, trees like Acacia grow. In relatively moist and wet climate, mesophytic trees grow and a dense climax forest is formed. Along with the changes in the plant life in a xerosere (as also in a hydrosere), there is also a change in the animal life. The colonisation starts with ants and spiders and goes upto a variety of arthropods, birds and mammals by the fime the climax community is formed.

Question 10.
Species diversity
Answer:
It is the measure of the diversity within an ecological community that incorporates both species richness that is, the number of species in a community and the evenness of the species abundance. A community is more stable when its species diversity is high.

Differentiate the following with at least 3 valid points

Question 1.
Parasite and Saprophyte
Answer:
Differences between parasites and saprophytes are as follows

Parasites	Saprophyte
They derive nutrition from the host body.	They derive nutrition from dead-decaying materials.
Their body is not well-developed with complete-lack of sense organs.	Their body is well-developed.

Question 2.
Producers and Consumers
Answer:
Differences between producers and consumers are as follows

Producers	Consumers
These are green plants who prepare food material in the presence of sunlight.	They are mostly animals who depend on plants or other animals for food.
They are called autotrophs.	They are called heterotrophs.
They form the first trophic level, e.g. green plants.	They form second or third trophic level, e.g. animals.

Question 3.
Food chain and Food web
Answer:
Differences between food chain and food web are as follows

Food chain	Food web
It is a single straight pathway through which food energy travels in the ecosystem.	It consists of number of interconnected food chains through which food energy passes in the ecosystem.
Members of higher trophic level feed upon a single type of organisms of lower trophic level.	Members of higher trophic level can feed upon a number of alternative organisms of the lower trophic levels.
The presence of separate or isolated food chains adds to the instability of the ecosystem.	The presence of food webs increases the stability of the ecosystem.
It does not add to adaptability and competitiveness of the organisms.	Food webs increase the adaptability and competitiveness of the organisms.
Only the members of one trophic level compete for obtaining the same food.	Competition is among members of different species. It is less severe as a number of alternate foods are available.

Question 4.
Herbivores and Predators
Answer:
Differences between herbivores and predators are as follows

Herbivores	Predators
They eat plants.	They eat flesh.
Body is comparatively weak.	Body is strong.
Canine teeth are absent, primolars are well-developed, e.g. cow.	Canines are well-developed for flesh cutting, e.g. lion.

Question 5.
Primary succession and Secondary succession
Answer:
Differences between primary succession and secondary succession are as follows

Primary succession	Secondary succession
It occurs in an area which has been bare from the beginning.	It occurs in an area which has been denuded recently.
Soil is absent at the time of beginning of primary succession.	Soil is present in the area where secondary succession begins.
There is no humus in the beginning.	Humus is present from the very beginning.
Reproductive structures of any previous community are absent.	Reproductive structures of the previous occupants are present in the area.
In the beginning the environment is very hostile.	The environment is favourable from the beginning.
Serai communities are many.	Serai communities are.a few.
It takes a long time for completion, 1000 years or more.	It takes less time for completion, 50-200 years.

Question 6.
Gross primary productivity and Net primary productivity
Answer:
Differences between gross primary productivity and net primary productivity are as follows

Gross primary productivity	Net primary productivity
It is the amount of organic matter synthesised by producers per unit area in unit time.	It is the amount of organic matter stored by producers per unit area in unit time.
It refers to the total productivity including the energy utilised for respiration by the producers.	It refers to the net productivity that is converted to organic matter excluding the energy utilised for respiration by the producers.
GPP=Rate of increase in body weight or rate of organic matter synthesised by producers + the rate of respiration and other damages.	NPP=Rate of organic matter synthesised by photosynthesis by producers= the rate of energy utilised for respiration and other damages.

Question 7.
Pyramid of biomass and Pyramid of numbers
Answer:
Differences between pyramid of biomass and pyramid of numbers are as follows

Pyramid of biomass	Pyramid of numbers
It represents the biomass of producers, consumers, first level carnivores, etc.	It helps to tell about the relative numbers of organisms at each of the 4 trophic levels-producers, consumers and two levels of predators in a forest or lake ecosystem.
It is generally pyramidal in shape, but appears inverted like in a pond ecosystem where phytoplanktons support a large number of zooplankton.	It may become inverted due to existence of parasites or when a single tree supports much smaller organisms.
Difficult to determine because it would be a time consuming job.	It is easy to determine.

Question 8.
Abiotic components and Biotic components
Answer:
Differences between biotic components and abiotic components are as follows

Biotic components	Abiotic components
They represent the living organisms present in an ecosystem.	They represent non-living structures and factors of the ecosystem.
Biotic components include producers, consumers and decomposers.	Abiotic components include inorganic nutrients, organic remains and physical factors.
They build up and utilise chemical energy for their functioning.	Species diversity and Species dominance Differences between species diversity and species dominance are as follows
For their body building, they obtain inorganic nutrients and energy from abiotic components.	They are influenced by physical form of energy as light and heat.

Question 9.
Species diversity and Species dominance
Answer:
Differences between species diversity and species dominance are as follows

Species diversity	Species dominance
It is the presence of different species in an area, hence, species richness is abundant.	It is the presence of single species in an area, hence species richness is negligible.
It forms a stable community.	It forms an unstable community.
Resources of community do not deplete due to the absence or very less competition among different species	Community resources deplete very fast due to competition with same species.

Long Answer Type Questions

Question 1.
What is ecosystem? Describe the different components of ecosystem.
Answer:
Ecosystem is considered as an interactive system, where biotic and abiotic components interact with each other via energy exchange and flow of nutrients. An ecosystem can be either natural or artificial. Natural ecosystems These are capable of maintaining and operating themselves, without the interference of man. They are further classified as
CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem 1
Artificial ecosystems These are maintained and manipulated by man for different purposes, e.g. cropland, aquarium, etc.

Ecosystem Components:
An ecosystem has two major components, abiotic (non-living) and biotic (living), which can be further classified as follows
CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem 2
Biotic Components
In order to survive and maintain themselves, living organisms require various nutrients. On the basis of nutritional requirement of an organism, they can be divided into three types of organisation as follows
(i) Producers
The self-productive (autotrophic) living components that manufacture organic molecules and living protoplasm by using the inorganic compounds from the surrounding are called producers.

These can be further divided into two types

Photoautotrophs They obtain energy from the sunlight by the process called photosynthesis, e.g. green plants, photosynthetic bacteria, etc.
Chemoautotrophs These are chemosynthetic organisms that utilise hydrogen sulphide (H₂S) and bond energy derived from inorganic components, e.g sulphur oxidizing bacteria (Beggiatoa).

(ii) Consumers
The heterotrophic organisms that directly or indirectly organic materials manufactured by autotrophs are called consumers. These can be further categorised as

Primary consumers They directly consume the organic compounds synthesised by autotrophs, e.g. mammalian herbivores (predators), insect herbivores (parasites), etc.
Secondary consumers They derive organic compounds by feeding upon herbivores and small carnivores, e.g. mammalian carnivores (predators).

(iii) Decomposers
The saprophytic organisms that breakdown organic waste products into inorganic substances are called decomposers. They play a vital role in nature as they convert complex chemicals to simpler forms, e.g. microorganisms found in rotten and decaying organic materials.

Abiotic Components :
These are the non-living components that are mostly found in the utilisable form. They can be further ‘divided as follows

Inorganic nutrients They form physical environment, e.g. carbon (C), nitrogen (N), hydrogen (H), etc.
Organic compounds They provide nutrients, e.g. soil.
Environmental factors They provide energy, e.g. air, temperature, etc.

Interaction of biotic and abiotic components results in the formation of a functional structure that is an exclusive characteristic of each type of ecosystem.
The two important structural features of an ecosystem are

Species composition It is calculated by the identification and enumeration of plant and animal species of an ecosystem.
Stratification It is the vertical distribution of different species occupying different levels in an ecosystem, e.g. trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom (third) layers.

Question 2.
Give an account of energy flow in an ecosystem.
Answer:
Energy Flow Efficiency in an Ecosystem:
Energy transfer from one trophic level to next is governed by Lindemann’s law of trophic efficiency.
Tindeman in 1942 stated that in each step of food chain when food energy is transferred from one trophic level to the next higher trophic level, some energy is lost as heat and only 10% energy of net primary productivity is transferred to the next level.
CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem 3
Energy flow through different trophic levels

Lindemann demonstrated that plants convert solar energy into chemical energy (i.e. carbohydrates). This conversion follows the first law of thermodynamics where one form of energy is converted into another form and it is neither created nor destroyed. But, when this fixed energy is transferred from plants to next trophic level, 90% of it gets lost and only 10% energy is transferred to every successive trophic level.

Question 3.
Write a brief note about ecosystem services.
Answer:
Ecosystem Services
Healthy ecosystems are the base for a wide range of economic, environmental and aesthetic goods and services. Ecosystem services are the products of ecosystem processes, e.g. healthy forest ecosystem purifies air and water, mitigates droughts and floods, cycles nutrients, generates fertile soils, provides wildlife habitat, maintains biodiversity, pollinates crops, provides storage site for carbon and also provides aesthetic, cultural and spiritual values.

Although it is difficult to find out the monitory value of all these services, still it is reasonable to think that biodiversity should carry a hefty price tag.

Robert Constanza and his colleagues recently have tried to put price tag on the nature’s life-support services. Researchers have put a price tag of US $ 33 trillion a year on these fundamental ecosystem services, which we utilise for free. This is almost twice the value of global Gross National Product (GNP), which is of US $ 18 trillion. Out of the total cost of various ecosystem services, soil formation accounts for 50%.

Contribution of other services like recreation and nutrient cycling are less than 10% each. The cost of climate regulation and habitat for wildlife are about 6% each.

The popular definition of ecosystem services was given by United Nation 2005 Millennium Ecosystem Assessment (MEA) after a four year long study involving more than 1300 scientists worldwide. In 2005, MEA defined ecosystem services as benefits people obtain from ecosystem and they distinguished four categories of ecosystem services.
These are described in detail below
1. Provisioning Services
It includes the products that are obtained from ecosystem, e.g. genetic resources, food, fibre and freshwater.

2. Regulating Services
It includes the benefits that are obtained from the regulation of ecosystem processes, e.g.

Carbon sequestration and climate regulation.
Waste decomposition and detoxification.
Purification of water and air.
Crop-pollination.
Pest and disease control.

3. Supporting Services
It includes the processes that are necessary for the production of all other ecosystem services, e.g.

Nutrient dispersal and cycling.
Seed dispersal.
Primary production.

4. Cultural Services
It includes non-monetary benefits that we obtain from the ecosystem, e.g.

Cultural, intellectual and spiritual inspiration.
Recreational experiences (including ecotourism).
Scientific discovery.

Study of Ecosystem Services:
The study of ecosystem services includes the following steps

Identification of Ecosystem Services Providers (ESPs).
Determination of community structural aspects that influence house ESPs, function.
Assessment of key environmental (abiotic) factors influencing the provision of services.
Measurement of spatial and temporal scales ESPs and their services.

Examples of Ecosystem Services:
These include carbon cycle, pollination, oxygen release, etc.
I. Carbon-Fixation
The atmospheric carbon is fixed by the following three means

Natural carbon-fixation It occurs through biological, chemical and physical processes.
Artificial carbon-fixation It occurs through saline aquifers, reservoirs, ocean water, ageing oil fields, sea weed cultivation in oceans, etc.
Biological carbon-fixation It occurs through reforestation, urban forestry, wetland restoration and agriculture.

Carbon-fixation is helpful in following ways

The long term storge of CO₂ helps to reduce its harmful effects like global warming, climate chage, etc.
It helps to slow down the accumulation of greenhouse gases in atmosphere and marine bodies.

II. Pollination
It is the process of pollen transfer by different agents so, that a plant can reproduce sexually.
It is helpful in following ways

15-30% of crop plants are pollinated by insects like bees. For this reason, many farmers in USA import non-native bees which ensures proper pollination within 1-2 km radius.
In California, wild bees establish behavioural interactions with honeybees so, as to enhance the pollination service.

III. Oxygen Release
Oxygen is required by various life forms for respiration.
The major sources of oxygen include

Planktons and weeds in oceans About 50% of available oxygen is produced by planktons of marine ecosystem.
Trees Plants absorb CO₂ for photosynthesis and release oxygen. The net production of O₂ by a healthy tree depends upon its species, size, health and location.

CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment

July 28, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 14 Question Answer Organisms and Environment

Organisms and Environment Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
A population is a group of
(a) individuals in a species
(b) species’in a community
(c) individuals in a family
(d) communities in an ecosystem
Answer:
(a) individuals in a species

Question 2.
Exponential growth occurs when there is
(a) a great environmental resistance
(b) a fixed carrying capacity
(c) no biotic potential
(d) no environmental resistance
Answer:
(d) no environmental resistance

Question 3.
In a population, unrestricted reproductive capacity is called as
(a) carrying capacity
(b) birth rate
(c) biotic potential
(d) fertility rate
Answer:
(b) birth rate

Question 4.
Two opposite forces operate in the growth and development of a population. One of them is related to the ability to reproduce at a given rate. The force opposite to it is called
(a) environmental resistance
(b) mortality
(c) fecundity
(d) biotic control
Answer:
(b) mortality

Question 5.
The carrying capacity of a population is determined by its
(a) population growth rate
(b) mortality
(c) limiting resources
(d) natality
Answer:
(c) limiting resources

Question 6.
Which of the following at a conduit for energy transfer across trophic levels?
(a) mutualism
(b) parasitism
(c) protocooperation
(d) predation
Answer:
(d) predation

Question 7.
Phenomenon of inhibition of growth of one species by other species through secretion of some chemicals is termed as
(a) commensalism
(b) allelopathy
(b) mutualism
(d) predation
Answer:
(b) allelopathy

Question 8.
Predation performs all, except
(a) transfer of energy
(b) loss of sense organs
(c) keeps prey population under control
(d) maintains species diversity
Answer:
(b) loss of sense organs

Question 9.
Two important factors that influence the life of organisms are
(a) soil, temperature
(b) soil, light
(c) light, water
(d) water, temperature
Answer:
(c) light, water

Question 10.
Ecology describes
(a) interactions between living organisms only
(b) intraspecific competitions only
(c) interactions between members of single species
(d) interactions of organisms and abiotic components around
Answer:
(d) interactions of organisms and abiotic components around

Express in one or two words

Question 1.
Study of interrelationship between the environment and a plant species.
Answer:
Ecology

Question 2.
Amount of water vapours actually present in the air at any given time.
Answer:
Humidity

Question 3.
The total amount of water in the soil, except the gravitational water.
Answer:
Holard

Question 4.
Association of fungi and algae.
Answer:
Lichen

Question 5.
The study of soil.
Answer:
Pedology

Question 6.
Vegetation where the annual rainfall is more than 50 inches.
Answer:
Grassland

Correct the sentences changing the underlined word only

1. Plants those grow in soil and mud are xerophytes.
Answer:
mesophytes

2. Sunken stomata is a characteristic of hydrophytes.
Answer:
xerophytes

3. Air pockets are found in mesophytes.
Answer:
hydrophytes

4. The pre-reproductive mass is found more in urn- shaped pyramid.
Answer:
triangular

5. Population consists of different kinds of species.
Answer:
Community

Fill in the blanks

1. Shallow water region present on the edge of lakes is called …………. .
Answer:
littoral zone

2. The most relevant ecological factor is …………….. .
Answer:
light

3. Mortality and …………. contribute to a decrease in population density.
Answer:
emigration

4. J-shaped curve represents ………… growth.
Answer:
exponential

5. Geometric representation of age structure is a characteristic of ………..
Answer:
population

Short Answer Type Questions

Question 1.
Camouflage
Answer:
Camouflage It is the act of hiding the identify either by colour changes or by making animals or objects hard to see.
Some species of insects and frogs are cryptically coloured (camouflaged) to avoid being detected easily by predators.

Question 2.
Edaphic factor
Answer:
Edaphic factor An edaphic factor relating to physical or chemical composition of the soil found in a particular area, e.g. soil pH, porosity, water holding capacity, etc.

Question 3.
Habitat
Answer:
Environment is termed as sum total of all external conditions which influence the organisms in term of survival and reproduction. Habitat is a natural abode or locality where a plant/ animal grow, based on the environment, the differences in the vegetation and species of different places are observed.

Each organism plays an important role in its surrounding. Niche is the role of an organism plays in its ecosystem. In other words, we can say that niche is how an organism makes a living, interacts with other organisms and helps in cycling of nutrients.

Question 4.
Temperature
Answer:
Temperature
It is the most ecologically significant environmental factor. It varies seasonally on land and decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from sub-zero levels in polar areas and high altitudes to > 50°C in tropical deserts in summer. There are also certain unique habitats such as thermal springs, deep sea hydrothermal vents where the average temperature exceeds 100°C.

Question 5.
Biomes
Answer:
Biomes The large unit of ecology which consist of major vegetation type and associated fauna in a particular climatic zone is called biome, e.g. sea coast, deserts. Deciduous forest are the major biomes of India.

Question 6.
Population
Answer:
The term ‘population’ can be defined as a group or assemblage of organisms of the same species living in a particular area at a given time.
For example, the lion population of the Gir forest or the peacock population of India, etc.

The population may be subdivided into demes or local populations, which are a group of interbreeding organisms. It is the smallest collective unit of a plant or animal population.
The other is metapopulation, which consists of whole set of local populations connected by dispersing individuals.

Question 7.
Competition
Answer:
It is generally believed to occur when closely related the two individuals of species compete for the same resources that are limiting. This can happen between the members of the same species, i.e., intraspecific or different species, i.e. interspecific.

Question 8.
Abiotic factors
Answer:
Abiotic factors The non-living factors which influence an ecosystem and the organisms are called abiotic factors. It can determine which species of organism will survive in an given environment.

Question 9.
Population density
Answer:
Population Density
This refers to the size of population to a unit space at a particular time. This can be measured is several ways an mentioned below

Abundance (absolute number in population).
Numerical density (number individuals per unit area).
Biomass density (biomass per unit area).

Question 10.
Necessity of adaptations
Answer:
Necessity of adaptations Adaptations take a lot of time to evolve. They are necessary because they help the organism to fit in to its niches. Also, it is important for’ survival of both, the individual and the species.

Differentiate between the following

Question 1.
Habitat and Niche
Answer:
Differences between habitat and niche are as follows

Habitat	Niche
A place or part of an ecosystem, occupied by a particular organism.	A functiohal description of the role, a species plays in a community.
It can have number of niches.	It does not have any components.
A variety of environmental variables are present in a habitat.	Every niche has its own specific environment.

Question 2.
Mutualism and Parasitism
Answer:
Differences between mutualism and parasitism are as follows

Mutualism	Parasitism
It type of interaction in which both the interacting species gets benefits.	The mode of interaction in two species in which one (parasites) is dependent on another for benefits there by damaging the other one (host).
Mycorrhiza show mutual association between fungi and roots of higher plants.	Human liver-fluke depends on two intermediate hosts to complete its life cycle.

Question 3.
Hydrophytes and Xerophytes
Answer:
Differences between hydrophytes and xerophytes are as follows

Hydorphytes	Xerophytes
The plants which are adapted to live in abundance of water are called hydrophytes.	The plants which are adapted to live in condition of water scarcity and dry habitat are called xerophytes.
Root are poorly developed.	Roots are very well- developed.
Leaves are well-developed.	Leaves are modified in various structure.
Stomata are present abundantly.	Sunken stomata are present.
e.g. Hydrilla, Pistia.	e.g. Opuntia, Asparagus, etc.

Question 4.
Birth rate and Death rate
Answer:
Differences between birth rate and death rate are as follows

Birth rate	Death rate
It is the number of birth of new individuals per unit of population per unit time.	It is the number of loss of individuals per unit of population per unit time.
It increases the size of population.	It decreases the size of population.

Question 5.
Fertility and Fecundity
Answer:
Differences between fertility and fecundity are as follows

Fertility	Fecundity
Fertility is the natural ability to reproduce and is defined as the offspring per couple.	Fecundity is the actual reproductive rate of an organism or population measured by number of gametes, (seed sets or asexual propagules).

Question 6.
Logarithmic and Exponential growth
Answer:
Differences between logarithmic and exponential growth are as follows

Logarithmic growth	Exponential growth
Logistic or Logarithmic occurs rapidly and then slow down.	The kind of growth which is slow initially but, it increases as the population growth takes place.
It considers factors like competition and limited resources.	It requires specific ideal conditions to occur.
It occurs when the resources are limited.	It occurs when the resources are abundant.
It has four phases-lag, log, decelearatlon and steady.	It has two phases-lage and log.
It is more common, in human, etc.	It occurs in algal bloom, etc.

Long Answer Type Questions

Question 1.
Explain, what is population? Describe the different characteristics of population.
Answer:
The term ‘population’ can be defined as a group or assemblage of organisms of the same species living in a particular area at a given time.
For example, the lion population of the Gir forest or the peacock population of India, etc.

Population Interactions:
In nature, living organisms such as animals, plants and microbes, cannot live in isolation and therefore, interact in various ways to form a biological community. Interspecific interactions occur between the populations of two different species living together within a community.

These interactions could be beneficial (+), detrimental (-) or neutral (0), as shown in table below
Population Interactions and their Effects

Name of interaction	Effect on species-A	Effect on species-B
Mutualism	+	+
Competition	–	–
Predation	+	–
Parasitism	+	–
Commensalism	+	0
Ammensalism	–	0

Mutualism:
It is an interaction that confers benefits to both the interacting species. Some examples of mutualism are
1. Lichens represent an intimate mutualistic relationship between a fungus (mycobiont) and photosynthesising algae (phycobiont) or cyanobacteria. Here, the fungus helps in the absorption of nutrients and provides protection, while algae prepares the food.

2. Mycorrhiza show dose mutual association between fungi and the roots of higher plants. Fungi help the plant in absorption of nutrients, while the plant provides food for the fungus, e.g. many members of genus -Glomus.

3. Plants need help from animals for pollination and dispersal of seeds. In return, plants provide nectar, pollens and fruits to them.

4. Co-evolution to safeguard the mutually beneficial system, plant-animal interactions involve co-evolution of the mutualists, i.e. the evolution of the flower and its pollinator species are tightly linked with one another, e.g.

(i) Fig and its partner wasp species, the female wasp uses the fruit not only as an oviposition (egg-laying) site, but uses the developing seeds from the fruit for nourishing its larvae. In return, the wasp pollinates the fig inflorescence, while searching for suitable egg-laying sites.

(ii) Mediterranean orchid Ophrys employs ‘sexual deceit’ to get pollinated by a species of bee. One petal of its flower bears an uncanny resemblance to the female of the bee in size, colour and markings. The male bee is attracted to what it perceives as a female and ‘pseudocopulates’ with the flower. During this process, pollen are dusted from the flower onto the male bee. When the same bee pseudocopulates with another flower, it transfers pollen to it and thus pollinates the flower.

Competition:
It is generally believed to occur when closely related the two individuals of species compete for the same resources that are limiting. This can happen between the members of the same species, i.e., intraspecific or different species, i.e. interspecific. These are as follows

(i) Intraspecific competition occur for the resources which are short in supply such as food, space or mate. There are of two types

Content competition Where each organism claims a part of the resource, but due to competition, some are successful to get, but some fail.
Scramble competition In this case, the resource gets divided to many other smaller parts to which all have access. Individual organism scramble for resources. Each individual succeeds to get some of the resource available to survive.

(ii) Interspecific competition It occurs between members of different species, e.g. competition is likely to have two outcomes. These are as follows
1. Competitive exclusion According to Gause’s competitive exclusion principle two closely related species competing for same resources cannot co-exist indefinitely and the competitively inferior species will be eliminated eventually two species of beetles (Tribolium castaneum and T. confusum) feed on stored flour, one species would survive and other will die.

2. Co-existence Species facing competition might evolve a mechanism to live in the same niche by changing the feeding time or foraging pattern. This is called resource partitioning.

Question 2.
What do you understand by population? Explain the different attributes of the population.
Answer:
The term ‘population’ can be defined as a group or assemblage of organisms of the same species living in a particular area at a given time.
For example, the lion population of the Gir forest or the peacock population of India, etc.

Population Attributes:
Population is a unit of ecosystem through which the energy flows and nutrients get cylced which helps in maintaining its stability. A population has some features such as birth rate, death rate, growth form, age structure, density, etc. which are discussed below

1. Growth
When a few organisms are introduced to a particular unoccupied area, the population show growth (increase in size) in sigmoid or ‘S’-shaped logistic fashion.

The few organisms are introduced to a particular unoccupied area, the growth of population initially is slow (positive acceleration phase). Then suddenly there is sharp increase and growth becomes vary rapid (logarithmic phase). At last stage it finally slow and down because of the increased environmental resistance (negative acceleration phase). It is dipicted in the given [fig. 14.19(a)], The increase of population size does not occure beyond a certain saturation limit. This is known as carrying capacity .
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 1
The sigmoid and exponential growth curves

Another kind of population curve in J-shaped this the density of organism increase rapidly, but stops suddenly due to environmental resistance. It is called exponential growth curve.

(i) Growth Rate:
The growth rate of a population can be determined by the following formula
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 2

Population size for a given species is not static parameter, but it is ever changing based on different factors including food availability, predation pressure and weather diversity. The population thickness changes because of the following four changes

Natality It refers to the number of “births during a given period in the population that are added to the initial density.
Mortality It is the number of deaths in the population during a given period.

Factors influencing population density

2. Birth Rate and Death Rate:
The increased and decreased rate of population depends on birth and death natality is related new homes, i.e. the reproduction capacity of individuals. It is related with two aspects of reproduction.

Thus, natality or birth rate of a population can be expressed as
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 4
Where, b = Natality per unit time, d – Changing value of the entity, N = Initial number of individuals in population, Nn – Number of new individuals added and t = Unit time.

Similarly, the death rate or mortality rate is the death or loss of individuals from the population in unit time and can be expressed as
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 5
The death rate has a relation with the natality because of over crowding, predation and spread of disease.

3. Sex Ratio:
It represents the ratio of organisms of different sexes of the population. In animals, sex is either male or female which creates difference in the characteristic of the population.

4. Age Distribution:
A population at a given time is composed of individuals of different age groups such as pre-reproductive, reproductive and post-reproductive. The population age distribution is related to the growth rate of the population and this can be used to calculate whether the population is expanding or contracting.

Ordinarily, a rapidly expanding population would have a large proportion of young individuals, a stationary population with even distribution of age groups and declining population contain a large proportion of old individuals.

These age groups of the population can be portrayed through the graphical age pyramid representations.In human population, the age pyramids generally express age distribution of males and females in a combined diagram. The shapes of the pyramids reflect the growth status of the population.

The pyramids can be of three difference types as follows
(i) Expanding (Triangular) This is a type of a growing population representation is like a triangle.
The population carries a high proportion of pre-reproductive individuals followed by reproductive individuals and post-reproductive individuals. Because of the very large number of pre-reproductive individuals, more and more of them enter reproductive phases and rapidily increases the size of the population.

(ii) Stable (Bell-shaped) This type of pyramid will represent a stationary or stable population having an equal number of young and middle aged class of individiuals.

(iii) Declining (Urn-shaped) This group has a small number of pre-reproductive individuals followed by a large number of reproductive individuals. As, there is less number of individuals in pre-reproductive groups.
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 6

5. Population Density
This refers to the size of population to a unit space at a particular time. This can be measured is several ways an mentioned below

Abundance (absolute number in population).
Numerical density (number individuals per unit area).
Biomass density (biomass per unit area).

The density of population can be expressed in the following manner
(a) Crude density This is the density of a species population with reference is the total area. It varies according to the season, weather, food supply rate of reproduction, etc.
(b) Ecological density This is the density of a species with reference to the actual area of habitat available to the species.

Question 3.
Explain, how different organisms interact in a population emphasising on the possibilities of various relationships.
Answer:
The term ‘population’ can be defined as a group or assemblage of organisms of the same species living in a particular area at a given time.
For example, the lion population of the Gir forest or the peacock population of India, etc.

Predation
It is an interspecific interaction, where an animal called predator kills and consumes the other weaker animal called prey. This is a biological control method. It is the nature’s way of transferring energy to higher trophic levels, which is fixed by plants at the first trophic level, e.g. tiger (predator) and deer (prey).

Important roles of predators are as follows
1. In the absence of predators, prey species could achieve very high population densities and cause instability. So, besides acting as ‘conduits’ for energy transfer across trophic levels, predators play very important role in providing population stability.

2. They help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species, e.g. predator starfish Pisaster in the rocky intertidal communities of American Pacific Coast. In a field experiment, when all the starfish were removed from the area, more than 10 species of invertebrates became extinct within a year, because of interspecific competition.

3. When certain exotic species are introduced into a geographical area, they become invasive and start spreading fast because the invaded land does not have natural predators, e.g. prickly pear cactus introduced in Australia in early 1920s was brought under control by introducing its predator (i.e. a moth) in the country.

If a predator is too efficient and over exploits its prey, then the prey might become extinct.
Following it, the predator will also become extinct because of the lack of food. This is why predators in nature are prudent.
Prey species have evolved various defence mechanisms to lessen the impact of predation. These are as follows

In Animals:

Camouflage Some species of insects and frogs are cryptically coloured (camouflaged) to avoid being detected easily by the predator. Some are poisonous and therefore, avoided by the predators.
Chemical emission Monarch butterfly is highly distasteful to its predators (birds) because of a special chemical present in its body. The butterfly acquires this chemical during its caterpillar stage by feeding on a poisonous weed.
Mimicry It refers to the resemblance of an organism to their natural surroundings which hides them from eyes of predators.

In Plants
Nearly 25% of all insects are known to be phytophagous (feeding on plant sap and other parts of plants) apart from other herbivores. So, plants have evolved various defences against them, e.g., thorns of Acacia and cactus are the most common morphological means of defence.

Some plants produce highly poisonous chemicals like cardiac glycosides, e.g., weed Calotropis that makes the herbivore sick, etc.
Chemicals like nicotine, caffeine, quinine, strychnine, opium, etc., are actually defence mechanisms against grazers and browsers.

Parasitism:
It is the mode of interaction between two species in which one species (parasite) depends on the other species (host) for food and shelter and damages the host. In this process, one organism is benefitted (parasite), while the other is being harmed (host).

(i) Adaptation methods of a parasite are
Parasite is host-specific in a way that both host and parasite tend to co-evolve. According to its lifestyle, a parasite, evolved special adaptations as

Loss of unnecessary sense organs.
The presence of adhesive organs or suckers for clinging on to host.
Loss of digestive system.
High reproductive capacity.

(ii) The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate parasitisation of its primary host,, e.g.

Human liver fluke (a trematode parasite) depends on two intermediate hosts (a snail and a fish) to complete its life cycle.
Malarial parasite (Plasmodium) needs a vector (mosquito) to spread to other hosts.

(iii) Majority of parasites harm the host. The harm is done in the following ways

They reduce the survival, growth and reproductive ability of the host.
They reduce its population density.
They might render the host more vulnerable to predation by making it physically weak.

Types of Parasites
Parasites are broadly divided into following main types

Ectoparasites depend on the external surface of the host organism for food and shelter, e.g., lice on humans, ticks on dogs, copepods in marine fishes and Cuscuta, a parasitic plant that grows on hedge plants.
Endoparasites live inside the host’s body at different sites like liver, kidney, lungs, etc., for food and shelter, e.g. tapeworm, liver fluke, Plasmodium, etc. The life cycles of endoparasites are more complex because of their extreme specialisation.
Brood parasitism is an example of parasitism in which one organism (parasite) lays its eggs in the nest of another organism (host) for the later to incubate them.

The eggs of parasitic birds have evolved to resemble the host’s egg to reduce the chances of host bird from detecting and ejecting the parasitic eggs from nest, e.g., cuckoo (koel, parasite) and crow (host) during breeding season (spring to summer).

Effects of Parasites on Host
There always exist some kind of host parasite relationship which has following characteristics parasites do not kill the host immediately, but they make the host to suffer, they damage their body and in extreme case they may cause their death. These reduce the growth of the host and also afffect their reproductive potential. They also reduce the size of the population of host.

Question 4.
What is habitat? Describe the different types of abiotic factors present in the habitat.
Answer:
Habitat:
Environment is termed as sum total of all external conditions which influence the organisms in term of survival and reproduction. Habitat is a natural abode or locality where a plant/ animal grow, based on the environment, the differences in the vegetation and species of different places are observed.

Abiotic Factors:
These include climatic, edaphic and topographic factors. Climatic factors are light, temperature, precipitation, humidity, wind. Edaphic factors are factors related to soil whereas topographic factors are physical factors related to slope, altitude and others concerned with earth surface. Some of the major abiotic factors are discussed below
1. Light
Sunlight is the primary source of light. It plays an important role in almost all ecosystems. The entire food chain starts with the organisms that are photosynthetic (producers).

So without sunlight, all life excluding some microbes would perish, not just the plants. The total amount of light that falls on the earth varies according to the season, latitude, altitude and conditions of the atmosphere. The significance of light lies in the fact that all autotrophs depend upon light as a source of energy for preparing their food by photosynthesis and release oxygen during the process.

Therefore, it is an important factor for life to exist on earth. Small herbs and shrubs growing in forests are adapted to photosynthesis under very low light intensities, because they are overshadowed by the tall, canopied trees. Most plants depend on sunlight to meet their photoperiodic requirement for flowering also.

The spectral quality of solar radiation as shown in figure is also important for life. The UV component of light is harmful for many organisms. Different components of the visible spectrum are available for marine plants living at different depths of the ocean.
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 1
This is why different types of algae, i.e., green, brown and red algae occur at different depths in sea in the upper, middle and deep layers of water respectively.
Plants which grow in bright light are called sun plants or heliophytes while plants growing in shade or low intensity light are called sciophytes.
Depending upon the availability of light aquatic body is divided into the following zones

Littoral zone ft adjoins the shore and extends to the point water body when producers (plants) show the light compensation level. The point indicate the rate of photosynthesis equalising with the rate of respiration.
Limnetic zone It is the major open area of waterbody next to the littoral zone. The O₂ availability to the organisms living in this area is from the photosynthetic activity of phytoplanktons and in the atmosphere immediately over the water or lake’s surface.
In the limnetic zone, the region which gets the maximum light above the light compensation point is called euphotic zone.
The region where light is received less and diffused and is below the light compensation point is disphotic zone.
Profundal zone This is the bottom area of the pond, where respiration is greater than production.
Benthic zone It is the zone of darkness. No light, penetrate in the deeper layers of waterbody. The organism living here in this zone have poorly developed eye sight. The producers are mainly chemosynthetic bacteria.

Zonation in deep lake showing gradient of light and oxygen

2. Temperature
It is the most ecologically significant environmental factor. It varies seasonally on land and decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from sub-zero levels in polar areas and high altitudes to > 50°C in tropical deserts in summer. There are also certain unique habitats such as thermal springs, deep sea hydrothermal vents where the average temperature exceeds 100°C.

Physiological functions as well as geographical distribution of plants and animals are governed by the temperature conditions and their thermal tolerance. Organisms which can tolerate and thrive in a wide range of temperatures are called eurythermal, e.g., most mammals and birds while organisms which can tolerate a narrow range of temperatures are called stenothermal, e.g., polar bear, amphibians.

3. Precipitation
Rainfall and hail storm are two major forms of precipitation. The only available form of water to the plant is the soil water. So, precipitation is indirect form of water which affect the plant life and water content of ‘ the soil. The vegetation of an area is directly or indirectly affected by the precipitation received by that area.

4. Soil
The nature and properties of soil in different places vary significantly. It is dependent mainly on the following factors

Climate
Weathering process
Whether soil is transported or sedimentary
Soil development process

Water holding capacity and percolation of the soil is determined by its various characteristics, such as soil composition, soil particle size and aggregation of soil particles.

These characteristics of soil along with its pH, mineral composition, topography, etc., determine the type of plants that can grow in a particular habitat and the type of animals that can feed on them. In aquatic environment also, the bottom sediments and its characteristics determine the type of benthic animals that can live there. Thus, the key abiotic factors affecting the organisms.

Besides these prominent abiotic factors, biotic factors are also forming a habitat and are the part of ecological environment.

Question 5.
What are the various adaptations different plants adapt for their survival in different habitats?
Answer:
Adaptations in Hydrophytes
Adaptations in hydrophytes can be discussed under three headings, i.e. morphological, anatomical and physiological.
1. Morphological Adaptations
Hydrophytes show various kinds of structural adaptations in their roots, stems and leaves.
(i) Root

Roots may be entirely absent, e.g. Woljfia, Salvinia or poorly developed, e.g. Hydrilla.
Roots are well-developed with distinct root caps, e.g. Ranunculus (emergent hydrophytes), aerenchymapresent.
In Eichhornia root caps are replaced by root pockets.
Some plants, i.e. Jussiaea have two types of roots, one is normal type and other is spongy and negatively geo trophic.

(ii) Stem

In Hydrilla, Potamogeton, the stems are slender spongy flexible.
Horizontal stems are found in floating hydrophytes like Azolla, Pistia or Eichhornia.
In rooted hydrophytes like Sagittaria, Cyperus, Scirpus, the stem is rhizome or stolon.

Stolon stems in marshy plants

(iii) Petioles
Some hydrophytes show special features in the petioles.

Petioles in submerged plants, with free-floating leaves like Nymphaea and Nelumbium, are long, slender and spongy.
In the free-floating hydrophyte Eichhornia, stems are long slender and spongy.
In the free-floating hydrophyte Eichhornia, the petiole is swollen have big air spaces in side tissues and helps in floating.

TS of petiole of Eichhornia

(iv) Leaves
The structural details of hydrophytes show number of variations, which can be summerised as follows

In Vallisneria the leaves are long and narrow.
These are finely dissected in Utricularia, Myriophyllum and Ceratophyllum. This helps aquatic plants to provide little resistance against water.
The free-floating hydrophytes have wax coating on than, these are shiny and smooth. Wax coating present dessication of leaves in water scarce condition.
In Nelumbium and Nymphaea the leaves remain in touch with water surface and upper layer is exposed to the air.

The amphibions hydrophytes exhibit the phenomenon of heterophylly (two types of leaves). The submerged leaves are dissected to go with’water currents while above water are broad, e.g. Sagittaria, Ranunculus, Limnophylla heterophylla.

2. Anatomical Adaptations
Hydrophytes show the following anatomical features
(i) Reduction in Protecting Structures

Cuticle is absent in submerged portion.
Epidermis has chloroplast, used as photosynthesising organ.
Hypodermis is poorly developed.

(ii) Reduction of Mechanical Tissue

Sclerenchyma is absent or poorly developed in submerged portions.
Asterosclereids is present that provide mechanical support in case sclerenchyma is absent.
Sclerenchyma present only in aerial tissues.

(iii) Reduction of Conducting Tissue

Vascular bundles are reduced to few or even one, e.g Hydrilla.
Xylem cells are very few.
Phloem is usually poorly developed, but in some cases it is well-developed.
Secondary vascular tissue is totally absent.

(iv) Increase in Aeration

Stomata are totally absent or poorly developed in submerged parts.
If present, stomata are confined to upper surface leaves.
In amphibious plants, stomata are scattered on the aerial portions.
Roots, stems and leaves of most hydrophytes have parenchymatous tissue with air chambers. These chambers store gases like CO₂ and O₂ and help in respiration and photosynthesis. These are hence, called aerenchyma. Besides, the air chambers help in buoyancy and provide mechanical support.

TS of root of Typha

3. Physiological Adaptations
Besides their adaptations in the morphological and anatomical characters, hydrophytes also show physiological adaptations.

Osmotic concentrations of cell sap is low.
Photosynthetic and respiratory gases are retained in air chambers for further use.
No transpiration occurs in submerged plants.
In hydrophytes, mostly vegetative reproduction.

Xerophytes:
These are the plants which are adapted to drier regions and have high rate of transpiration than absorption of water.

Types of Xerophytes
Xeric habitats are of two types
(i) Physically dry habitats are those in which water cannot be retained (deserts, rock surface).
(ii) Physiologically dry habitats have plants of water, but the water is not available to the plant.

Based on their adaptation to water scarcity or drought conditions, xerophytes are of three types

Drought resistant plants are such that they can survive in extreme conditions, drought enduring plants can tolerate drought though they may hot have adaptation.
Drought enduring plants these do not have distinct adaptation.
Drought escaping plants these are short lived plants, complete the life cycle before the arrival of dry condition, e.g. Artemisia, Astragalus.

Succulents xerophytes

Based on their capacity to store water, xerophytes are classified as succulents and non-succulents. Succulents like Opuntia, have their organs swollen due to accumulation of water, whereas non-succulents are considered as true xerophytes.
CHSE Odisha Class 12 Biology Solutions Chapter 14 Organisms and Environment 12

Adaptation in Xerophytes:
These show varied adaptions in the morphology, anatomy and physiology which are as follows
1. Morphological Adaptations
Xerophytes exhibit a number of special features in their body organs as given below

(i) Roots

Roots are very extensive, long tap roots, with branching spread over wide areas.
Root hairs and root caps are very well-developed.

(ii) Stem

Stems are stunted, woody, dry, hard and covered with thick waxy cuticle.
In Opuntia stem becomes green and fleshy (phylloclade).
On stems and leaves, there are hairs and waxy coatings.
Succulents have their stem modified into leaf-like structures called cladodes as in Asparagus.

(iii) Leaves
The leaves of xerophytes are reduced to spines to various structures. This helps plants to reduce rate of respiration. The following types of leaf conditions are seen

Microphyllous when leaves are scaly (Casuarina) and needle-like Pinus.
Trichophyllous when leaves are covered with hairs (.Nerium, Calotropis).
Macrophyllous when leaves are soft and flesh (Begonia).
Sclerophyllous plants showing leaves which are tough and hard.
Cadueous when leaves fall early, i.e. plants with no leaves.
Rolling leaves in ammophilis stomata are directed in words.

Anatomical Adaptations:
These adaptations can be conveniently discussed under the headings, i.e. epidermis, hypodermis and vascular tissue.
(i) Epidermis

Some xerophytes have multiple epidermis, e.g. Nerium.
It has thick cuticle and deposition of waxes, resins, etc.
Epidermal hairs are present in grooves.
Some leaves have bulliform cells that help in rolling.
The stomata are present in sunken pits to reduce transpiration rate.
Stomatal frequency is very low in xerophytes.

(ii) Hypodermis
It is thick and well-developed and is made up of parenchymatous cells.

(iii) Ground Tissue

In stems, there is abundant mechanical tissue in the form of sclerenchyma, e.g. Casuarina.
Since, leaves are reduced, the stems usually have chlorenchyma.
In succulent plants, cortex is filled with water, mucilage, latex, etc.
In plants that have leaves, palisade parenchyma is well-developed.
In Pinus, mesophyll cells are modified.
Intercellular spaces are greatly reduced.

(iv) Conducting Tissue
Vascular tissue (xylem and phloem) .is very well-developed in xerophytes.

3. Physiological Adaptations

Osmotic concentration of the cell sap is very high.
Succulents have high pentosan (chemicals derived from polysaccharides) resulting in accumulation of water.

CHSE Odisha Class 12 Biology Solutions Chapter 13 Applications of Biotechnology

July 24, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 13 Applications of Biotechnology Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 13 Question Answer Applications of Biotechnology

Applications of Biotechnology Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple Choice Questions

Question 1.
Golden rice is produced by rice plant having a transgene encoding an enzyme in biosynthetic pathway of
(a) P-carotene
(b) luciferin
(c) glyphosate
(d) Bt protein
Answer:
(a) P-carotene

Question 2.
Fruit ripening is delayed by preventing the expression of the enzyme
(a) luciferase
(b) polygalacturonase
(c) nitrogenase
(d) adenosine deaminase
Answer:
(b) polygalacturonase

Question 3.
Humulin is manufactured by
(a) Pfizer
(b) Hoechst
(c) Eli Lilly
(d) Aventis
Answer:
(c) Eli Lilly

Question 4.
Genetic correction of inflicted cells is made in vitro and then reimplanted into its natural environment. This therapy is known as
(a) ex vivo gene therapy
(b) in vivo therapy
(c) in vitro therapy
(d) in toto therapy
Answer:
(a) ex vivo gene therapy

Question 5.
The first genetic disorder treated by gene replacement therapy is
(a) Familial Hypercholesterolemia (FH)
(b) Cystic Fibrosis (CF)
(c) Duchenne Muscular Dystrophy (DMD)
(d) Severe Combined Immunodeficiency (SCID)
Answer:
(d) Severe Combined Immunodeficiency (SCID)

Question 6.
Patent is not granted for
(a) a novel invention
(b) an invention having an industrial application
(c) a discovery made by previously existing knowledge
(d) an invention having an inventive step
Answer:
(c) a discovery made by previously existing knowledge

Question 7.
Which of the following is not related to biosafety?
(a) Convention on Biological Diversity
(b) Cartagena Protocol
(c) World Trade Organisation
(d) UNICEF
Answer:
(d) UNICEF

Question 8.
Which of the following patent cases, India is not directly or indirectly connected with?
(a) Soybean patent case
(b) Neem patent case
(b) Turmeric patent case
(d) Chakraborty patent case
Answer:
(a) Soybean patent case

Question 9.
The supermouse is a genetically modified animal with
(a) insulin transgene
(b) lipid biosynthesis transgene
(c) growth hormone transgene
(d) steroid hormone transgene
Answer:
(c) growth hormone transgene

Question 10.
Which is the nodal centre for Indian biosafety network?
(a) Department of Biotechnology
(b) Department of Science and Technology
(c) Indian Agricultural Research Institute
(d) Department of Forest and Environment
Answer:
(a) Department of Biotechnology

Fill in the blanks

Question 1.
The mass of undifferentiated plant cells in a plant tissue culture media is known as ……………..
Answer:
Callus

Question 2.
Herbicide resistant plants are generated by plant tissue culture technique by transferring …………… gene of a bacterium into a plant protoplast.
Answer:
glyphosate

Question 3.
A bacterium species of ……………. genus is genetically engineered to prevent frost formation in plants.
Answer:.
Pseudomonas

Question 4.
A bioluminescent plant is generated by transferring ………….. gene of a firefly into plant protoplasts.
Answer:
luciferase

Question 5.
Golden rice producing plant is a transgenic plant, whose cells have a transgene encoding …………
Answer:
ß-carotene

Question 6.
Delayed ripening in tomato is due to the inhibition of expression of an enzyme ……………..
Answer:
polygalacturonase

Question 7.
The first recombinant human vaccine produced and marketed is …………. vaccine.
Answer:
hepatitis-B

Question 8.
Recombinant insulin in the trade name of Humulin is manufactured by …………….
Answer:
Eli Lilly Corporation

Question 9.
Monoclonal antibody is synthesised and secreted by a cell known as ……….
Answer:
B-lymphocytes

Question 10.
Severe Combined Immunodeficiency (SCID) is expressed due to the absence of an enzyme, …………… .
Answer:
adenosine deaminase

Question 11.
A forensic analysis of DNA for establishing the identity of a person is known as …………….. .
Answer:
DNA fingerprinting

Question 12.
An immunological technique, applied to detect the presence of very minute quantity of antigen in the serum is known as …………. .
Answer:
ELISA

Question 13.
A biopesticide, known as Bt protein is expressed by a bacterial species, ………… .
Answer:
Bacillus thuringiensis

Question 14.
A legal right, privilege and authority granted to a person for a limited period for an invention is known as …………. .
Answer:
patent

Question 15.
The use of novel biological resource of a sovereign country without its due permission is known as …………….. .
Answer:
biopiracy

Express in one or two word(s)

Question 1.
The tomato plant variety that bears tomatoes exhibiting delayed ripening.
Answer:
Flaw savr

Question 2.
The somatic hybrid cell, which produces monoclonal antibodies.
Answer:
Hybridoma

Question 3.
Genetically engineered rice, rich in vitamin-A.
Answer:
Golden rice

Question 4.
An insecticidal protein, produced by Bacillus thuringiensis.
Answer:
Cry protein

Question 5.
A broad spectrum herbicide that is used world over.
Answer:
Glyphosate

Question 6.
The biotech company, which commercially manufactured the first recombinant human insulin.
Answer:
Genentech

Question 7.
The first genetic disorder that was treated by gene therapy.
Answer:
SCID

Question 8.
The gene transfer into the mammalian fertilised egg with a micropipette.
Answer:
Microinjection

Question 9.
The gene transfer method practiced by passing intermittent pulses of electric current through the medium containing plant protoplasts.
Answer:
Electroporation

Question 10.
The corn was genetically engineered by transferring Bt protein gene into plant protoplasts. The brand was marketed and later was withdrawn due to safety reasons.
Answer:
Star Link corn

Question 11.
The biosafety protocol that was drafted in 1995 and adopted in 2000.
Answer:
Cartagena Protocol

Short Answer Type Questions

Answer each of the following within 50 words

Question 1.
What is golden rice?
Answer:
Golden rice is a transgenic variety of rice with an elevated level of ß-carotene (provitamin-A), a precursor of vitamin-A. The genes encoding the enzymes of the ß-carotene biosynthetic pathway are introduced into rice plant cells in culture. The transgenic rice plants generated produce rice with ß-carotene.

Question 2.
What is Flavr Savr tomato?
Ans.
Fruit ripening in tomato and other fruits and vegetables are delayed by manipulating a gene, involved in softening and ripening. A variety of tomato plant has been successfully engineered, which bears tomatoes, known as Flavr Savr tomatoes. This variety exhibits delayed ripening.

Question 3.
What does the recombinant hepatitis-B vaccine contain?
Answer:
Hepatitis-B vaccine contains surface antigen proteins (HBs Ag) extracted from Hepatitis-B Virus (HBV).

Question 4.
What do you understand by ex vivo gene therapy?
Answer:
Ex vivo gene therapy The affected cells are removed from the body and transformed by the remedial gene in vitro. The transformed cells are grown in a cell culture medium to a sufficient number and then returned to the body by transfusion or transplantation.

Question 5.
What do you mean by a biopesticide? Give an example.
Answer:
Biopesticides are the type of pesticides produced from an organism. They are equally potent but do not inflict a damage on the environment, e.g. a species of bacteria with insecticidal properties is Bacillus thuringiensis. It produces insecticidal cry protein or Bt protein.

Question 6.
What is a supermouse?
Answer:
R L Brinster and R Palmiter (1982) successfully created the first transgenic mouse by transferring the rat growth hormone gene into the fertilised mouse egg by microinjection. This act was carried out in vitro.

Following the transfer, the fertilised egg was implanted into the uterus of a pseudopregnant mouse.
The mouse gave birth to mice that were relatively larger in size, possibly due to an increased synthesis of growth hormone directed by the rat growth homone transgene. This mouse was called supermouse because of its abnormal growth.

Question 7.
Explain biopiracy.
Answer:
Illegal transfer of biological resources has been termed as biopiracy. It describes a practice, in which indigenous knowedge and processes used by indigenous people of a region is used by others for profit without permission from and with little or no compensation or recognition to the indigenous people themselves. This is an illegal practice and enforceable in the court of law.

Question 8.
Ennumerate and explain in brief two biosafety issues, biotechnology is confronted with.
Answer:
Biosafety in a broad sense, refers to the prevention of loss of biological integrity of biological processes and products, harvested by using living organisms. For example, recombinant insulin was manufactured in a complex biological process putting in thought, knowledge, skill and execution method of the inventor. Secondly, a lot of energy and money was spent in the successful execution of the process. Therefore, the right of the inventor needs to be protected by law considering it as a property.

On the other hand, insulin that is manufactured a prescribed trial process to prove that it is suitable for human use. Another potential hazard was the release of Genetically Modified Organisms (GMOs) into the wild. There was a threat that it might sexually reproduce with organisms of its own species and exchange genes, consequently changing the structure of the gene pool.
This might have produced an adverse effect on organic evolution. Thus, normal biological diversity might be destabilised.

Question 9.
Describe the evolution of Indian Patent Act.
Answer:
India enacted the Patent Act in 1970. The Act has undergone amendments in 1999, 2002, 2005 and 2006. The headquarter for the same is in KolKata, West Bengal. The nodal centre for Indian biosafety network is the Department of Biotechnology, Government of India.

Question 10.
Describe the neem patent case.
Answer:
Neem Patent Case:
The multinational agribusiness company, WR Grace of New York and United States Department of Agriculture, Washington DC filed, for a European patent for the fungicidal use of neems oil in the European Patent Office (EPO). It was stated that neem oil controlled fungal growth on plants.

The plea was accepted and a patent was granted. However, following the publication, Dr. Vandana Shiva of Research Foundation for Science and Technology and Natural Resource Policy, New Delhi and others filed a legal opposition to the grant of patent in the EPO.

Write brief notes on the following

Question 1.
Flerbicide resistant plants
Answer:
Herbicide resistant plants Herbicide resistant transgenic plants are generated by transferring bacterial herbicide resistant genes into plant cells grown in culture. Glyphosate is the most widely used broad-spectrum herbicide world over.
A glyphosate resistant gene from Petunia plant is transferred into isolated plant cell§ in culture and glyphosate resistant plants are generated.

Question 2.
Humulin
Answer:
Genentech is the first biotech company to manufacture recombinant human insulin in 1978 using bacteriophage vector and E. coli as the cloning and expression host cell. Later, this technology was licenced to Eli Lilly Corporation of USA.

The recombinant human insulin was termed as Humulin. It was approved as the first recombinant drug by the Food and Drug Administration (FDA), USA for human use. Since then, several companies all over the world have been manufacturing recombinant human insulin on a commercial basis.

Some noteworthy companies are Novo Nordisk of Denmark; Hoechst and Aventis of Germany and Pfizer of USA. Wokhardt Limited, a pharmaceutical company has been manufacturing human insulin in India under the trade name of Wosulin.

Question 3.
Recombinant vaccine
Answer:
Recombinant Vaccines
An antigcnic agent, which after being administered into an animal, generates an active acquired immune response is called as vaccines. The antigenic agent involved in vaccine production varies from vaccine to vaccine.

They generally belong to three classes-attenuated (inactivated) whole organisms isolated antigenic proteins such as coat proteins of viruses and inactivated touns. The latter two fall under the subunit vaccine class, wherein part of the organism possessing antigenic property is used in the vaccine production.

In these vaccines, a DNA insert encoding an antigen (like bacterial surface proteins) is introduced into a less virulanc host. These elicit an immune response expressing the antigens but do cause infection. The expressed antigens are isolated and puri&d and injectedinto the human hosts as a vaccine. It is called recombinant vaccine.

Question 4.
Gene therapy
Answer:
Gene therapy is a therapy or treatment of a gene, which has been mutated. It is a therapy to correct the damage. A genetic disorder is expressed, when a particular gene is mutated.

The mutant gene, as it is known, encodes a different polypeptide other than a normal. This polypeptide is the root cause of the expression of symptoms of a genetic disorder.
Attempts have been made to rectify or replace the mutant gens, so that they express normally. This replacement process is called gene therapy.

Question 5.
Biopesticide
Answer:
Bacillus thuringiensis is known to produce endotoxins or insecticidal crystalline protein or Cry protein or Bt protein.
Bt protein is hydrolysed by an alkali into 250 kD (kilodalton) units, known as protoxins. Each protoxin consists of two 130 kD polypeptides. The 130 kD polypeptide is digested into a 68 kD toxin polypeptide in an alkaline pH. When catepillars eat the leaves of crop plants, on which the bacterial spores are deposited, they ingest the spores.

The spores germinate in the alimentary canal, the bacteria grow in size and produce Bt protein. This protein is digested into 68kD toxin polypeptides in the intestine of the larva. The action of the poypeptide, eventually kills the larva. The alimentary canal of mammals, including human, produces an acid, which degrades the Bt protein. Thus, it is apparently harmless to human and other mammals. Since, this pesticide is produced from an organism, it has been identified as biopesticide.

Question 6.
Transgenic animals
Answer:
Transgenic animals are those which can grow faster, yield more milk, lay bigger eggs and so on. They are produced by combining traditional breeding with gene technology, which yield encouraging results. It involves selecting, isolating, purifying and transferring beneficial genes of one species to another to harvest a beneficial effect. These animals are the transfer of the beneficial gene (genes) developed. The gene that is transferred is known as a transgene. The transgene is transferred by using one of the several methods of gene transfer in practice. Microinjection is found to be most suitable for animal cells.

Question 7.
Patent
Or What is patent?
Answer:
Patent is an open letter granting legal right, privilege and authority by a sovereign state to a person or an institution for a limited period of time. It is given for an invention using scientific and technical knowledge. All sovereign countries have enacted their own Patent Acts to regulate the use of such properties.

An invention involves new knowledge, while a discovery is an application of the knowledge. For example, the double helical model proposed by Watson and Crick was a discovery and hence, does not qualify to be patented, while new forms of DNA, such as recombinant DNAs have been patented.

Question 8.
Biopiracy
Answer:
Biopiracy is theft or robbery or exploitation of biological and genetic resources indigenous to a country. These biological resources are often the main targets of enterprising businessmen because of their many uses in agriculture, healthcare and chemical industries. The process of biopiracy involves collection of samples of biological resources, which then undergo product development for their use on a commercial scale.

Biopiracy begins with biodiversity prospecting, which is exploration of wild plants and animals for commercially viable genetic and biochemical resources. Genetic resources are the genes found in plants and animals that are of actual or potential value to people.

Through the use of new biotechnologies, genes/germplasm from any plant or animal can be transferred to another. Such genetically engineered organisms (plants, animals and microorganisms) are being used for new industrial applications, pharmaceuticals, farming, cattle breeding and poultry farming.

CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology

July 24, 2025July 23, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 12 Question Answer Principles and Processes of Biotechnology

Principles and Processes of Biotechnology Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
The double helical structure of DNA was proposed by
(a) Jacob and Monod
(b) Sanger and Gilbert
(c) Watson and Crick
(d) Beadle and Tatum
Answer:
(c) Watson and Crick

Question 2.
Polymerase chain reaction was discovered by
(a) H G Khorana
(b) K Mullis
(c) R Holley
(d) M Nirenberg
Answer:
(b) K Mullis

Question 3.
Exonuclease is an enzyme that
(a) makes internal cuts in polynucleotide
(b) polymerises nucleotides
(c) joins two polynucleotide fragments
(d) removes nucleotides from the termini one after another
Answer:
(d) removes nucleotides from the termini one after another

Question 4.
DNA ligase is commonly known as
(a) molecular scissors
(b) molecular marker
(c) molecular glue
(d) molecular probe
Answer:
(c) molecular glue

Question 5.
During electrophoresis, DNA fragments move from
(a) anode to cathode
(b) remain static
(c) move randomly
(d) cathode to anode
Answer:
(d) cathode to anode

Question 6.
The blotting of protein molecules to a nylon membrane is known as
(a) Southern blotting
(b) Western blotting
(c) Northern blotting
(d) Eastern blotting
Answer:
(b) Western blotting

Question 7.
Detection of a desired DNA fragment by using radioactive emission is known as
(a) hybridisation
(b) denaturation
(c) autoradiography
(d) electrophoresis
Answer:
(c) autoradiography

Question 8.
Choose the incorrect statement.
(a) A plasmid is small, double-stranded circular DNA
(b) A plasmid contains an origin of replication
(c) A plasmid has several restriction sites
(d) A plasmid has telomeres
Answer:
(d) A plasmid has telomeres

Question 9.
A cosmid is a
(a) plasmid phage hybrid vector
(b) DNA bacteriophage vector
(c) expression vector
(d) viral vector
Answer:
(a) plasmid phage hybrid vector

Question 10.
The example of a plant cell compatible vector is
(a) fertility plasmid
(b) colicinogenic plasmid
(c) tumour inducing plasmid
(d) resistance plasmid
Answer:
(c) tumour inducing plasmid

Question 11.
Amplification of DNA by PCR uses a DNA polymerase called
(a) Taq DNA polymerase
(b) RNA polymerase
(c) DNA polymerase-III
(d) Reverse transcriptase
Answer:
(a) Taq DNA polymerase

Fill in the blanks

Question 1.
The phenomenon of fermentation was demonstrated by ……………
Answer:
Louis Pasteur

Question 2.
The word ‘biotechnology’ was coined by …………..
Answer:
Karl Ereky

Question 3.
Class II restriction endonucleases (enzymes) recognise specific nucleotide sequence in DNA called ……………
Answer:
palindromic sequence

Question 4.
Cohesive ends in the DNA fragments are generated by …………… cutting.
Answer:
staggered

Question 5.
The anionic detergent, used in polyacrylamide gel electrophoresis is known as
Answer:
Sodium Dodecyl Sulphate (SDS)

Question 6.
The transfer of separated protein molecules from the gel into a nylon membrane is known as ………….
Answer:
Western blotting

Question 7.
Detection of desired DNA fragment by the emission of ionising radiation is known as ……….
Answer:
autoradiography

Question 8.
The conjoint structure formed by the joining of the vector DNA and the target DNA fragment is known as …………..
Answer:
recombinant DNA

Question 9.
The uptake of the recombinant DNA by the bacterial host cell is known as ………….
Answer:
transformation

Question 10.
The delivery of a foreign DNA fragment into the fertilised egg with a micropipette is known as …………
Answer:
microinjection

Express in one or two word(s)

1. The technique of separation of DNA fragments based on their molecular weight and electrical charge.
Answer:
Electrophoresis

2. The restriction endonuclease isolated from Escherichia coli.
Answer:
Eco RI

3. The DNA digesting enzyme that removes nucleotides from the termini.
Answer:
Exonucleases

4. The enzyme that catalyses the synthesis of RNA on a DNA template.
Answer:
RNA polymerases

5. The enzyme that catalyses the replication of DNA.
Answer:
DNA polymerases

6. The enzyme that catalyses the synthesis of a complementary DNA strand on an RNA template.
Answer:
Reverse transcriptase

7. The fluorescent dye used in agarose gel electrophoresis.
Answer:
Ethidium bromide

8. Transfer of DNA fragments from the agarose gel to a nylon membrane.
Answer:
Southern blotting

9. Breaking of hydrogen bonds in a duplex so as to make it single-stranded.
Answer:
Denaturation

10. The DNA that helps carry the target DNA fragment to the host cell for cloning.
Answer:
Vector

11. The plasmid phage hybrid cloning vector.
Answer:
Cosmid

12. A plant cell, whose cellulose cell wall is digested.
Answer:
Protoplast

13. The plasmid present in Agrobacterium tumefaciens.
Answer:
Tumour inducing (Ti) plasmid

14. Transfer of a DNA fragment into a host cell in a medium by passing brief pulses of electric current through the medium.
Answer:
Electroporation

15. The instrument used in PCR amplification.
Answer:
Thermocycler

Match the words of group ‘A with those of group ‘B’ to make meaningful pairs

Question 1.

Group-A	Group-B
Restriction endonuclease	End modifying enzyme
DNA ligase	RNA dependent DNA polymerase
Exonuclease	Molecular scissors
Reverse transcriptase	Removes nucleotides from both ends
RNA polymerase	DNA dependent DNA synthesis
DNA polymerase	Molecular glue
Alkaline phosphatase	DNA dependent RNA synthesis

Answer:

Group-A	Group-B
Restriction endonuclease	Molecular scissors
DNA ligase	Molecular glue
Exonuclease	Removes nucleotides from both ends
Reverse transcriptase	RNA dependent DNA polymerase
RNA polymerase	DNA dependent RNA synthesis
DNA polymerase	DNA dependent DNA synthesis
Alkaline phosphatase	End modifying enzymes

Question 2.

Group-A	Group-B
Polyacrylamide	Agrobacterium tumefaciens
Southern blotting	Thermocycler
Plasmid	Protein electrophoresis
Agarose gel	Denaturation
Cos	Taq polymerase
Tumour inducing plasmid	Cloning vehicle
Recombinant DNA	Molecular marker
DNA coated tungsten particles	Nucleic acid electrophoresis
insertional inactivation	Chimeric DNA
Breaking of interchain hydrogen bonds	Particle gun
Equipment for PCR amplification	Screening of clones
Ampicillin resistance gene	Blotting of DNA
Thermophilus aquaticus	Cohesive site

Answer:

Group-A	Group-B
Polyacrylamide	Protein electrophoresis
Southern blotting	Nucleic acid electrophoresis
Plasmid	Cloning vehicle
Agarose gel	Blotting of DNA
Cos	Cohesive site
Tumour inducing plasmid	Agrobacterium tumetaciens
Recombinant DNA	Chimeric DNA
DNA coated tungsten particles	Particle gun
insertional inactivation	Screening of clones
Breaking of interchain hydrogen bonds	Denaturation
Equipment for PCR amplification	Thermocycler
Ampicillin resistance gene	Molecular marker
Thermophilus aquaticus	Taq polymerase

Short Answer Type Questions

Answer each of the following in 50 words

Question 1.
Define biotechnology.
Answer:
‘Biotechnology is an application of knowledge and technique of biochemistry, microbiology, genetics, immunology, tissue and cell culture, molecular biology, chemical engineering and computer science to living systems or parts therefore, for harvesting beneficial products and/or services for mankind.

Question 2.
Define gene cloning.
Answer:
The process of making a number of identical copies of a beneficial gene is known as gene cloning. Microorganisms, especially bacteria are chosen as host cells for this work, which provide a suitable environment for replication (amplification) of genes.

The gene is introduced into a bacterium by a process, known as transformation. For transformation, a gene is delivered into a bacterial host conjointly with a carrier, also DNA, known as a vector.

Question 3.
What is a restriction endonuclease (restriction enzyme)? Why is the word restriction used to designate these?
Answer:
These enzymes recognise specific recognition sequences on DNA and make the cut either within that sequence only or at a variable distance from that sequence. The site where they cleave or cut the DNA is called recognition site.
In rDNA technology, class-II REs are used.

Question 4.
Describe two types of cutting of DNA, executed by restriction endonucleases.
Answer:
Restriction Endonucleases
Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence.
Once, it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar phosphate backbones.

Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. Palindromes are group of letters that form the same words when read both forward and backward, e.g., ‘MALAYALAM’. Therefore, the palindrome in DNA is a base pair sequence that is the same when read forward or background, e.g., the following sequences read the same on the two strands in 5′ → 3′ direction as well as 3′ → 5′ direction.
5′- GAATTC – 3′
3′ – CTTAAG – 5′
Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands.

Question 5.
What is electrophoresis? How many types of electrophoresis you have studied?
Answer:
The cutting of DNA by restriction endonucleases results in the generation of DNA fragments which are then separated by a technique known as gel electrophoresis.
CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology 1
The DNA fragments are resolved (separate) according to their size through sieving effect provided by the gel when the potential difference is applied.
Two types of gels used in molecular separation are

Agarose Used for nucleic acids (RNA and DNA).
Polyacrylamide Used for proteins.

Question 6.
What is a palindrome? Give an example.
Answer:
Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. Palindromes are group of letters that form the same words when read both forward and backward, e.gy‘MALAYALAM’. Therefore, the palindrome in DNA is a base pair sequence that is the same when read forward or background, e.g., the following sequences read the same on the two strands in 5′ → 3′ direction as well as 3′ →5′ direction.
5′- GAATTC – 3′
3′ – CTTAAG – 5′

Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands.

Question 7.
What is a polymerase? How-many types of polymerases you have studied?
Answer:
Polymerases
These enzymes catalyse the process of copying the nucleic acid molecules. These are of following types
(i) RNA polymerase These are DNA dependent RNA polymerase.
(ii) DNA polymerase They copy DNA strand into another complementary strand through replication. These are also DNA dependent enzymes.
(iii) Reverse transcriptase They catalyse the synthesis of complementary DNA strand on RNA template. These are found in retroviruses and are RNA dependent DNA polymerase.
(iv) RNA polymerase They catalyse the process of strand copying of DNA into RNA through transcription.

Question 8.
Why is DNA ligase called molecular glue?
Answer:
DNA Ligases
These enzymes help to join or seal 3′-OH end of one nucleic acid fragment with the 5′-P end of another nucleic acid fragment by forming a phosphodiester bond. As they are able to stick DNA fragments together, they are known as molecular glue. The widely used ligase enzyme is T₄ DNA ligase. It is purified from E. coli cells that are infected by T₄ bacteriophages.

Question 9.
What is Southern blotting?
Answer:
Southern Blotting:
When the blotting is applied to DNA it is known as Southern blotting (named so after its discover EM Southern in 1975).
Following this, complementary DNA or RNA sequence (probe) labelled with 32 P (radioactive phosphorus) are, hybridised.
The probe binds its complementary target DNA sequence, by forming hydrogen bonds and a duplex is formed. This process is known as molecular hybridisation. The procedure that combines Southern blotting and molecular hybridisation is known as Southern blot hybridisation. After this, the target DNA sequence is identified using autoradiography.
CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology 2

Question 10.
Why is SDS used in polyacrylamide gel electrophoresis?
Answer:
A protein molecule contains many amino acids and all the amino acids do not have similar acid-base properties. Hence, a protein molecule cannot be conferred with uniform negative charges in a buffer solution.
It is therefore, treated with Sodium Dodecyl Sulphate (SDS), an anionic detergent that coats a protein molecule and confers negative charges uniformly.

Question 11.
What is autoradiography?
Answer:
Autoradiography:
The separated fragments in the gel are treated with an alkali to render the double-stranded fragments into single-stranded. This phenomenon is known as denaturation. These single-stranded fragments are then transferred onto a nitrocellulose filter paper or nylon membrane by a process known as blotting.

Question 12.
Enumerate the features of a suitable cloning plasmid.
Answer:
Plasmids:
These are small, autonomously replicating usually circular, extrachromosomal double-stranded DNA molecules that occur in many bacteria and some yeasts, but naturally occurring plasmids are not suitable for gene cloning. Therefore, they are genetically engineered so to make them compatible for cloning. These are then called as cloning vectors and, they possess the following additional properties other than these found in an ideal vector

They are non-conjugative.
They have relaxed replication and a high copy number.
They should be able to clone a gene in the range of 5-10Kb

The most commonly used cloning vector is pBR322 where p = plasmid; BR = Name of its engineers
[B = Boliver and R= Rodriguez]; 322 = Number of relevant workers who worked out this plasmid. pBR322 has the following features

• It is small, ds circular DNA molecule having ori.
• It has two antibiotic marker genes namely, ampicillin resistance gene amp^R and tetracyclin resistance gene (tet^R). In between these two genes, Eco RI restriction site is present.
• amp^R gene contains Pvu I and Pst I restriction sites.
• tet^R gene contains Bam HI and Sal I restriction sites.
• The target DNA and the vector DNA fragments should be compatible for a successful RDT process.
CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology 3

Question 13.
What is a recombinant DNA?
Answer:
The heterogeneous combination of two different DNAs in which the gene of interest is present is known as recombinant DNA or chimeric DNA and the technology is called recombinant DNA technology.

Question 14.
What is microinjection?
Answer:
Microinjection In this method, foreign DNA is directly injected into the nucleus of animal cell-or plant cell by using microneedles or micropip’ettes without any use of a vector DNA. It is used to v deliver a transgene or foreign DNA into the egg. Microinjection is especially used for transferring the foreign DNA in animal cells. The transgene is injected into the male pronuclei because it is larger and traceable with a dissecting microscope.

The male pronucleus is then fused with female pronucleus to produce zygote in vitro. In plant cells, the cellulose cell wall is first removed by enzymatic digestion before micro injection. This process is very tedious and involves a lot of precision.
CHSE Odisha Class 12 Biology Solutions Chapter 12 Principles and Processes of Biotechnology 3

Question 15.
Describe briefly electroporation.
Answer:
Electroporation It is the formation of temporary pores in the plasma membrane of host cells by using lysozyme or calcium chloride under high voltage of electric current. These pores are used for introduction of foreign DNA.
It can be used to transform plant protoplast, i.e. the plant cell with removed cell wall.

Question 16.
What is Polymerase Chain Reaction (PCR)?
Answer:
Polymerase Chain Reaction (PCR)
It is one of the important technique that serves the purpose of amplification of nucleic acid without using a host cell. PCR was discovered by Kary B Mullis in 1983.

Write brief notes on the following

Question 1.
Restriction endonuclease
Answer:
Restriction endonuclease These are specific enzymes, which recognise specific sequences called recognition sequences on DNA and make double-stranded cuts either within the recognition sequence or at a variable distance from the recognition sequence.

They act as scissors and therefore, often are referred to as molecular scissors. The point of cleavage is known as a restriction site. There will be as many restriction sites as the number of recognition sites. The REs that are used in the recombinant DNA technology fall under class-II. These make double-stranded symmetrical cuts within recognition sequences, generating cohesive or blunt ends.

Question 2.
DNA Ligases
Answer:
DNA Ligases
These enzymes help to join or seal 3-OH end of one nucleic acid fragment with the 5′-P end of another nucleic acid fragment by forming a phosphodiester bond. As they are able to stick DNA fragments together, they are known as molecular glue. The widely used ligase enzyme is T4 DNA ligase. It is purified from E. coli cells that are infected by T4 bacteriophages.

Question 3.
DNA polymerase
Answer:
DNA polymerase enzyme polymerises the DNA synthesis on DNA template or complementary DNA (cDNA). It was discovered by A. Kornberg and co-workers in E. coli in 1956 in the presence of a preformed DNA template, it produces a parallel strand in the presence of ATP.

Question 4.
Southern blotting
Answer:
When the blotting is applied to DNA it is known as Southern blotting (named so after its discover EM Southern in 1975).
Following this, complementary DNA or RNA sequence (probe) labelled with 32 P (radioactive phosphorus) are, hybridised.
The probe binds its complementary target DNA sequence, by forming hydrogen bonds and a duplex is formed. This process is known as molecular hybridisation. The procedure that combines Southern blotting and molecular hybridisation is known as Southern blot hybridisation. After this, the target DNA sequence is identified using autoradiography.

Question 5.
Agarose gel electrophoresis
Answer:
Agarose Gel Electrophoresis:
The molecules of nucleic acids are given uniform negative charge in alkaline buffer solution. These molecules then migrate towards the anode. The smaller molecules migrate faster than larger molecules because the rate of migration is inversely proportional to the molecular weight of separating molecules and directly proportional to the strength of electric field.

Question 6.
Cloning plasmid
Answer:
Plasmids were discovered by William Hayes and Joshua Lederberg (1952). These are extrachromosomal, self-replicating, usually circular, double-stranded DNA molecules, found naturally in many bacteria and also in some yeast. Although plasmids are usually not essential for normal cell growth and division, they often confer some traits on the host organism. For example, resistance to certain antibiotics or toxins that can be a selective advantage under certain conditions.

The plasmid molecules may be present as 1 or 2 copies or in multiple copies (500-700) inside the host organism. These naturally occurring plasmids have been modified to serve as vectors in the laboratory. The most widely used, versatile, easily manipulated vector pBR 322 is an ideal plasmid vector.

Question 7.
Cosmid
Answer:
Cosmid (cos + plasmid) vectors The term cosmid is a combination of two words. COS + MID. COS is taken from COS site of Lambda phage and MID is taken from plasmid DNA. Cosmid was developed for the first time by Collins and Honn (1978). The simplest cosmid vector contains a plasmid’s origin of replication, a selectable marker, suitable restriction enzyme sites and the lambda ‘cos’ site. Cosmids can be used to clone DNA fragments of upto 45 kb length.

Question 8.
Recombinant DNA
Answer:
Recombinant DNA is the DNA that has formed artificially by genetic engineering. It contain the gene of interest and it becomes the part of host’s genetic makeup where it further replication. The process of constructing recombinant DNA is called Recombinant DNA Technology (RDT).

Question 9.
Polymerase chain reaction
Answer:
A gene can also be cloned or amplified without the assistance of a host cell by a specific reaction, known as Polymerase Chain Reaction (PCR). PCR was discovered by Kary B. Mullis in 1983. The reaction is carried out in a thermocycler having a thermal cycling (heating and cooling) programme.

The target gene is put along with other substrates in the thermocycler. The DNA fragment, doubles at the end of the first cycle and quadruples after the second cycle and so on. In this amplification process, no host cell is used as the supporting system. It is carried out in three steps-denaturation, primer annealing and extension.

Question 10.
Micro injection
Answer:
Microinjection In this method, foreign DNA is directly injected into the nucleus of animal cell-or plant cell by using microneedles or micropip’ettes without any use of a vector DNA. It is used to v deliver a transgene or foreign DNA into the egg. Microinjection is especially used for transferring the foreign DNA in animal cells. The transgene is injected into the male pronuclei because it is larger and traceable with a dissecting microscope.

Long Answer Type Questions

Question 1.
Describe briefly about the making of a recombinant DNA.
Or Describe briefly recombinant DNA technology.
Answer:
Recombinant DNA Technology
Genetic engineering is alternately called as recombinant DNA technology or gene cloning. Paul Berg (1972) was ‘ awarded Nobel Prize in 1980 and is considered as father of genetic engineering. The first recombinant DNA (rDNA) was constructed by Stanley Cohen and Herbert Boyer in 1972. Recombinant DNA technology involves the following steps

1. Isolation of the genetic material (DNA) is carried out as follows
(a) DNA is enclosed within the membranes. To release DNA along with other macromolecules -such as RNA, proteins, polysaccharides and lipids, bacterial cells/plant or animal tissue are treated with enzymes such as lysozyme (bacteria), cellulase (plant cells), chitinase(fungus).
(b) Other molecules can be removed by appropriate treatments and purified DNA ultimately precipitates out as fine threads in the suspension after the addition of chilled ethanol.

2. Cutting of DNA at specific locations is done by using restriction enzymes. The purified DNA is incubated with the specific restriction enzyme at conditions optimum for the enzyme to act.

3. Isolation of desired DNA fragment is carried out using agarose gel electrophoresis.

4. Amplification of gene of interest using Polymerase Chain Reaction (PCR) is a reaction in which multiple copies of specific DNA (gene of interest) sequence are made (amplification) in-vitro.

5. Ligation of DNA fragment into a vector requires a vector DNA and source DNA.
(a) These are cut with endonuclease to obtain sticky ends.
(b) Both are then ligated by mixing vector DNA, gene of interest and enzyme DNA ligase to form recombinant DNA.

6. Insertion of recombinant DNA into the host cell/organism occurs by several methods, before which the recipient cells are made competent to receive the DNA.
(a) If recombinant DNA carrying antibiotic resistance gene (e.g. ampicillin), is transferred into E. coli cells, the host cell is transformed into ampicillin resistant cell.
(b) The ampicillin resistant gene can be called a selectable marker.
(c) When transformed cells are grown on agar plates containing ampicillin, only transformants will grow and others will die.

7. Culturing the host cells The cell containing the foreign gene is cultured on an appropriate medium at optimal conditions. The DNA gets multiplied.

8. Extraction of desired gene product is carried out in the following steps
(a) A protein encoding gene expressed in a heterologous host is called recombinant protein.
(b) Cells having genes of interest can be grown on a small or on a large scale.

CHSE Odisha Class 12 Biology Solutions Chapter 11 Microbes in Human Welfare

July 23, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 11 Microbes in Human Welfare Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 11 Question Answer Microbes in Human Welfare

Microbes in Human Welfare Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
In curd making, …………. is useful in coagulation of milk protein. (Lactobacillus, Saccharomyces, Penicillium, Aspergillus)
Answer:
Lactobacillus

Question 2.
Antibiotic streptomycin is obtained from ……….. (Streptomyces griseus, S. aureofaciens, S. nouresi, Saccharomyces cerevisiae)
Answer:
Streoptomyces griseus

Question 3.
Citric acid is produced when fermentation is caused by …………. (Lactobacillus, Aspergillus sp., Penicillium sp., Acetobacter sp.)
Answer:
Aspergillus sp.

Question 4.
Lipase enzyme is produced by the activity of …………. (Trichoderma viride, Rhizopus sp., Aspergillus sp., Saccharomyces cerevisiae)
Answer:
Rhizopus sp.

Question 5.
In pest control of crop plants ……………. has pesticidal properties, (baculovirus, papilloma virus, pox virus, Rhizobium)
Answer:
baculovirus

Express in one word only

Question 1.
What is called the process of heating and cooling of milk for inactivation of bacteria?
Answer:
Pasteurisation

Question 2.
What is called the secretions of microorganisms which are toxic to pathogenic bacteria?
Answer:
Antibiotics

Question 3.
What is the commercial name of acetic acid?
Answer:
Vinegar

Question 4.
What is called the accumulated microorganisms and organic matter in the treatment of sewage?
Answer:
Sludge

Question 5.
What is the major component of biogas?
Answer:
Methane

Question 6.
What can be called the natural pest killing agent other than artificial chemical?
Answer:
Biopesticides

Question 7.
What is called the association between Rhizobium in the root system of legumes?
Answer:
Symbiotic association

Correct the sentences, if required, by changing the underlined word(s)

Question 1.
Antibiotic tetracyclin is obtained from Penicillium notatum.
Answer:
penicillin

Question 2.
In biogas, methane is produced due to the activities of nitrogen-fixing bacteria.
Answer:
methanogenic

Question 3.
The first antibiotic extracted from bacterial culture is nystatin.
Answer:
streptomycin

Question 4.
Industrial production of organic acids through microbial cultures is due to the oxidation process by bacteria.
Answer:
fermentation

Question 5.
Acetic acid is produced by Lactobacillus sp.
Answer:
Lactic acid

Fill in the blanks

1. In biogas production ………… bacteria are used.
Answer:
methanogenic

2. BGA used in biological nitrogen-fixation are called ………….. bacteria.
Answer:
cyano

3. Ethanol obtained by ………….. fermentation is used in industry.
Answer:
microbial

4. Acetobacter converts ……………. to vinegar by aerobic fermentation of legumes.
Ans.
ethyl alcohol

Short Answer Type Questions

Write notes on the following with atleast 3 valid points

Question 1.
Biogas
Answer:
It is a complex mixture of gasese like CH₄,CO₂, H₂, etc., that is produced by anaerobic digestion of biomass. It is used as fuel.

Question 2.
Biopesticides
Answer:
These are biodegradable, highly pest specific biological agents that are used to control pest population without harming the environment.

Question 3.
Biofertilisers
Answer:
These are the preparations containing microorganisms that help the plants to uptake various nutrients in utilisable form, e.g. Rhizobium, BGA, etc.

Question 4.
Microbes in industry.
Answer:
Industrial use of microbes includes the production of beverages, antibiotics, etc., that are useful for the human. The large scale production of these products is carried out in bioreactors using the appropriate microbes, e.g. butyric acid is derived from Clostridium and terramycin is derived from Streptomyces rimosus.

Question 5.
Microbes in antibiotics production.
Answer:
The term ‘antibiotics’ was coined by Waksman (1942), and it is derived from the Greek words Anti-against and bios-Yiit, together they mean ‘against life’ (with reference to disease causing organisms). Antibiotics are the chemical substances, produced by some microbes that can kill or retard the growth of other disease causing microbes.

The first antibiotic was obtained from the species of Penicillium notatum in 1928 by Sir Alexander Fleming and it was named Penicillin.

Question 6.
Microbes in sewage treatment.
Answer:
Sewage refers to the municipal waste water generated everyday in cities and towns. Human excreta is the major component of it. It contains large amounts of organic matter and microbes, out of which many are pathogenic. So, it cannot be discharged directly into natural water bodies like rivers, streams, etc.

Differentiate between two words in the following pairs of words

Question 1.
Chemical fertilisers and Biofertilisers.
Answer:
Differences between chemical fertilisers and biofertilisers are as follows

Chemical fertilisers	Biofertilisers
These are industry made products which are used to increase the output of a crop plant.	These are the microorganisms which increase the nutrient level of soil.
These are harmful and cause pollution to water bodies as well as ground water.	These are not harmful as they lead to nutrient enrichment in an organic way.

Question 2.
Synthetic pesticides and Biopesticides.
Answer:
Differences between synthetic pesticides and biopesticides are as follows

Synthetic pesticides	Biopesticides
These are not very specific, so harm non-targeted species.	These are highly specific, so do not harm non-targeted species.
They cause pollution.	They do not cause pollution.
Insects may become resistant, e.g. Heliothis, has become resistant to most insecticides.	Insects are not expected to develop resistance to biopesticides.
Harmful residues may often remain in food, fodder and fibres.	No harmful residues remain in food, fodder and fibres.

Question 3.
Baker’s and Brewer’s yeast.
Answer:
Differences between baker’s and brewer’s yeast are as follows

Baker’s yeast	Brewer’s yeast
Baker’s yeast is Saccharomyces cerevisiae. It is used in fermentation to prepare dough that is used to make bread, idli, dosa, etc.	Brewer’s yeast is also Saccharomyces cerevisiae, but a different strain. It is used to produce various alcoholic drinks by fermenting malted cereals and fruit juices.
In this, CO₂ released during the process of fermentation gives the fluffy appearance.	In this, CO₂ released does not cause any fluffy appearance.

Question 4.
Symbiotic nitrogen-fixation and Mycorrhizal nitrogen-fixation.
Answer:
Differences between symbiotic nitrogen-fixation and mycorrhizal nitrogen-fixation are as follows

Symbiotic nitrogen-fixation	Mycorrhizal nitrogen-fixation
It is a mutually beneficial association of bacteria with the plants for food and shelter.	It is a mutually beneficial association of fungus with the root of higher plants.
The most common is Rhizobium which resides in root nodules of leguminous plants and fixes nitrogen.	Members of genus Glomus form mycorrhizal association.

Long Answer Type Questions

Question 1.
Give a detailed account of industrial application of microbes.
Answer:
Industrial Products:
A variety of microbes are used to synthesise a number of products in large scale that are valuable to human beings, e.g., beverages, antibiotics, etc.
A microbe should have following characteristics for its application in industrial fermentation.

It should be non-pathogenic and its raw materials should be cheap and easily available.
It should have the ability to grow rapidly on suitable nutrients.
It should have the ability to high yield of desired products consistently in a reasonable time.
It should possess high levels of enzymes for rapid production of the end products.

Now-a-days a number of products are obtained on commercial level with the help of microbes. To accomplish this, microbes are grown in very large vessels called fermentors or bioreactors.
Some of the industrial products obtained using microbes are as follows

Antibiotics:
The term ‘antibiotics’ was coined by Waksman (1942), and it is derived from the Greek words Anti-against and bios-Yiit, together they mean ‘against life’ (with reference to disease causing organisms). Antibiotics are the chemical substances, produced by some microbes that can kill or retard the growth of other disease causing microbes.

The first antibiotic was obtained from the species of Penicillium notatum in 1928 by Sir Alexander Fleming and it was named Penicillin.

It was obtained at commercial scale by growing the microbe in fermentor. The medium used for growing microbe, contained a carbohydrate as energy source, mineral salts and corn steep liquor. The culture was kept under vigorous aeration to obtain the maximal production of ‘penicillin’. It was called the wonder drug as it was used during second World War to give relief to the wounded soldiers from pain and suffering.
Antibiotics and Their Sources

Antibiotic	Sources	Action
Penicillin	Penicillium chrysogenum, P. notatum.	Tonsilitis, sore throat, gonorrhoea.
Streptomycin	Streptomyces griseus	Pneumonia, tuberculosis and local infections.
Erythromycin	Streptomyces erythreus	Typhoid, diphtheria, whooping cough.
Terramycin	Streptomyces rimosus	Intestinal and urinary infections.
Tetracyclines	Streptomyces aureofaciens	Eye infections.
Chloramphenicol	S. venezuelae	Conjunctivitis.
Nystastin	S. nouresi	Candida infection.
Polymixin	Bacillus polymyxa	Antifungal.

The second antibiotic, streptomycin was obtained from the bacterium Streptomyces griseus. The bacteria were grown on culture medium containing glucose, soyameal and mineral salts at pH 7.4 -7-5.

The fermentation was carried out under submerged condition at 25-30°C for 5-7 days. Now-a-days industrial fermentation is used to produce several antibiotics against diseases which have earlier caused widespred destruction in the form of epidemics.

Alcoholic Beverages:
Earlier, people used to produce alcohol by fermentation. Later, another method was used for the same which included catalytic hydration of ethylene. In modern time, again fermentation process is used for the production of ethanol.

It is used for dual purpose, i.e. as chemical and as fuel. Sugar-beet, potatoes, corn, cassava and sugarcane, etc., are used as substrate for the production of ethanol.

Yeasts (like Saccharomyces cerevisiae, S. uvarum, S. carlsbergensis), Candida brassicae, C. utilis and bacteria (Zymomonas mobilis) are used for the production of ethanol at industrial scale. The type of alcoholic drink depends upon the raw material used for its production.

Beer is obtained by the fermentation of barley grains while wine is produced by grapes. This process of alcohol production is known as brewing. In this process, CO₂ is produced as a byproduct which is further used in bakery to provide sponginess to breads, cakes, etc.

Production of Organic Acids:
These are produced by the metabolic actions of microbes, i.e. microbial fermentation. Important organic acids producing organisms are listed below

Organic Acid	Microbes involved
Citric acid	Aspergillus niger and Penicillium sp. (fungi)
Acetic acid	Acetobacter aceti (bacteria)
Butyric acid	Clostridium butylicum (bacteria)
Lactic acid	Lactobacillus (bacteria)
Gluconic acid	Aspergillus niger and P. chrysogenum
Fumaric acid	Penicillium sp.

The methods of production of some organic acids are as follows

Acetic acid The production of acetic acid or vinegar occurs in two steps-preliminary fermentation and secondary fermentation. Former involves production of ethyl alcohol while later involves the production of acetic acid under aerobic conditions.
Lactic acid It is produced with the help of Lactobacillus. The starchy substances, e.g. corn starch, potato starch, molasses and whey, etc., are initially hydrolysed to obtain simple sugars. It is followed by fermentation under suitable environmental conditions.
Citric acid It is produced by the fermentation of beet molasses, sucrose, commercial glucose, starch hydrates, etc. Many fungi, bacteria and yeasts are used for the same.

Use of Organic Adds:
Organic acids are used as preservatives, flavour enhancers and flavouring agent. They are also used to prevent oxidation and turbidity of food products.

Production of Enzymes:
When microbes are grown in culture medium, they release various substances in the medium including enzymes. These substances can be extracted from the medium and can be used for various purposes like enzymes are used in pharmaceutical, food and textile industries. The quality and quantity of enzymes depend upon the microbial strain and cultural conditions.

Some enzymes and their applications have been discussed below

Lipase produced by Rhizopus sp., used in detergent formulations and helps in removing oily stains from the laundry due to its digestive application.
Pectinase produced by Aspergillus sp., used for clarifying bottled fruit juices.
Proteases They are produced by Aspergillus niger and Bacillus subtilis. They are used as clarifying agents for beer, meat tenderizer, etc.
Amylase produced by Aspergillus sp., used for digestive purpose and in the preparation of glucose syrup.
Cellulase produced by Trichoderma viridie, used for the degradation of cellulose.

Streptokinase produced by Streptococcus and modified by genetic engineering is used as a clot buster for removing clots from blood vessels of patients, who have undergone myocardial infarction leading to heart attack.

Production of Bioactive Molecules:
The bioactive molecules produced by microbes are

Cyclosporin-A It is produced by Trichoderma polysporum (fungus). It is used as an immunosuppressive agent for the patients, who have undergone organ transplantation.
Statins They are produced by Monascus purpureus (yeast) and are used as blood cholesterol lowering agents.

Question 2.
Explain how microbes are useful in pollution control and also in production of alternative source of energy.
Answer:
Microbes are major component of biological world on this earth. Although they are the causal agents of most of the infectious diseases, still they are of great importance to humans. Now, scientist are working on the ways in which with the use of microorganisms pollution problem can be solved. This can be done by bioremediation. In this technique microorganisms are used to neutralise pollutants from a contaminated site by their oxidation. Pollution can be controlled by microbes in two ways

By enhancing the growth and activity of microbes already present an pollutant site.
By adding some new microbes to the pollution site. Pollution control by the application of microbes works best when pollutants are a known mixture of organic compounds that are related to each other in structure and when there is no competition from indigenous microorganisms.

Production of Alternative Source of Energy :

Microbes in Biogas Production:
The excreta of cattle, commonly called gobar, is rich in methanogenic bacteria. Thus, cattle dung can be used for the generation of biogas, commonly called gobar gas. As cattle dung is available in large quantities in rural areas this method of biogas production is mostly functional in those areas.

Economically viable biogas is produced in large vessels called bioreactors.
Biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and slurry of dung is fed. A floating cover is’placed over the slurry, which keeps on rising, as the gas is produced in the tank due to the microbial activity.

Methanobacterium present in the dung acts on the bio-waste to produce biogas. An outlet is also present which connects to a pipe that supplies biogas to the nearby houses.
Img 1

There is another outlet from which spent slurry is removed that can be used as fertiliser. Biogas production technology was developed in India mainly by Khadi and Village Industries Commission (KVIC) and Indian Agricultural Research Institute (LARI).

The production of biogas occurs in following three steps

Solubilisation: Decomposition of lipids, proteins, cellulose, hemicellulose, etc., present in organic matter to monomers by the action of hydrolytic enzymes like lipases, cellulases, proteases, peptidases, etc., secreted by microorganisms.

Acidogenesis: Conversion of monomers to organic acids with the help of fermentative microbes, e.g. Propionibacterium, Acetovibrio. The most common organic acid produced is acetic acid.

Methanogenesis: Biogas production with the action of methanogens, e.g. Methanococcus Methanobacillus.

CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production

July 22, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 10 Question Answer Improvement in Food Production

Improvement in Food Production Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Fill in the blanks with correct answers from the choices given in the brackets of each bit

1. Physical removal of anthers is done by …………… process.
(introduction, mutation, hybridisation, emasculation)
Answer:
emasculation

2. The cross between two varieties of same crop is called ………… hybridisation. (intervarietal, intravarietal, intrageneric, intergeneric)
Answer:
intervarietal

3. In the process of breeding, genetic makeup of ……….. the concerned organism may be changed, (mutation, interspecific, selection, intraspecific)
Answer:
mutation

4. The plant part used in tissue culture is called …………… .(cells, zygote, explant, gamete)
Answer:
explant

5. To produce haploid plants ………… culture can be made.
(anther, embryo, endosperm, zygote)
Answer:
anther

6. The autotroph ………… is cultured to obtain single cell protein.
(Saccharomyces, Pseudomonas, Spirulina, Chaetomicem)
Answer:
Spirulina

Multiple choice questions

Question 1.
The cross breed milch breed is
(a) Red Sindhi
(b) Tharparkar
(c) Frieswal
(d) Sahiwal
Answer:
(c) Frieswal

Question 2.
The exotic breed of cattle is
Or Which is an exotic breed of cattle?
(a) Jersey
(b) Sahiwal
(c) Gir
(d) Red Sindhi
Answer:
(a) Jersey

Question 3.
An indigenous breed of cattle is
(a) Red Dane
(b) Jersey
(c) Karan Swiss
(d) Rathi
Answer:
(d) Rathi

Question 4.
Sunandini, a cross breed cattle is produced by crossing.
(a) Brown-Swiss bull with Sahiwal cow
(b) Jersey bull with Red Sindhi cow
(c) Red Dane bull with Sahiwal cow
(d) Holstein-Friesian bull with Rathi cow
Answer:
(a) Brown-Swiss bull with Sahiwal cow

Question 5.
An indigenous milch breed of buffalo is
(a) Haryana
(b) Jaffarabadi
(c) Kankrej
(d) Jamunapuri
Answer:
(b) Jaffarabadi

Question 6.
The indigenous breed of poultry is
(a) Nicobari
(b) Rhode Island Red
(b) Barred Plymouth Rock
(d) New Hampshire .
Answer:
(a) Nicobari

Question 7.
Commercial poultry production is done under
(a) free range system
(b) intensive system
(c) semi-intensive system
(d) folding unit system,
Answer:
(b) intensive system

Question 8.
Which of the following is a disease of cattle
(a) Ranikhet disease
(b) Marek’s disease
(c) bacillary white diarrhoea
(d) All of the above
Answer:
(d) All of the above

Express in one or two word(s)

1. What is the nutrient source not required for obtaining single cell protein from autotrophs ?
Answer:
Carbon source

2. What is called to the amorphous mass of loosely arranged thin-walled parenchymatous cells developed in the process of tissue culture?
Answer:
Callus

3. What is called to the remaining part of plant cells when its wall is mechanically or enzymatically removed?
Answer:
Protoplast

4. What is called to the sum total of all the alleles of gene present in a particular species and its allied wild and cultivated varieties?
Answer:
Gene pool

5. What is the process called, where flower buds are artificially enclosed to avoid undesired pollination?
Answer:
Bagging

6. In which process can genetic makeup of concerned organism changed ?
Answer:
Mutation

7. The preservation of semen at ultra low temperature.
Answer:
Cryopreservation

8. The substance the queen bee is fed with.
Answer:
Royal jelly

9. Development of haploid eggs without fertilisation.
Answer:
Parthenogenesis

10. The important monosaccharide present in honey.
Answer:
Levulose

11. The repeated breeding between closely related individuals.
Answer:
Upgrading

12. Breeding between unrelated individuals.
Answer:
Cross-breeding

Correct the sentences, if required by changing the underlined word only

1. The process of aseptic transfer of explant from nutrient medium to culture vessels is called micropropagation.
Answer:
inoculation

2. When cytoplasms are fused and one of the two nuclei lost in formation of new organism, it is called a hybrid.
Answer:
cybrid

3. For nuclear fusion, PEG is used.
Answer:
protoplast fusion

4. Cross between different genotypes of same variety is called intrageneric hybridisation.
Answer:
intravarietal

5. When pollens from selected male parents are transferred to stigma, it is called natural pollination.
Answer:
cross

Fill in the blanks

1. The cross between two species of a genus is called …………. hybridisation.
Answer:
intrageneric

2. In selection and testing of superior recombinants, F₁-generation offsprings are …………… pollinated.
Answer:
self

3. Biofortification is done to enrich crops with micronutrients like minerals and ………. .
Answer:
vitamins

4. Explants sterilised by mercuric chloride or hydrogen peroxide, etc. are known as ………….. sterilisation.
Answer:
surface

5. Through the process of tissue culture, large number of plants raised in a small area and called micropropagation or ……. propagation.
Answer:
clonal

6. Triploids can be raised by ……….. culture.
Answer:
endosperm

7. Milk yielding cattle breeds are known as ………… breeds.
Answer:
milch

8. Foot and mouth disease is a common disease of ………
Answer:
cattle

9. Traditional method of breeding is substituted by artificial ………. .
Answer:
insemination

10. The housing system employed in the commercial poultry farming is known as ……….. farming.
Answer:
intensive system

11. Ranikhet disease is a common disease of …………..
Answer:
poultry

12. Culture of honeybee on a commercial basis is known as ……………
Answer:
apiculture

13. The drones develop from haploid eggs, which are not fertilised. This development is termed as …………….
Answer:
parthenogenesis

14. The deserting of the queen bee is known as ……………… .
Answer:
swarming

15. The characteristic flight of the queen bee during fertilisation is known as …………..
Answer:
nuptial flight

16. The juvenile bees are reared in …………. chamber of the honey comb.
Answer:
brood

17. The worker bees develop from fertilised eggs and hence are diploid ………….. .
Answer:
sterile females

Short Answer Type Questions

Answer the following within 50 words each

Question 1.
Name five indigenous breeds of cattle.
Answer:
Indigenous Milch Breeds of Cattle
The indigenous breeds of cattle are classified into

Milch breeds These are high milk producers.
Dual purpose breeds In these breeds, cow yield average quantity of milk, while males are good working bullocks.
Draught breeds These include poor milkers but superior quality bullocks.

These breeds are the highest milk producing catde. These include Sahiwal, Red Sindhi, Gir, Tharparkar and Rathi.

Question 2.
Name three cross-breeds of cattle.
Answer:
Cross-Breed Strains of Cattle:
Some of the cross-breed cows are as follows
(a) Karan Swiss This breed was developed at National Dairy Research Institute ‘Karnal, by the breeding of Sahiwal cows with Brown Swiss bulls imported from USA.
(b) Karan Fries This breed has got its origin at the National Dairy Research Institute, Karnal by the crossing between Tharparkar and Holstein-Friesian.
CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production 1
(c) Sunandini This breed originated in Kerala by crossing the local non-descript cattle with Jersey, Brown Swiss and Holstein-Friesin breeds.
(d) Frieswal This breed is developed by crossing Holstein-Friesian bulls with Sahiwal cows.

Question 3.
Name three exotic breeds of cattle.
Answer:
Exotic Milch Breeds of Cattle
This breed includes high milk producing cattle breeds of other countries which have been cross breed with indigenous breeds for producing high yielding hybrids which can easily adopt to Indian conditions.
The common exotic breeds which are used in such programme include Holstein-Friesian of Netherlands, Brown-Swiss of Switzerland, Jersey of Europe and America and Red Dane of Denmark.
Img 2

Question 4.
What is cryopreservation?
Answer:
Cryopreservation is the preservation of tissues, embryos gametes, etc., at -196°C (liquid nitrogen), the preserved material is revived through special technique when required. Cryopreservation methods seek to reach low temperatures without causing additional damage caused by the formation of ice during freezing. Traditional cryopreservation has relied on coating the material with cryoprotectants.

Question 5.
Describe organic dairy farming
Answer:
Organic Dairy Farming
Though the milk production has increased by leaps and bounds by the use of synthetic chemicals on cattle and buffaloes, there is a chance of contamination of the harvested milk. It has been found that milk and milk products are contaminated by residue components of harmful chemicals.

Question 6.
What is free-range poultry farming?
Answer:
The term ‘poultry’ means rearing of domesticated fowl (birds) for food (meat) or their eggs, i.e. chicken, ducks, , geese, turkeys and some varieties of pigeons. Poultry farming upto 1960 was considered under free-range condition.

Free-range system In this system, the birds are allowed to move freely to outside. The farmer provides them with food supplements as requird moving outside.

Question 7.
What is intensive housing system in poultry?
Answer:
Intensive system
This system is practiced where there is a need of a large scale production of meat and eggs. The birds do not have access to outside and are kept in a walled house. There are two types of housing system. Cage system is the system, where birds are kept in cages and it also helps in preventing the spread of diseases. In litter system however, birds are kept on a floor covered with rice husk, saw dust, dried leaf, etc.

Question 8.
Describe the protein source in poultry nutrition.
Answer:
These are required for growth and repair of the body tissues. For protein, the feed is supplemented with soyabean meal, groundnut cake, sunflower cake.
The fish meal prepared from the wastes of fish processing industry and meat meal from the wastes of meat processing industry are also used to feed poultry birds. The skimmed milk is highly nutritive for young chicks and should be given in clean vessels. The green foods such as fresh tender grass, garlic lettuce, onions, etc. are important part of the feed.

Fats Only unsaturated fats could be digested by poultry. This requirement is met by providing groundnut, cake, sunflower cake, etc.

Minerals Some minerals are required in large quantity such as calcium, sodium, etc. Minerals such as zinc, iron, copper, are required in lesser quantities and so, are called as trace minerals.

Vitamins fat soluble (A, D, E, K) and water soluble (B,C) all are essential for normal growth of chickens.
CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production 2

Question 9.
Why is inbreeding harmful?
Answer:
Breeding between the animals of the same breed for 4-6 generation is called inbreeding. It increases homozygosity. Thus, inbreeding is necessary to develop pureline. It also helps in accumulation of superior genes and elimination of less desirable genes. But continued inbreeding reduces fertility and even productivity so, it is harmful also.

Question 10.
What is artificial insemination?
Answer:
Artificial Insemination
It is a method in which the semen collected from a superior male parent is injected into the reproductive tract of the selected female parent by the breeder. This results in development of progeny with superior traits like better growth and increased milk production.
The success rate of artificial insemination is fairly low, even then it is carried out because of the following advantages

The semen collected can be used immediately or stored in frozen form for later use.
The semen from a desired breed can be easily transported in the frozen form to distant places, where the selected females are present and thus can be used for impregnating the females on a large scale.
It helps to overcome several problems of normal mating.

Question 11.
What is in vitro fertilisation?
Answer:
In Vitro Fertilisation and Embryo Transfer
In this modern method of animal breeding, eggs of an ovulating livestock animal, e.g. cattle are isolated. Then they are fertilised in- vitro by semen of a bull which possesses desired characters.

This fertilised egg is kept in a suitable medium and is then stimulated to undergo cleavage to a 8-16 called stage embryo which is known as a blastocyst, also in-vitro. This embryo is then finally transferred or implanted into uterus of a surrogate cow and made pseudopregnant.
The cow completes the term and then give birth to calf with the required characters.

Question 12.
What is a transgenic animal?
Answer:
Transgenic Animals:
It involves the transfer of genes intti special cells or embryos. In this method, the unfertilised egg is enucleated by treating with cytochalasin-B and the blastula stage nuclei are obtained from embryo donor. These two are incubated together in’the presence of Polyethylene Glycol (PEG) and transferred into surrogate mother for fusion. The foetus develops into a transgenic animal. Various products like a-antitrypsin, haemoglobin, lacteferrin, iron binding protein, etc., are obtained from transgenic animals. In Japan, gynogenesis is being used to improve fish size.

Question 13.
Describe swarming.
Answer:
Swarming It is the process by which a new honeybee colony is formed when the queen bee leaves the colony with a large group of worker bees.
Swarming is mainly a spring phenomenon, usually within a two or three weeks period depending on the locality but occasional swarms can happen throughout the producing season.

Write notes on with 2/3 valid points

Question 1.
Germplasm collection
Answer:
Collection of Germplasm:
This is the major step acting as the root of any breeding programme. In this step, the pre-existing genetic variability available in purelines, wild varieties, species no longer cultivated and relatives of many crop species are collected and preserved.

Evaluation of their characteristics is a pre-requisite for the effective exploitation of natural genes available in the populations. The entire collection of plants/seeds having all diverse alleles for all genes in a given crop is called germplasm collection. A good germplasm collection is essential for a successful breeding programme.

Question 2.
Emasculation
Answer:
Emasculation
It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used.

For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.

Question 3.
Bagging
Answer:
Bagging In this method, the emasculated flower or inflorescence is immediately bagged to avoid . pollination by any foreign pollen. Emasculation bags made up of butter paper, fine cloth or polythene, etc., may be used depending upon the crop.

Question 4.
Artificial pollination
Answer:
Artificial pollination In order to bring about artificial pollination, the collected pollen grains from selected male parents are dusted on the stigma of female plant. The properly labelled flowers are then allowed to cross-pollinate. The crossed flowers are then tagged again.

Question 5.
Breeding for disease resistance
Answer:
Resistance of the host plant is the ability to prevent the pathogen from causing disease and is determined by the genetic constitution of host plant. Crops are required to be disease resistant, as there are a wide range of fungal, bacterial and viral pathogens that affect the yield of cultivated crop species, especially in tropical climates.

Question 6.
Biofortification
Answer:
It is a method of breeding crops with higher levels of vitamins, minerals, healthier fats to improve public health. The objective of breeding for improved nutritional quality is to enhance
(i) Protein, oil content and quality.
(ii) Vitamin content.
(iii) Micronutrients and mineral content

Question 7.
Explant
Answer:
It is the technique of maintaining and growing plant cells, tissues or organs in nutrient media under controlled environmental conditions. The plant part taken out to be grown in a test tube in special nutrient media is called explant.

Explant Selection:
It is the tissue obtained from the plant for the purpose of tissue culture. The most commonly used explant tissues are the meristematic ends of the plants. These include stem tip, auxiliary bud tip and root tip. Meristematic tissues have high rate of cell division. Before the procedure starts, explants are cleaned and surface sterilised with the help of disinfectants and detergents to remove germs.

Question 8.
Tissue culture medium
Answer:
Tissue Culture Techniques and Steps
Plant tissue culture involves producing entire plants from a few plant cells or tissues by growing them in an artificial medium.

1. Explant Selection
2. Sterilisation
3. Preparation of Nutrient or Culture Medium
4. Inoculation
5. Callus Formation and its Culture
6. Organogenesis
7. Somatic Embryogenesis

Question 9.
Totipotency .
Answer:
Totipotency The capacity to generate a whole plant from any cell/ explant is called cellular totipotency in fact, the whole plant can be regenerated from any plant part or cells.

Question 10.
Micropropagation
Answer:
Micropropagation or Clonal Propagation
By the process of plant tissue culture which requires lesser space and lesser time, a large population of plants could be raised. Also since the plants produced are genetically identical, this process is also called as clonal propagation. Examples of plants cutlivated micropropagation include grapes, bamboo, coffee, banana, cardamoms, etc.

Question 11.
Anther culture
Answer:
This technique was developed by Guha and Maheshwari (1946) in Datura innoxia. In this technique, floral buds are opened to remove anthers. These anthers are then cultured for the production of haploid embryoids. The plants produced by haploid culture are sterile. These haploids could be subjected to colchicine treatment in order to double their chromosome number.

Question 12.
Somaclonal variation
Answer:
Somaclonal variation Genetic variation present among plant cells of a culture is called somaclonal variation.
The term somaclonal variation is also used for the genetic variation present in plants regenerated from a single culture.

Question 13.
Synthetic seeds
Answer:
Synthetic Seeds/Artificial Seeds:
Artificial seeds are those seeds in which somatic embryos or plantlets are encapsulated by calcium alginates. This can put a stop to desiccation and they could be used by farmers like normal seeds and are also used for rapid propagation of crop plants.

Question 14.
Secondary metabolites
Answer:
Secondary Metabolites Production:
Cell suspension culture has been employed for commercial production of secondary metabolites like tannin, latex, resin. These cost of secondary metabolites production would be very high if manufactured chemically. So, the plant tissue culture comprising of large scale cell suspension culture has been used.

For example, taxol which is an anticancer drug is obtained from Taxus. The cells of Taxus are cultured which produce a similar chemical which is later chemically modified to taxol. Another example includes Digitalis lantana which is being employed to modify digoxin, to digitoxin, a drug used in cardiac treatment.

Question 15.
Embryo rescue
Answer:
Endosperm Culture:
It is used to produce triploids. Endosperm culture is helpful in producing seedless apple, Citrus which are of better commercial values.

Differentiate between the following

Question 1.
Bagging and Tagging.
Answer:
Differences between bagging and tagging are as follows

Bagging	Tagging
It is the step involved in hybridisation.	It is also a step of hybridisation.
Emasculated flowers are immediately covered by paper, plastic or polythene bags.	Bapqed flowers tagged by writing date, time, male and female, parents.

Question 2.
Chemical pest control and Biological pest control.
Answer:
Differences between chemical pest control and biological pest control are as follows

Chemical pest control	Biological pest control
In this method chemicals are used for pest control.	In this method biological organisms, i.e predator, parasitoids are used for pest control.
Various types of chemicals are used, i.e herbicides, insecticides, pesticides, etc.	Various predators, i.e Trichoderma, B. thuringiensis, etc. are used.
These are expensive.	These are cost effective methods.

Question 3.
Callus and Protoplast.
Answer:
Differences between callus and protoplast are as follows

Callus	Protoplast
It is a growing mass of unorganised plant parenchyma cells.	It refers to entire cell excluding cell wall.
Explants are supplemented with auxin, cytokinin, etc to initiate callus.	It is used to study membrane biology, protoplast fusion, etc.

Question 4.
Synthetic seeds and Embryo.
Answer:
Differences between synthetic seeds and embryo are as follows

Synthetic seeds	Embryo
These are encapsulated somatic embryo, shoot buds or aggregates of cell or any tissues which has the ability to form a plant in in vitro.	It is the part of seed, consisting of precursor tissues for the leaves, stem and roots.
Hybrid plants can be easily propagated using synthetic seeds.	Embryo culture is used for the culturing of embryo.

Question 5.
Endosperm culture and Anther culture
Answer:
Differences between endosperm culture and anther culture are as follows

Endosperm culture	Anther culture
Endosperm is used for culturing.	Anther is used for culturing.
Triploid plants are formed.	Haploid plants are formed.
Used in production of seedless fruits.	It is useful for the improvement of crop plants.

Question 6.
Hybrid and Cybrid.
Answer:
Differences between hybrid and cybrid are as follows

Hybrid	Cybrid
It is the result of combining the qualities of two organisms of different breeds, varieties, species through hybridisation.	It is a eukaryotic cell produced by the fusion of two protoplast.
Hybrids are produced through hybridisation.	These are produced through somatic hybridisation.

Long Answer Type Questions

Question 1.
Describe the main steps of breeding to develop genetic variability in crop plants.
Answer:
Steps in Plant Breeding:
The major steps in breeding a new genetic variety of a crop are
(i) Collection of Germplasm:
This is the major step acting as the root of any breeding programme. In this step, the pre-existing genetic variability available in purelines, wild varieties, species no longer cultivated and relatives of many crop species are collected and preserved.

(ii) Evaluation and Selection of Parents:
It is carried out by evaluating germplasm, to identify plants with desirable combination of characters.
The selected plants are multiplied and hybridised by self-pollination. Purelines are created, whenever desired and possible.

(iii) Cross Hybridisation among Selected Parents
It is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in a single plant. It is known to be a time consuming and tedious process as it involves collection of pollen grains from the desired plants (male parent) and have to be placed on the stigma of the selected flower (female parent) to incorporate desired traits.

It is also not necessary that the hybrids do combine desired characters. The chances of desirable combination is usually only one in few hundred to a thousand crosses carried out.

Some of the objectives of hybridisation are as follows
(a) To produce variations in progeny which are useful. It is achieved by recombination of characters.
(b) To make the use of hybrid vigour which is the superiority of progeny over its parents.
(c) To develop high yielding varieties which are also resistant to diseases.

Depending on the nature of plants involved in the cross, there may be different types of hybridisation such as
(a) Inter-varietal Cross between two varieties of same crop.
(b) Intra-varietal Cross between different genotypes of the same variety.
(c) Intra-generic Cross between two species of a genus.
(d) Inter-generic Cross between two genera.

Techniques of Hybridisation:
The first step in hybridisation is to ensure that pollination can not occur before the intended artificial process. This can be achieved by
(a) Emasculation It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used. For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.

(b) Bagging In this method, the emasculated flower or inflorescence is immediately bagged to avoid pollination by any foreign pollen. Emasculation bags made up of butter paper, fine cloth or polythene, etc., may be used depending upon the crop.

(c) Tagging In this process, the emasculated and bagged inflorescence or flowers are tagged and properly labelled.
The labels contain following information

1 Date of emasculation
2 Date of pollination
3 Name of female and male plants. The name of the female parent plant is written first and that of the male parent plant is written later.

(d) Artificial pollination In order to bring about artificial pollination, the collected pollen grains from selected male parents are dusted on the stigma of female plant. The properly labelled flowers are then allowed to cross-pollinate. The crossed flowers are then tagged again.

(e) Selection and testing of superior recombinants:
This step consists of selection of plants among the progeny of the hybrids with desired combination of characters. It yields plants that are superior than both the parents. This is known as hybrid vigour/heterosis. These are self-pollinated for several generations, till they reach a state of uniformity or homozygosity, so that the characters will not segregate in the progeny.

(f) Testing, release and commercialisation of new varieties Evaluation is done for newly selected lines for their yield and other agronomic traits of quality, disease resistance, etc. Selected plants are grown in research fields and their performance is recorded under ideal fertiliser applications, irrigation and other crop management practices.

Testing of hybrid line is done in farmer’s field after evaluation. After testing, the crop is grown at different locations in the country with different agroclimatic zones for atleast three growing seasons. The tested material is evaluated in comparison to the best available local crop cultivar used as reference cultivar. Release of tested material is finally done in bulk after selection and certification.

Examples of Some Improved Varieties
(i) Wheat Kalyan Sona and Sonalika are semi-dwarf, high yielding and resistant to root disease, introduced to wheat growing belt of India.
(ii) Rice Along with the above wheat varieties, rice varieties such as IR – 8 and Taichung and their derivatives Jaya and Ratna varieties were introduced around the same time in India. All these varieties contributed to the quantum jump in food production which is called green revolution.

Question 2.
Describe the techniques of hybridisation.
Answer:
Techniques of Hybridisation:
The first step in hybridisation is to ensure that pollination can not occur before the intended artificial process. This can be achieved by
(a) Emasculation It is the process of removal of stamens of a flower, without affecting the female reproductive organs. Emasculation is usually done in bisexual flowers before the anthers mature and stigma has become receptive. It can be done by various methods, such as, hand emasculation, suction method, hot water emasculation, alcohol treatment, cold treatment and genetic emasculation. Among these methods, hand and suction method are mostly used. For example, in Triticum (wheat) flowers may be exposed to some chemical like 2,4-dichloro phenoxyacetic acid, maleic hydrozide or a panicle of Sorghum is dipped in lukewarm (50°C) water for 10 minutes, etc. These methods are applied on those cases where the methods of physical nature could not be applied.

(c) Tagging In this process, the emasculated and bagged inflorescence or flowers are tagged and properly labelled.
The labels contain following information

1 Date of emasculation
2 Date of pollination
3 Name of female and male plants. The name of the female parent plant is written first and that of the male parent plant is written later.

Question 3.
Give an account of techniques and steps of plant tissue culture.
Answer:
Tissue Culture:
It is the technique of maintaining and growing plant cells, tissues or organs in nutrient media under controlled environmental conditions. The plant part taken out to be grown in a test tube in special nutrient media is called explant.
The capacity of producing a whole plant from this explant is called totipotency.

It was Gottilieb Haberlandt (1902) who discovered totipotency. Haberlandt also attempted to cultivate plant leaf cells for the first time in simple nutrient medium. Plant tissue culture technique is a major tool in various areas of crop improvement, experimental biology and fundamental or applied research.

Tissue Culture Techniques and Steps:
Plant tissue culture involves producing entire plants from a few plant cells or tissues by growing them in an artificial medium.

1. Explant Selection
It is the tissue obtained from the plant for the purpose of tissue culture. The most commonly used explant tissues are the meristematic ends of the plants. These include stem tip, auxiliary bud tip and root tip. Meristematic tissues have high rate of cell division. Before the procedure starts, explants are cleaned and surface sterilised with the help of disinfectants and detergents to remove germs.

2. Sterilisation
For plant tissue culture, it is essential that the explants, culture vessel, media and instruments, etc. are free from microbes. For this purpose, explants are treated with specific antimicrobial chemicals like mercury chloride, hydrogen peroxide, etc.
This procedure is called surface sterilisation. The vessels, media and instruments, are suitably treated with steam (in autoclave), dry heat or alcohol or subjected to filtration to make them free from microbes. This is complete sterilisation.

3. Preparation of Nutrient or Culture Medium
The medium on which explants are cultured is known nutrient medium or culture medium or simply medium. The culture media may be solid or liquid. The optimum pFl of the media should be 5.7.
The basic components of culture media are
(i) Inorgnic nutrients These include salts, providing all essential macro and microelements. Macronutrients include salts of calcium, magnesium, nitrogen, phosphorus and potassium. Micronutrients include iron, chloride, copper, zinc, boron and molybdenum.
(ii) Source of carbon These are the sources of energy in the form of sucrose, glucose, fructose or carbohydrates, amino acids, etc.
(iii) Growth hormones and vitamins Auxin (2, 4 -D) and cytokinins (benzyl amino purine), vitamins (Pyridoxine HCL) are commonly used in tissue culture. A media without growth hormones is known as base media. High auxins result in root formation while high cytokinins may yield shoots. After the preparation of medium, agar-agar is added in order to obtain a solid medium. In some cases liquid medium is required, for example in root culture where no agar-agar is added.

4. Inoculation
The process of transfer of explant to suitable nutrient medium contained in culture vessels is called inoculation. It is done under sterile conditions, achieved in an inoculation chamber or under laminar air flow. After the process, temperature and light of vessels is kept at controlled range. The temperature ranges between 18-25°C.

5. Callus Formation and its Culture
In callus culture, cell division in the explant forms a callus. It is an amorphous mass of’loosely arranged thin-walled parenchymatous cells developing frome proliferating cells of the parent tissue (Dodos and Roberts; 1985). This is usually maintained on a medium gelled with agar. If nutrient medium contains auxins cell division occurs and the upper surface of explant gets covered by callus. This callus later develops into normal roots, shoots and finally lead to the formation of plant. The development of callus occurs through three stages, i. e. induction, cell division and differentiation.

The callus formation is affected by the composition of medium, the source from which explant has been taken and the surrounding environmental factors. The first stage (induction) involves stimulation of metabolic rate of cells. With the increase in the metabolic rate, these cells enter the cell division stage. Finally in differentiation stage, the cells produce secondary products by the expression of certain metabolic pathways. It is necessary to subculture the callus in fresh media when the callus is being grbwn for a long time on the nutrient media.

6. Organogenesis
It involves the formation of plant organs, i.e. roots and shoots directly from cultured tissues. Organogenesis begins from the stimulation provided by the chemicals of medium, endogenous compounds produced by the culture and substances that have been carried over from the original explants. The process of formation of roots is known as rhizogenesis while that of shoots is caulogenesis. Organogenesis is highly controlled by the ‘ melatin concentrations of auxin and cytokinin in medium.

It was Skoog and Miller (1957) who demonstrated that a high concentration of auxin promotes rhizogenesis while high concentration of cytokinin promotes caulogenesis.

7. Somatic Embryogenesis
A Somatic Embryo (SE) is an embryo derived from a somatic cell, other than zygote. SEs are obtained usually on culture of the somatic cells in vitro. So, this process is called somatic embryogenesis. The embryo formed is known as embryoids. SEs are bipolar structures, i.e. they have a radicle and a plumule.

It is induced by a relatively high concentration of an auxin, like 2, 4-D. There are two different media for the formation of embryoids. The first medium comprises of auxin that initiates embryogenic cells.

The second medium either lacks or has decreased level of auxins. For the further development of embryonic cells into embryoids and plantlets the embryogenic cells undergo three developmental stages such as globular, heart-shaped and torpedo stage. Examples of plants undergoing embryogenesis in vitro include Nicotiana tabaccum, Loffea arabica, Atropa belladona, Brassica oleracea, etc.
The method used for tissue culture is as given below
Major Methodology of plant Tissue Culture
CHSE Odisha Class 12 Biology Solutions Chapter 10 Improvement in Food Production 3
Events of somatic embryogenesis

Question 4.
Elaborate the application of plant tissue culture.
Answer:
Applications of Plant Tissue Culture
(i) Micropropagation or Clonal Propagation:
By the process of plant tissue culture which requires lesser space and lesser time, a large population of plants could be raised. Also since the plants produced are genetically identical, this process is also called as clonal propagation. Examples of plants cutlivated micropropagation include grapes, bamboo, coffee, banana, cardamoms, etc.

(ii) Production of Virus-Free Plants:
Crop plants that reproduce asexually are susceptible to viral infections which advances through the vegetative organs for propagation like stem, tuber, rhizome, etc. The cambium culture in some plants produces virus-free plants.

(iii) Synthetic Seeds/Artificial Seeds:
Artificial seeds are those seeds in which somatic embryos or plantlets are encapsulated by calcium alginates. This can put a stop to desiccation and they could be used by farmers like normal seeds and are also used for rapid propagation of crop plants.

(iv) Embryo Rescue:
It is a technique in which immature embryos are dissected out from the fruit (seeds). They are then grown in nutrient medium which lead to the formation of plantlets. Embryo rescue technique is done in conditions where the embryo does not develop after initial divisions though the pollination and fertilisation had been successfully completed.
This technique is being used to improve chick-pea, groundnut, etc. at International Crop Research Institute for Semi Arid Tropics (ICRISAT), Hyderabad.

(v) Endosperm Culture:
It is used to produce triploids. Endosperm culture is helpful in producing seedless apple, Citrus which are of better commercial values.

(vi) Secondary Metabolites Production:
Cell suspension culture has been employed for commercial production of secondary metabolites like tannin, latex, resin. These cost of secondary metabolites production would be very high if manufactured chemically. So, the plant tissue culture comprising of large scale cell suspension culture has been used.

CHSE Odisha Class 12 Biology Solutions Chapter 9 Health and Diseases

July 21, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 9 Health and Diseases Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 9 Question Answer Health and Diseases

Health and Diseases Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Multiple choice questions

Question 1.
Which one of the following diseases are communicable ?
(a) Deficiency diseases
(b) Allergies
(c) Degenerative diseases
(d) Infectious diseases
Answer:
(d) Infectious diseases

Question 2.
The nature of the spread of communicable diseases is termed as
(a) parasitology
(b) immunology
(c) epidemiology
(d) None of these
Answer:
(c) epidemiology

Question 3.
Which one of the following is a sexually transmitted disease ?
(a) Q-fever
(b) Leprosy
(c) Whooping cough
(d) Gonorrhoea
Answer:
(d) Gonorrhoea

Question 4.
Gonorrhoea is a
(a) bacterial disease
(b) Veneral disease
(c) STD
(d) All of these
Answer:
(c) STD

Question 5.
Anthrax is caused by
(a) Vibrio
(b) Bacillus
(c) Salmonella
(d) virus
Answer:
(b) Bacillus

Question 6.
Some common diseases caused by bacteria are
(a) measles, mumps and malaria
(b) tetanus, typhoid and tuberculosis
(c) syphilis, smallpox and sleeping sickness
(d) pneumonia, poliomyelitis and psittacosis
Answer:
(b) tetanus, typhoid and mberculosis

Question 7.
Which one of the following disease is spread through wounds ?
(a) Tetanus
(b) Cholera
(c) Plague
(d) Tuberculosis
Answer:
(a) Tetanus

Question 8.
Which of the following is a bacterial disease ?
(a) Measles
(b) Smallpox
(c) Rabies
(d)Tuberculosis
Answer:
(d)Tuberculosis

Question 9.
Causative agent of TB is
(a) Salmonella
(b) Streptococcus
(c) Mycobacterium
(d) Pneumococcus
Ans.
(c) Mycobacterium

Question 10.
BCG vaccine is a preventive measure against
(a) Tuberculosis
(b) Typhoid
(c) AIDS
(d) Cholera
Ans.
(a) Tuberculosis

Question 11.
Which one is not a bacterial disease ?
(a) Tuberculosis
(b) Typhoid
(c) AIDS
(d) Cholera
Ans.
(c) AIDS

Question 12.
Mantoux test is for
(a) scarlet fever
(b) diptheria
(c) rheumatoid fever
(d) tuberculosis
Ans.
(d) tuberculosis

Question 13.
Chickenpox is caused by
(a) Varicella virus
(b) adenovirus
(c) SV-40 virus
(d) bacteriophage-T₂
Ans.
(a) Varicella virus

Question 14.
Smallpox is due to
(a) virus
(b) bacterium
(c) protozoan
(d) helminth
Ans.
(a) virus

Question 15.
The disease caused by virus is
(a) pneumonia
(b) tuberculosis
(c) smallpox
(d) typhoid
Ans.
(c) smallpox

Question 16.
Polio is caused by
(a) virus with double-stranded DNA
(b) virus with double-stranded RNA
(c) virus with single-stranded DNA
(d) virus with single-stranded RNA
Ans.
(d) virus with single-stranded RNA

Question 17.
Mumps is a
(a) protozoan disease
(b) viral disease
(c) fungal disease
(d) bacterial disease
Ans.
(b) viral disease

Question 18.
Which one is a viral disease ?
(a) Measles
(b) Rickets
(c) Syphilis
(d) Congenital night blindness
Answer:
(a) Measles

Question 19.
Amoebiasis is caused by
(a) Plasmodium vivax
(b) Entamoeba gingivalis
(c) Trypanosoma gambiense
(d) Entamoeba histolytica
Answer:
(d) Entamoeba histolytica

Question 20.
Entamoeba histolytica infection occurs through
(a) mosquito bite
(b) bird droppings
(c) sweat
(d) contaminated food and water
Answer:
(d) contaminated food and water

Question 21.
The infective stage of Entamoeba histolytica is
(a) binucleate form
(b) tetranucleate form
(c) minute form
(d) sporozoite stage
Answer:
(b) tetranucleate form

Question 22.
Malaria is transmitted by
(a) male Anopheles
(b) female Anopheles
(c) female Culex
(d) female Aedes
Answer:
(b) female Anopheles

Question 23.
Select the incorrect pair
(a) Pedicuius-Typhoid
(b) Xenopsylla-Plague
(c) Culex-Malaria
(d) Aedes-Yellow fever
Answer:
(a) Pedicuius-Typhoid

Question 24.
Filaria is transmitted by
(a) tse-tse fly
(b) sand fly
(c) Anopheles
(d) Culex
Answer:
(b) sand fly

Question 25.
Culex causes the disease
(a) malaria
(b) filariasis
(c) yellow fever
(d) sleeping sickness
Answer:
(b) filariasis

Question 26.
The disease elephantiasis is caused by
(a) Culex mosquito
(b) Anopheles mosquito
(c) housefly
(d) tse-tse fly
Answer:
(a) Culex mosquito

Question 27.
Microfilariae are found in the peripheral blood of man during
(a) day time
(b) day and night time
(c) night time
(d) None of the above
Answer:
(c) night time

Question 28.
Infection of Ascaris occurs due to
(a) tse-tse fly
(b) mosquito bite
(c) imperfectly cooked pork
(d) contaminated food and water
Answer:
(d) contaminated food and water

Question 29.
A disease caused by nematode parasite
(a) filariasis
(b) leprosy
(c) amoebiasis
(d) poliomyelitis
Answer:
(a) filariasis

Question 30.
AIDS is caused by
(a) HTLV-III
(b) herpes virus
(c) rotavirus
(d) orthomyxovirus
Answer:
(a) HTLV-III

Question 31.
Cerebral malaria is caused by Plasmodium
(a) vivax
(b) ovale
(c) falciparum
(d) All of these
Answer:
(c) falciparum

Question 32.
Which of the glands is often referred in relation with AIDS?
(a) Thyroid
(b) Adrenal
(c) Thymus
(d) Pancreas
Ans.
(c) Thymus

Question 33.
AIDS is caused by
(a) virus
(b) fungus
(c) helminth
(d) bacterium
Ans.
(a) virus

Question 34.
AIDS is due to
(a) reduction in number of helper T-cells
(b) lack of interferon
(c) reduction is number of killer T-cells
(d) auto-immunity
Answer:
(a) reduction in number of helper T-cells

Question 35.
AIDS virus has
(a) double-stranded DNA
(b) single-stranded DNA
(c) single-stranded RNA
(d) double-stranded RNA
Ans.
(c) single-stranded RNA

Question 36.
AIDS spreads through
(a) immoral way of life
(b) infected needles and syringes
(c) homosexuality
(d) All of the above
Ans.
(d) All of the above

Question 37.
Cancer is
(a) non-malignant tumour
(b) controlled division of cells
(c) unrestrained division of cells
(d) microbial infection
Ans.
(c) unrestrained division of cells

Question 38.
Cancer cells are damaged by radiations while others are not
(a) being different in nature
(b) being starved
(c) undergoing rapid division
(d) None of the above
Answer:
(c) undergoing rapid division

Question 39.
Sarcoma is the cancer of
(a) epithelial tissues
(b) connective tissues
(c) blood
(d) endodermal tissues
Answer:
(b) connective tissues

Question 40.
Blood cancer is called
(a) leukemia
(b) haemophilia
(c) thrombosis
(d) haemolysis
Answer:
(a) leukemia

Question 41.
The cells affected by leukemia are
(a) plasma cells
(b) erythrocytes
(c) thrombocytes
(d) leucocytes
Answer:
(a) plasma cells

Question 42.
Genes involved in cancer are
(a) tumour genes
(b) oncogenes
(c) cancer genes
(d) regulator genes
Answer:
(b) oncogenes

Question 43.
Oncology is the study of
(a) living cells
(b) cancer cells
(c) dead cells
(d) dividing cells
Answer:
(b) cancer cells

Question 44.
The most common cancer in women is
(a) breast cancer
(b) skin cancer
(c) cervix cancer
(d) leukemia
Answer:
(a) breast cancer

Question 45.
Breast cancer is an examle of
(a) adenoma
(b) lymphoma
(c) carcinoma
(d) sarcoma
Answer:
(c) carcinoma

Question 46.
Cancer treatment includes
(a) surgery
(b) radiotherapy
(c) treatment with anticancer drugs
(d) All of the above
Answer:
(d) All of the above

Question 47.
The most common type of cancer in man is
(a) skin cancer
(b) lung cancer
(c) cancer of prostate
(d) cancer of bladder
Answer:
(b) lung cancer

Question 48.
Which one of the following is a cancer causing agent ?
(a) Tobacco
(b) Radiation
(c) Smoking
(d) All of these
Answer:
(d) All of these

Question 49.
Which one of the following is an oncogenic virus ?
(a) Herpes simplex-II
(b) Papilloma
(c) Epstein-Barr
(d) All of these
Answer:
(c) Epstein-Barr

Question 50.
The spread of cancerous cells to distant sites is termed
(a) metamorphosis
(b) metagenesis
(c) metastasis
(d) metachrosis
Answer:
(c) metastasis

Question 51.
Adenoma refers to the cancer of
(a) glands
(b) lymph nodes
(c) blood
(d) muscles
Answer:
(a) glands

Question 52.
Which one of the following is an anticancer drug?
(a) Aspirin
(b) Flagyl
(c) Streptomycin
(d) Vincristine
Answer:
(d) Vincristine

Question 53.
Which of the following scientists got Noble prize in 1989 for the studies on the genetic basis of cancer ?
(a) Philip Sharp and Richard Roberts
(b) David Baltimore and Howard Temin
(c) Michael Bishop and Harold Varmus
(d) Stanley B Prusiner
Answer:
(c) Michael Bishop and Harold Varmus

Question 54.
HIV attacks which one of the following ?
(a) B-cells
(b) T- cells
(c) Antigen preventing cell
(d) T-helper cells
Answer:
(d) T-helper cells

Question 55.
Which one of the following is not a component of innate immunity ?
(a) Antibodies
(b) Interferons
(c) Complement proteins
(d) Phagocytes
Answer:
(a) Antibodies

Question 56.
Which of the following is involved in defense mechanism of the body ?
(a) Lymphocytes
(b) Neutrophils
(c) Macrophages
(d) All of these
Answer:
(d) All of these

Question 57.
During allergic reactions, which of the following is secreted ?
(a) Allergens
(b) Histamines
(c) Immunoglobulins
(d) Pyrogens
Answer:
(b) Histamines

Question 58.
Immunoglobulins are
(a) antigen
(b) antibodies
(c) antiseptics
(d) antibiotics
Answer:
(b) antibodies

Question 59.
B-lymphocytes are produced by
(a) liver
(b) thymus
(c) spleen
(d) bone marrow
Answer:
(d) bone marrow

Question 60.
Cell-mediated immunity is due to
(a) B-cells
(b) T-cells
(c) T-helper cells
(d) All of these
Answer:
(b) T-cells

Question 61.
The cells which release the antibodies are
(a) helper T- cells
(b) B-cells
(c) plasma cells
(d) T-cells
Answer:
(b) B-cells

Question 62.
Antiviral substances are
(a) antibodies
(b) antibiotics
(c) interferons
(d) vaccines
Answer:
(c) interferons

Question 63.
The major phagocytic cells are
(a) lymphocytes
(b) mast cells
(c) macrophages
(d) plasma cells
Answer:
(c) macrophages

Question 64.
Which immunoglobulin is the largest in size ?
(a) IgA
(b) IgD
(c) IgE
(d) IgM
Answer:
(d) IgM

Question 65.
Vaccine for rabies was first produced by
(a) Louis Pasteur
(b) Edward Jenner
(c) Paul Berg
(d) None of these
Answer:
(a) Louis Pasteur

Question 66.
Vaccination means introduction in our body of
(a) weakened germs
(b) WBCs from other animals
(c) antibodies
(d) All of the above
Answer:
(a) weakened germs

Question 67.
The biochemical basis of vaccination was given by
(a) Louis Pasteur
(b) Salk
(c) Kohler
(d) Edward Jenner
Answer:
(d) Edward Jenner

Question 68.
Against which foreign organism (antigen) antibiotic is effective?
(a) Virus
(b) Bacteria
(c) Fungal infection
(d) Protozoan
Answer:
(b) Bacteria

Fill in the blanks

Question 1.
The immunity, present right from birth is known as ………….. immunity.
Answer:
innate

Question 2.
The immunity generated on exposure to foreign antigens is known as ………… immunity.
Answer:
acquired

Question 3.
Anti Tetanus Serum (ATS) administration generates ……….. immunity in the body.
Answer:
artificial passive

Question 4.
Toxoid is an example of ………. immunity.
Answer:
adaptive

Question 5.
A part of an antigen that evokes an immune response is called antigen …………
Answer:
determinant (epitope)

Question 6.
Antibodies segregate with ………. class of serum proteins.
Answer:
immunogens

Question 7.
The stem of the ‘Y’-shaped immunoglobulin molecule carries out …………. functions.
Answer:
effector

Question 8.
Among all immunoglobulins ………… can cross the placental barrier.
Answer:
IgM

Question 9.
During primary immune response, ………… immunoglobulin is predominant.
Answer:
IgG

Question 10.
Immunoglobulin ……………. is present in the mother’s milk, tear and saliva.
Answer:
IgA

Question 11.
Formation of antibodies against self antigens leads to an ………… disorder.
Answer:
autoimmune

Question 12.
……………… released by mast cells causes inflammatory response.
Answer:
Histamine

Question 13.
Humans get AIDS virus from
Answer:
HIV contaminated needle

Question 14.
The tests conducted for determining AIDS and typhoid are test and test respectively.
Answer:
ELISA, Widal

Answer the following in one or a few sentences

Question 1.
What is passive acquired immunity ? Explain.
Answer:
It is the immunity which is acquired by readymade antibodies or sensitised WBC directly injected to a person. It provides immediate relief and is not long lasting. It is classified as
• Natural passive acquired immunity
• Artificial passive acquired immunity

Question 2.
What is an antigenic determinant (epitope)?
Answer:
Epitope is the component or an active site of an antigen which binds to the complementary past of an antibody called paratope. It is also known as antigenic determinant.

Question 3.
Explain humoral immunity.
Answer:
The immunity which is mediated by antibodies present in blood and lymph is known as humoral immunity or immune response.

Question 4.
Explain about the antigen binding sites of an antibody.
Answer:
‘Y’-shaped antibody molecule possesses antigen-binding sites and are known as Fragment antigen binding (Fab). This site has the ability to recognise a complementary antigen and bind to it.

Question 5.
Mention about the effector functions of an antibody.
Answer:
Antibodies have several mechanisms by which they act in body. To combat pathogens which are replicated outside cells, antibodies binds to pathogens to link them together.
It causes them to agglutinate. So, by coating the pathogen, antibodies stimulate effector functions against pathogen.

Question 6.
How do antigens interact with their antibodies?
Answer:
Antigen-Antibody Interaction:
Antigens or immunogens are whole organisms or foreign particles that can evoke immune responses and can bind to antibodies in a specific manner. An antibody interacts with the small specific part of an antigen, called epitope or antigenic determinant. Epitope is the immunologically specific component or active site of an antigen, which hinds to the complementary part of an antibody called paratope.

Question 7.
What is a toxoid ? Name the bacterial diseases against which toxoids are used as vaccines.
Answer:
Some pathogenic bacteria producess exotoxins which are isolated and chemically modified to reduce their toxicity. Such exotoxins are non-toxic immunogenic deterivatives also called as toxoids. Diphtheria and tetanus vaccines are produced from toxoids and treat bacterial diseases.

Question 8.
What is an oral polio vaccine?
Answer:
Polio is an infectious disease caused by a virus. Oral Polio Vaccine or OPV are the predominant vaccine used to eradicate polio. Oral polio vaccine results in vaccine associated paralytic polio.

Question 9.
What is immunosuppression?
Answer:
The reduction of activation of immune system is called immuno suppression. It can either be deliberate or as an adverse effect of any therapeutic agent. The major causes of immunosuppression are diabetes, chronic alcoholism, renal failure, autoimmune disorders or CNS infection.

Question 10.
Explain autoimmune haemolytic anaemia.
Answer:
The condition in which antibodies of a person target their own blood cells and cause them to burst, leading to an insufficient oxygen carrying blood cells in the circulatory system, is called Autoimmune Haemolytic Anaemia (AIHA).

Question 11.
What is an immune deficiency?
Answer:
The state in which immune system’s ability to fight diseases is negligible or completely absent is called immunodeficiency. It usually occurs as a result of extrinsic factors which includes HIV infection, extremes of age or environmental factors.

Question 12.
Explain reticular dysgenesis.
Answer:
Reticular Dysgenesis (RD ) is a rare inherited autosomal recessive disease that results in immune deficiency. A weakened immune system leave patients susceptible to different kinds of infections.

Short Answer Type Questions

Question 1.
What is the causative organism of filariasis and write a note on its prevention and control.
Answer:
The causative organism of filariasis is Wuchereria bancrofii and Wuchereria malayi and Culex mosquito is the vector. Anti-mosquito measures are taken to eliminate the breeding places for the vectors which causes filariasis and also helps to control the spread.

Question 2.
Write the names of five drugs to control malaria.
Answer:
The drugs which helps to control malaria.
(i) Chloroquine
(ii) Doxycycline
(iii) Resochins
(iv) Paludrine
(v) Daraprim

Question 3.
What are the different species of malarial parasite?
Answer:
Malaria is caused by potozoan parasite Plasmodium. The four different species which cause malaria in humans

P. falciparum
P. ovale
P. malarial
P. vivax

Question 4.
What are the causes of non-communicable diseases?
Answer:
The major causes for the occurrence of non-communicable diseases are

Air-borne germs These are spread through air to a healthy individuals. Common diseases which spread through air-borne germs are measles, tuberculosis and chicken pox.
Direct/ indirect contact With a person suffering from communicable diseases can cause the spread.
Food borne/water borne The disease can also be caused by sharing food or water with infected person.

Question 5.
What are the measures taken to control malaria?
Answer:
Control Malaria:
In 1979, WHO expert committee summarised few antimalarial measures. These are

Use of mosquito repellents, bed-nets and cleaning of houses.
Use of aerosols near domestic area.
Destroy mosquito larvae by larvicides by using larvivorous fishes like Gambusia.
Manage water fills and digs to prevent the area from the development of larvae.
Chemoprophylaxis or little dose of quinine to be administered in malaria prone area.
Chemotherapy in which medicines like quinine, paluidine, camoquin, resochin, mepacrine, lavagnin, daraprin, etc., are given to people to prevent them from malarial infection.

Question 6.
Write a short note on tumour and their types.
Answer:
It involves the following common methods

Surgery In this primary approach, tumours are removed by surgery to check further spread of cancer cells.
Radiotherapy In this technique, tumour cells are irradiated by lethal doses of radiation by protecting the surrounding normal cells.
Chemotherapy In this several chemotherapeutic drugs are used to kill cancer cells. But their side effects like hair loss, anaemia are also reported.
Immunotherapy In this process of treatment, several biological modifiers like a-interferons are used to activate the immune system and help in destroying the tumour.

Question 7.
What is ascariasis and how it is controlled?
Answer:
Ascariasis:
It is caused by an intestinal endoparasite of human, i.e. Ascaris lumbricoides commonly known as roundworm. It is the most common nematode parasite that occurs worldwide and mostly found in tropical and subtropical areas where hygiene and sanitation are poor. The adult female is about 12 inches in length while male adults are smaller.

Infection is more common in rural areas of South-Eastern part in India. Children get more affected than adults by this disease due to poor sanitation habits.

Control:
Few preventive measures are given below

Maintain personal hygiene.
Consume thoroughly washed and properly cooked vegetables and fruits.
Drink packaged or boiled water.
Disposal of fecal matter away from habitation crops and water sources.
Do not let children to play in soil.

Question 8.
Write a short note on amoebiasis.
Answer:
It is caused by Entamoeba histolytica which is found inside or outside the intestine. The symptoms of intestinal amoebiasis are amoebic dysentry, non-dysentric colitis, amoeboma and amoebic appendicitis leading to complications like intestinal perforation, peritonitis and haemorrhage. The extra-intestinal amoebiasis can also occur in liver, lungs, brain, spleen and skin. The most common type of amoebiasis is hepatic amoebiasis.
E. histolytica is a monogenetic parasite and its only host is human.

Question 9.
What is AIDS? How can it be prevented?
Answer:
AIDS or Acquired Immuno Deficiency Syndrome refers to a disorder in which the immunity of body is decreased due to reduction of T-helper cells that activate other lymphocytes too.
It’s caused due HIV or Human Immuno Deficiency virus.

Prevention of AIDS

Sterlise all surgical instruments before use.
The transfusion of blood should be subjected to HIV test.
Infected mother should avoid pregnancy otherwise, it may also transmit to child.
Heterosexual activites should be prohibited.
Motivate to use condoms during sexual activities.
Proper medical dispose off should be established.

Question 10.
What is diabetes mellitus ? How can it be controlled ?
Answer:
The increased level of blood sugar in human body due to hyposecretion of insulin hormone leads to a condition called hyperglycemia. Prolonged hyperglycemia leads to diabetes mellitus characterised by high sugar, weight loss and production of excess urine. It is an acquired non-communicable disease of humans.
Diabetes can be kept under control by changing the diet to sugar free, administration of insulin hormone through injections, etc.

Question 11.
What are carcinogen?
Answer:
Causes of Cancer:
The agents which cause cancer, are called carcinogens.
Cancer can be induced by either physical, chemical or biological agents.

Physical agents These are ionising radiations like X-rays, Y-rays and the non-ionising rays like UV-rays which can cause DNA damage leading to neoplastic transformation.
Chemical agents These are tobacco smoke, benzene fumes, arsenic, hormones and aflatoxin, etc.
Nutritional agents Deficiency of some nutrients like vitamins, minerals and proteins causes cancer.
Biological agents Many cancers are caused by viruses. The association of Hepatitis-B and primary liver cancer has been established.
Mechanical factors Trauma, irritation and severe friction have been identified to cause malignancy.
Host factors These include age, sex, marital status, race, socio-economic status, customs and habits of the host.
Environmental factors These include radiation, air pollution, diet, drugs and social environment.
Genetic factors All factors have a genetic basis and are caused by genetic transformations of cells.

Question 12.
What STDs stand for? Explain with examples.
Answer:
STD stands for sexually transmitted diseases, which are transmitted through sexual intercourse with infected persons. For example AIDS, syphilis, trichomoniasis.

Syphilis is caused by bacteria named Treponema pallidum. Initially, it leads to ulcers on the genitalia followed by skin lesions, rashes and swollen joints.
It is cured by taking penicillin or tetracycline as antibiotics.
AIDS is caused by human immunodeficiency virus. It leads to decreased immunity of the patient along with many other symptoms like lethargy, weight loss, nausea, fiver. Although, AIDS is incurable yet a drug zidovudine (AZT) is used to treat this.
Trichomoniasis is a STD caused by Protozoa Trichomonas vaginalis. It infects both male and female causing foul smelling, yellow discharge and burning sensation in females and pain and burning sensation in males. It is usually treated by metronidazole in both the cases.

Question 13.
What is cancer? Give its causes.
Answer:
It is defined as an uncontrolled growth or proliferation of cells without any differentiation. Cancer cells divide repeatedly in an uncontrolled manner. It has an ability to invade other tissues or organs, cause necrosis or programmed cell death, i.e. apoptosis.

In normal cells, cell growth and differentiation is highly controlled and regulated. Normal cell shows a property called contact inhibition by virtue of which contact with other cells stops their uncontrolled growth. Cancerous cells appear to have lost this property. As a result, these cells continue to divide to produce a mass of cells called tumour or neoplasm.

Causes of Cancer
The agents which cause cancer, are called carcinogens.
Cancer can be induced by either physical, chemical or biological agents.

Physical agents These are ionising radiations like X-rays, v-rays and the non-ionising rays like UV-rays which can cause DNA damage leading to neoplastic transformation.
Chemical agents These are tobacco smoke, benzene fumes, arsenic, hormones and aflatoxin, etc.
Nutritional agents Deficiency of some nutrients like vitamins, minerals and proteins causes cancer.
Biological agents Many cancers are caused by viruses. The association of Hepatitis-B and primary liver cancer has been established.
Mechanical factors Trauma, irritation and severe friction have been identified to cause malignancy.
Host factors These include age, sex, marital status, race, socio-economic status, customs and habits of the host.
Environmental factors These include radiation, air pollution, diet, drugs and social environment.
Genetic factors All factors have a genetic basis and are caused by genetic transformations of cells.

Question 14.
Write down different types of cancer.
Answer:
Types of Cancer
On the basis of localisation, cancer is divided into several main types

Carcinoma Cancer of epithelial tissues and their derivatives, e.g. breast cancer, lung cancer.
Sarcoma Cancer of connective tissues, e.g. bone cancer, muscle cancer, cancer of lymph nodes.
Lymphoma Excessive production of lymphocytes by lymph nodes and spleen, e.g. Hodgkins disease, multiple myeloma and other immunoproliferative diseases.
Leukemia Cancer of blood forming tissues like stem cells in bone marrow. There is increase in WBC number which destroys the cells of other organs, commonly known as blood cancer.

Some Other Types of Cancer

Adenoma Cancer of glands.
Lipoma Cancer of adipose tissue.
Glioma Cancer of glial cells of central nervous system.
Myoma Cancer of muscular tissue.
Melanoma Cancer of pigmented epithelium of skin.

Question 15.
What is the causative agent of gonorrhoea? What are its symptoms and treatment?
Answer:
Gonorrhoea is caused by bacteria Neisseria gonorrhoea. It resides in the genital tube and produces pus-containing discharge, pain around genitalia and burning sensation during urination. It can be cured through appropriate medicines like penicillin or ampicillin.

Question 16.
Explain oncogenes.
Answer:
Oncogenes encode oncoproteins which promote the loss of growth control and the transformation of cell to a malignant cells. Cancer causing viruses are called oncoviruses and their genes as v-onc (viral protooncogenes). These viral oncogenes have homologous regions in human genome.

The homologous genes are called cellular protooncogenes (c-onc). Nearly 100 protooncogenes are known and these are involved in cell functions. The sudden-change, i.e. mutation in protooncogenes induces abnormal functioning and tumour formation.
Viral protooncogenes constitutes another class of factors transforming protooncogenes into expression ready cellular oncogenes. Which encodes for abnormal proteins known as oncoproteins.
The name of oncogenes are derived from the names of the host viruses are v-src, c-myc, etc.

Question 17.
Explain tumour suppressor gene or antioncogene.
Answer:
Tumor suppressor gene or antioncogene are the genes which protects a cell form the formation of cancerous cells.
When these genes are characterised by mutations, it leads to reduction in its function and cell becomes prone to cancer along with many genetic changes. Tumor suppressor genes are categorised into caretaker gatekeeper and landscaper genes.

Question 18.
Write a note on parasite.
Answer:
Parasite are the organism which lives on other organisms called host and derive their nutrition from the host. They are dependent on host for their survival and they have to be in host, to live, grow and multiply. The one which lives on the surfaces of earth are called ectoparasite, while which lives in the organisms are called endoparasites.

Question 19.
Explain incubation period of malaria parasite.
Answer:
The incubation period in malaria is defined as the period between infection and beginning of the symptoms. It typically lasts between 10 days to 4 weeks.
The incubation period is affected by the type of Plasmodium parasite responsible for the infection. If a patient is given antimalarial drugs which prevent the spread of disease, it can also increase the incubation period by weeks or months.

Question 20.
What kind of physical changes are characteristic of adolescence?
Answer:
Physical changes Adolescence is a period of active growth and sexual maturity. Growth becomes once apparent with an increase in body size, height and weight due to continued secretion of growth and sex hormones (FGH and LH).

Under the influence of these hormones, the body begins to develop secondary sexual characters in males like beard growth, change in voice pitch, etc., and females such as initiation of menstruation, enhanced breast size, etc.

Question 21.
What kind of psychological changes characterise adolescence?
Answer:
Psychological changes Adolescence shows changes in behaviour, emotions and attitude.
For example, difficulty in accepting parental decisions, coping with studies, competition, increased need for money, keeping bad company, etc.

Question 22.
Which is the most common skin problem that affects the youth in adolescence? What are its causes ?
Answer:
The most common skin problem that occurs during youth or teen years is acne.
During puberty hormone level increases and the skin starts releasing more oil (sebum). When this mixes with dead cells of the skin, it closes the pores and causes swelling, redness and pus.
Few medical conditions such as polycystic ovary syndrome, cushing’s syndrome can also lead to acne.

Question 23.
What is the cause of alcoholism?
Answer:
The dependence on alcohol or when a person becomes addicted to alcohol is called alcoholism. It is a result of combination of genetic, psychological, environmental and social factors described below

People become addicted to alcohol to relieve stress and the deal with the pressure in their families or workplace.
Disorders like anxiety, depression, bipolars disorders or other medical issue can increase the risk of alcoholism.

Question 24.
What are the effects of alcoholism in the body?
Answer:
Effects of Alcohol

High dose of alcohol, i.e. more than 30 ml acts as an intoxicant and affects the functioning of CNS.
Alcoholism damages internal organs like liver, as alcohol is converted to acetaldehyde then to fat in liver. This fat begins to deposit in body and cause cirrhosis.
It many also cause hepatitis and liver cancer.
Increased consumption of alcohol per day dilates the blood vessels and it leads to hardening of blood vessels. This causes bradycardia and myocardiopathy.
Alcohol decreases ADH secretion and this may cause dehydration.
Drinking alcohol makes the person unusually aggressive and also, affects this judgement, coordination, alterness, vision and responsiveness.
Excessive intake of alcohol affects the behaviour of an individual.

Question 25.
What are the moral and social implications of drinking?
Answer:
Social and Moral Implications of Addiction

Habitual drinking creates differences in the family. The addict cause public misdemeanour and misbehave hence is isolated from society as drinking is considered a social evil.
Family status declines due to approaching poverty.
Such individuals become violent suicidal, antisocial and- lazy.
Drug and alcohol addicts develop habits like stealing, burrowing money for fulfilling their addiction.

Question 26.
What are the reasons of drug abuse by the youth?
Or
Mention the causes of drug abuse.
Answer:
Serious effects of drug abuse are

Academic performance decreases.
Frequent absence from school or college.
Isolation, fatigue, depression and aggressiveness occurs in behaviour.
No coordination with family members and friends.
Frequent fluctuations in weight.
Intravenous drug intake leads to risk of AIDS and hepatitis-B.
Excess use of alcohol or drug damages the nervous system and causes liver cirrhosis or cancer.
During pregnancy in females, drugs affect foetus seriously.

Question 27.
Write briefly on the main classes of drugs in use.
Answer:
Drugs are placed into one of three classes A, B or C under the misuse of drugs act 1971.
A drug class is the set of similar action placed under same group.
Class-A includes heroin (diamorphine), cocaine, methadone, LSD, ecstasy and magic mushrooms.
Class-B includes amphetamines, barbiturates, codeine, cannabis, cathinones and synthetic cannabiroids.
Class-C includes benzodiazepines (transquilisers), ketamine, anabolic steroids and Benzylpiperazines (BZP).

Question 28.
What are the withdrawal symptoms that are seen after drug abuse?
Answer:
The withdrawal symptoms of alcohol and,drug abuse are-

Hallucination
Fits
Tremors

The treatment of drug abuse includes

Use of detoxifying drugs like diazepan, vitamin-B, chlordizepoxide, apomorphine.
Use of antioxidants like disulfiram, cephalosporin, metronidazole.

Question 29.
What are the social and moral implications of drug abuse?
Answer:
Social and Moral Implications of Addiction

Habitual drinking creates differences in the family. The addict cause public misdemeanour and misbehave hence is isolated from society as drinking is considered a social evil.
Family status declines due to approaching poverty.
Such individuals become violent suicidal, antisocial and- lazy.
Drug and alcohol addicts develop habits like stealing, burrowing money for fulfilling their addiction.

Question 30.
What are the effects of tobacco use in the body?
Answer:
Dried and crushed leaves of Nicotiana tabacum and Nicotiana rustica are used to make tobacco. It can induce lung cancer, bronchitis, emphysema, coronary heart disease, cancer of throat, oral cancer, cancer of urinary bladder, etc.
Smoking leads to the increase in the content of carbon monoxide in the blood which reduces the concentration of haemoglobin bound oxygen. This leads to oxygen deficiency in the body

Question 31.
What kind of diseases affect the body in smoking?
Answer:
Major diseases which affect the body in smoking are

Stroke As smoking affects the arteries of a person, it can trigger stroke.
Lung cancer It is the most common type of cancer caused due to smoking.
Chronic obstructive pulmonary disease It is an obstructive lung disease which leads to difficulty in breathing. It leads to early death.
Asthma Smoking irritates air passages and can trigger sudden and severe asthma attacks.
Cancer Over ten other types of cancer including colon, liver, cervix, stomach and pancreas are caused due to smoking.

Question 32.
What is mental illness?
Answer:
Mental illness is a state of emotional and psychological well being of a person which allows him/her to attain his/ her physical cognitive and emotional capabilities.

Question 33.
What are the causes of mental illness?
Answer:
The causes of mental illness are depression, obsessive, compulsive disorder, mood disorder, attention deficiency disorder, sleeplessness, self destructive actions, loss of memory, etc.

Question 34.
What are the different types of mental disorders seen in man?
Answer:
The different types of mental disorders are

Psychosis
Neurosis
Schizophrenia
Phobia
Epilepsy
Parkinson’s disease
Alzhaimer’s disease.

Differentiate between the following

Question 1.
Amoeba and Entamoeba.
Answer:
Differences between Amoeba and Entamoeba are as follows

Amoeba	Entamoeba
Amoeba are a large class of unicellular organisms that are eukaryotic.	Entamoeba are a genus of amoeba that live on other organisms.
They move by means of pseudopodia.	They are usually a part of normal fauna and live in symbiotic association.

Question 2.
Filaria and Malaria.
Answer:
Differences between filaria and malaria are as follows

Filaria	Malaria
It is a parasitic disease caused by infection of roundworms.	Malaria is caused by parasitic protozoan to Plasmodium.
The symptom includes edema which causes thickening of skin and underlying tissues.	The symptoms include headache, fever, joint pain, retinal damage, etc.
Wuchereria bancrofti is the parasite which causes filariasis.	Female Anopheles mosquito transmits a mature infective form to the host.

Question 3.
Communicable Diseases And Non-Communicable Diseases
Answer:
Differences between communicable diseases and non-communicable diseases are as follows

Communicable diseases	Non-communicable diseases
These disease do not remain confined to the person who suffer from them.	These disease remain confined to the person who suffer from them.
These are transmitted from infected person to other persons directly or indirectly by any causative organisms.	They are not transmitted from infected person to other persons except for genetic transmission in some case.
e.g. viral diseases (influenza, mumps, AIDS, smallpox) bacterial diseases (cholera,typhoid, TB,tetanus,etc.)	e.g, diabetes, cancer, arthritis, cardiovascular diseases, etc.

Question 4.
Magna and Minuta stage.
Answer:
Differences between magna stage and minuta stage are as follows

Magna stage	Minuta stage
It is the active stage of pathogenic stage of Entamoeba histolytica also called trophozoite.	It is the non-pathogenic and non-motile and non-feeding form.
It resembles Amoeba in its active form and cytoplasm is divisible into ectoplasm and endoplasm.	It lives in the lumen of intestine and may develop into magna by penetrating intestinal wall.
It measures 20-30 p in diameter.	It measures about 12-15 pt in diameter.

Question 5.
Infection and Infestation.
Answer:
Differences between infection and infestation are as follows

Infection	Infestation
Infection is caused by microorganisms or germs or viruses.	Infestation refers to the infection by larger and more complete organisms like pests or parasites.
The germs or microorganisms which causes infection usually grow inside the body and cause illness.	Infestation is commonly used in context to one organism present on external surface.

Question 6.
Carcinoma and Sarcoma.
Answer:
Differences between carcinoma and sarcoma are as follows

Carcinoma	Sarcoma
The cancer of epithelial epidermal tissues and their derivatives.	The cancer of connective tissues is called sarcoma.
It usually includes cancer of lungs, breast, etc.	It includes bone, muscle or cancer of lymph nodes.
They spread throughout the body by blood and lymph.	They spread through nodules.
They occur primarily in people over 50 years of age.	It affects both young and old people.

Question 7.
Benign tumour and Malignant tumour.
Answer:
Differences between benign tumour and malignant tumour are as follows

Benign tumour	Malignant tumour
It remain confined to the site of its origin.	It is not confined to the tissues.
It may grow in size but does not spread to other parts of the body.	They are carried to other parts of the body by blood or lymph.
It is enclosed in connective tissue.	It is not enclosed in any specific tissue.

Question 8.
Sporogony and Gamogony.
Answer:
Differences between sporogony and gamogony are as follows

Sporogony	Gamogony
It is an asexual stage which produces haploid sporozoites.	It is a sexual phase followed by sporogony which produces a diploid zygote.
The oocyte so formed are liberated into haemolymph of mosquito.	The zygote elongates into motile worm-like vermicule which penetrates the stomach wall, enclosed itself in a cyst and grows in size.

Question 9.
Innate immunity and Acquired immunity.
Answer:

Innate immunity	Acquired immunity
It is a non-specific type of immunity.	It is a pathogen specific immune response.
It is inherited from parents and protects the child since birth.	It is acquired after the birth of an individual, during its lifetime.
It provides barrier against the entry of pathogen in the body.	It produce B-lymphocytes and T-lymphocytes. It also produces primary and secondary types of immune response.

Question 10.
Cell-mediated immunity and Humoral immunity.
Answer:
Differences between cell-mediated immunity and humoral immunity are as follows

Cell-mediated immunity	Humoral immunity
It is the type of immunity which is mediated by T-lymphocytes to produce antibodies.	It is mediated by antibodies present in blood and lymph.
It provides immunity against all pathogens including fungi and Protozoa.	It provides immunity against virus and bacteria.
It shows reaction against organ transplantation.	It does not react against organ transplantation.

Question 11.
Vaccination and Immunisation.
Answer:
Differences between vaccination and immunisation are as follows

Vaccination	Immunisation
Vaccination is the process of introducing the body to a form of virus.	Immunisation is the process of body building up natural defence against bacteria.
It is injected in the form of drops.	It does not require administering as its the natural capacity of body.

Long Answer Type Questions

Question 1.
What are pathogens ? Classify diseases and give a note on this.
Answer:
Pathogens:
Infectious disease causing agents are called pathogens and their disease causing capacity is known as pathogenicity or virulence. Most of the pathogens are parasites. They can cause harm to the organism (host) by either living in (as endoparasites) or on them (as ectoparasite). These disrupt the normal physiology of organisms, either plants or animals and express a number of symptoms. The human body contains many natural defence mechanisms against some common pathogens. Certain pathogens have been found to be responsible for massive casualities.

Despite many medical advances for safeguarding human beings from infections by pathogens through the use of vaccines, antibiotics and fungicides, pathogens continue to threaten human lives. They can enter our body by various means s.uch as air, water, food, etc., and can multiply and interfere with the normal vital activities of the body, thus, resulting in the morphological and functional damage.

Classification of Pathogens:
Major classes of pathogens which cause disease, produce toxin and induce immunosuppression in the most are given below

Classes of Pathogens	Examples
Viruses	Adenovirus, picorna virus, retrovirus, papovavirus, polyma virus, etc.
Bacteria	Mycobacterium, Streptococcus, Shigella and Salmonella.
Fungi	Saprophytic pathogenic fungi.
Prions	Protein pathogens that cannot contain nucleic acids.
Parasites	Protozoan and helminth parasites.

Question 2.
Give the symptoms, infection, prevention and control of typhoid.
Answer:
Typhoid:
It is also known as enteric fever and is caused by bacterium Salmonella typhi. It is common in developing countries, where it affects 21.5 million persons every year (1 million in India).

Symptoms and Diagnosis
The incubation period of parasite is about 1-2 weeks and the duration of illness is about 4-6 weeks. The symptoms of typhoid include fever (39-40°C), lethargy, stomach pain, headache, poor appetite, diarrhoea or constipation and rose spots on abdomen. The intestinal
perforation or bleeding may occur in severe cases, which may lead to death. The reccurrence (relapsing) of disease is observed in 10% of patients. Typhoid is diagnosed by WIDAL test. ”

Infection and Transmission
Salmonella typhi invades human intestine through contaminated water or food, from where they are carried by white blood cells to the liver, spleen and bone marrow. They multiply in these organs and re-enter the bloodstream. At this stage, a person begins to develop symptoms like fever. Through the bloodstream the bacteria further invade various organs like gall bladder, biliary system, lymphatic tissues and ultimately pass into the intestinal tract. From here the bacteria can be diagnosed in cultures of stool.
The disease may be transmitted through carriers also. These are those person who recovered from typhoid but continue to carry the bacterial infection.

Treatment
Treatment includes antibiotics like fluoroquinolones, ceftriaxone and azithromycin. But, Salmonella develops resistance to multiple antibiotics. The emergence of multi-drug resistant typhoid has complicated the treatment procedure, especially in those who have acquired infection from South Asia. Therefore, antibiotic susceptibility test in helpful in deciding an appropriate therapy pathway.

Vaccination
The following vaccines are given in the treatment of typhoid

Vaccine	Type	Dose
Vi antigen	Inactivated vaccine injectable	A single dose of 0.5 ml administered intramuscularly on thighs and arms.
Oral ty21a	Oral live vaccine	Course of 3 capsules given on alternate days.

Prevention and Control
There are several ways through which bacterial infection of typhoid can be avoided

Maintain personal hygiene.
Consume thoroughly washed and properly cooked vegetables and fruits.
Drink packaged water with statutory quality or boiled water. Bottled carbonated water is also used to consume and it is safer than other.
Vaccination against typhoid can be done.

Question 4.
What are acquired and innate immunity?
Discuss the mechanical and chemical barriers of innate immunity.
Answer:
Innate Immunity (Inborn)
It is the type of immunity which is present from birth and is inherited from the parents. That’s why it is also called as natural immunity. It is non-specific in nature as it involves general protective measures against any invasion. Innate immunity provides the early lines of defense against pathogens. The principal components of innate immunity that act as barrier system to prevent the entry of pathogens are given below
1. Mechanical barriers
2. Chemical barriers
3. Phagocytosis
4. Fever
5. Inflammation
6. Acute phase proteins
7. Natural Killer (NK) cells

1. Mechanical or Physical Barriers:
They prevent entry of microorganisms in the body, e.g. skin, mucous coating of epithelium lining the respiratory, gastrointestinal and urogenital tracts. These barriers are also called as first line of defence.

Skin It is outer and tough layer of epidermis that consists of insoluble protein called keratin. It prevents the entry of bacteria and viruses. The periodical sheding off process of skin removes any clinging pathogen.
Mucous membrane The gastrointestinal tract, urinogenital tract and conjuctiva are lined by mucous membrane.

This membrane secretes mucus which entraps microbes, dust or any foreign particles and finally propelled them out through tears, saliva, coughing and sneezing.

2. Chemical or Physiological Barriers
It includes certain chemicals which dispose off the pathogens.
These are given below

Acid of stomach, kills the ingested microorganisms by secreting acid gastric secretion (pH 1.5 – 2.0).
Low pH of sebum (i.e. 3.0-5.0) forms a protective film over the skin that inhibits growth of many microbes.
Lysozyme is a hydrolytic enzyme present in all mucous secretions like tears, saliva and nasal secretions. It attacks bacteria and dissolves their cell walls.
Gastro and duodenal enzymes secrete proteases and lipases. These enzymes digest a variety of structural and chemical constituents of pathogens, e.g. gastric acids easily inactivate rhinoviruses.
Mothers milk Lactoferrin and neuraminic acid are antibacterial substances present in human milk to fight against Staphylococci.
A group of proteins produced by virus infected cells, i.e. interferons induces a generalised activated state in neighbouring uninfected cells.
Humans and some other animals secrete an number of antimicrobial peptides such as defensins. One micrometre thick biofilm of defensins protects the skin from microbial assault.

3. Phagocytosis
When pathogens or microbes penetrate the skin or mucous membrane certain cell types surge towards the site of infection. These can be neutrophils, monocytes and macrophages which engulf the pathogens to form a large intracellular vesicle called phagosome.
The phagosome fuses with lysosome to form phagolysosome. The secretion of lysosomal enzymes digests bacterial cells. The useful products remains in the cell while the waste is egested out of the cell. Therefore, these phagocytes are also known as second line of defence.

4. Fever
It may be brought about by endotoxins or proteins (cytokines) produce by pathogens called endogenous pyrogens.
When enough pyrogens are produced, then there is rise in temperature which strengthens the defence mechanism to inhibit the growth of microbes. Fever is a symptom of an internal diagnoses of the cause of infections.

5. Inflammation
It is a defensive response of the body to tissue damage.
It is characterised by abrasions, chemical irritations, heat, swelling, redness and pain. Inflammation in a non-specific response of the body to injury. It is an attempt to dispose off microbes, toxins or foreign material at the site of injury by macrophages to prevent their spread to other tissues and to prepare the site for tissue repair. Thus, it helps to restore tissue homeostasis.

Broken mast cells release histamine, bradykinin, etc., which cause dilation of capillaries and small blood vessels. As a result more blood flows in these areas making them red and warm. Therefore, the accumulation of this results into tissue swelling (oedema).
After few days, due to phagocytosis, a cavity containing necrotic tissue and dead bacteria is formed. This fluid mixture is called pus.

6. Acute Phase Proteins
The chemical messenger of immune cells called cytokines are important low molecular weight proteins. These heterogenous proteins stimulate or inhibit the differentiation, proliferation or function of immune cells and also certain viral infections.

7. Natural Killer (NK) Cells
These are non-phagocytic granular lymphocytes which are present in spleen, lymph nodes and bone marrow.

Then can produce perforins or cytolysin which lyses the vi ral infected cells.
These cells can kill a range of tumour cells without any antigen specificity.

Mechanism of Active Aquired immunity
Active acquired immunity is more effective and superior than passive immunity. It occurs in two different forms called cell-mediated and humoral immune responses.
(i) Cell-Mediated Immune Response or Cell-Mediated Immunity (CMI) It is the type of acquired immunity mediated by T-lymphocytes. Activated T-lymphocytes undergo proliferation and differentiate into different types of effector cells, such as T-helper (TH) and T-cytotoxic or killer (Tc) lymphocytes and memory T-lymphocytes (TM). TM confers a long term memory against the invading pathogen. Tc /TK cells directly kill or destroy antigens or antigen bearing pathogens. TH cooperates with B-lymphocyte and triggers its transformation into a plasma cell.

(ii) Humoral response or Antibody-Mediated Immunity (AMI) It is mediated by antibodies present in blood and lymph. Immunoglobulins or antibodies are glycoproteins produced in the body by B-cells in response to an antigen, e.g. IgA. IgG, IgM, IgE and IgD.

B-cells multiple in large number and transform into larger cells called plasma cells or plasmocytes. The transformation into plasma cells in assisted By T-Helper cells (TH). These antibodies destroy antigens by specific antigen-antibody interaction.

Question 5.
Mention the factors causing cancer. Add a note on diagnosis and prevention of cancer.
Answer:
Causes of Cancer
The agents which cause cancer, are called carcinogens.
Cancer can be induced by either physical, chemical or biological agents.

Physical agents These are ionising radiations like X-rays, v-rays and the non-ionising rays like UV-rays which can cause DNA damage leading to neoplastic transformation.
Chemical agents These are tobacco smoke, benzene fumes, arsenic, hormones and aflatoxin, etc.
Nutritional agents Deficiency of some nutrients like vitamins, minerals and proteins causes cancer.
Biological agents Many cancers are caused by viruses. The association of Hepatitis-B and primary liver cancer has been established.
Mechanical factors Trauma, irritation and severe friction have been identified to cause malignancy.
Host factors These include age, sex, marital status, race, socio-economic status, customs and habits of the host.
Environmental factors These include radiation, air pollution, diet, drugs and social environment.
Genetic factors All factors have a genetic basis and are caused by genetic transformations of cells.

Cancer Detection and Diagnosis
Cancer can be detected by the following well-known methods

Blood and bone marrow tests are conducted to know number of cell counts, e.g. WBC count in leukemia.
Biopsy of a piece of suspected tissue is done by cutting thin sections, staining and examining them under the microscope.
Radiography by X-rays is done to detect cancer of the internal organs.
Computed tomography using X-rays is done to generate a 3-D image of internal tissue.
Magnetic Resonance Imaging (MRI) involves the use of non-ionising radiation and strong magnetic field to detect pathological and physiological changes in living tissue.
Monoclonal antibodies against cancer-specific antigens are also used for cancer detection. These are homogenous immunological reagents of defined specificity.
Mammography for detection of breast cancer.
Fine Needle Aspiration Cytology (FNAC)
PAP test (cytological staining) used for detection of cervix cancer.

Prevention
According to WHO, the prevention of cancer is ‘the elimination of or protection against, factors known or believed to be involved in carcinogenesis (formation cancerous tumours) and the treatment of precancerous conditions’.
This implies that cancer cannot be cured at the late-stage so it is better to adopt some preventive measures be for its initiation and progression.

The preventive measures are

Educate people to go for early diagnosis and early treatment for better chance of survival.
Motivate people to know about the oncogenic effects of tobacco.
Prohibit the advertisements of cigarettes and drugs that may increase the chances of cancer.
Maintain personal hygiene.
Control environmental pollution by taking major steps.
Reduce amount of radiation.
Organise occupational health programmes.
Take treatment of cancerous.

Symptoms of Initiation and Progress of Cancer

A hump or hard area in the breast.
A change in wart or mole.
A persistent change in digestive and bowel habit.
A persistent cough or hoarseness, excess loss of blood at the monthly period or loss of blood outside the usual dates.
Blood loss from any natural orifice.
A swelling or sore that does not get better.
Unexplained loss of weight.

Question 6.
Give the structure of HIV. Give an account of infection, control and prevention of AIDS.
Answer:
Structure of HIV:
The virus belongs to retrovirus family and is roughly spherical-shaped with a diameter of 90-120 nm. The core has two single-stranded RNA enveloped with conical capsid mode up of viral proteins P24.
Each RNA fdament is segmented into two identical filaments and associated with nucleo-capsid proteins and enzymes like reverse transcriptase enzyme and integrase.
CHSE Odisha Class 12 Biology Solutions Chapter 9 Health and Diseases 1
Reverse transcription in HIV

Between the capsid and matrix of the virus proteases and other proteins are present. The matrix consists of lipid bilayer of host cell membrane and projecting knob like glycoprotein spikes. It contains two proteins called gpl20 and gp 41. These proteins are required for anchoring to the host cell and entering into it.
CHSE Odisha Class 12 Biology Solutions Chapter 9 Health and Diseases 2
Structure of human immunodeficiency virus

Infection:
HIV infects CD 4 T-lymphocytes and dendritic cells. It anchors to the surface of host cell by adsorption assisted by the glycoprotein. This release the capsid and then the begins the replication of retrovirus begins in the host cell. The HTV lefts untreated then it progresses in three stages

Acute infection Patient develops some symptoms like flu, fever, swollen glands, soar throat, rash, muscle and joint pain and headache, within 2-4 weeks and HIV infection. This stage is at higher risk of transmitting virus through coitus and injectable drugs using contaminated needle.
Clinical latency stage In this case, virus replicates in host cell without expressing symptoms. If patient undergoes retroviral therapy he may live for decades. If he is not on the therapy, then the latency stage lasts on an average for ten years.
Typical (AIDS) stage At this stage, HIV infection acquires its full strength and damages the immune system badly. The value of CD 4 lymphocytes fall below 200 per cubic mililitre of blood. The infected person contracted many other bacterial and fungal diseases.

Some of the prevalent symptoms at this stage are

Weight loss and unexplained tireness
Chronic diarrhoea
Pneumonia
Prolonged swelling of the lymph glands of armpit, groin and neck.
Recurring fever with night sweats.
Persistent cough
Mouth and skin problems
Recurrent infections
Sores of the mouth, anus and genitals .
Without treatment, people who progress to AIDS survive about three years.

Diagnosis:
There are several methods for the diagnosis of HIV infection such as viral culture, Enzyme Linked Iramuno Sorbent Assay (ELISA), PCR test, Western blotting, etc. Out of these, ELISA and Western blotting are widely used.

Prevention:
There is no effective treatment developed to treat AIDS. Therefore, some preventive measures are recommended to prevent its infection

The preventive measures are as follows

Sterlise all surgical instruments before use.
The transfusion of blood should be subjected to HIV test.
Infected mother should avoid pregnancy otherwise, it may also transmit to child.
Heterosexual activites should be prohibited.
Motivate to use condoms during sexual activities.
Proper medical dispose off should be established.

Government of Indian launched national AIDS control board, national AIDS committee, national AIDS control organisation, etc., to create awareness among people about HIV transmission and progression of AIDS.

CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution

July 15, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 8 Question Answer Evolution

Evolution Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Choose the correct options

Question 1.
Life originated on earth about
(a) 2.5 billion years ago
(b) 3.5 billion years ago
(c) 4.5 billion years ago
(d) 5.5 billion years ago
Answer:
(c) 4.5 billion years ago

Question 2.
Which theory proposes the formation of living beings from non-living things?
(a) Theory of panspermia
(b) Theory of abiogenesis
(c) Theory of biogenesis
(d) Theory of special creation
Answer:
(b) Theory of abiogenesis

Question 3.
Who proposed the chemical evolution of life?
(a) AI Oparin – JBS Haldane
(b) Louis Pasteur – AI Oparin
(c) Francesco Redi – JBS Haldane
(d) Spallanzani – Louis Pasteur
Answer:
(a) AI Oparin – JBS Haldane

Question 4.
Which of the following compounds Miller-Urey used in the experimental synthesis of amino acids?
(a) CH₄ NH₃,CO₂ and H₂O
(b) CH₄,NH₃,H₂ and H₂O
(c) CH₄,CO₂ H₂ and H₂O
(d) CH₂,N₂,H₂ and H₂O
Answer:
(b) CH₄,NH₃,H₂ and H₂O

Question 5.
Hot ocean water containing concentrated of prebiotic organic compounds was known as
(a) colloid
(b) crystalloid
(c) gelatinous mixture
(d) primordial soup
Answer:
(d) primordial soup

Question 6.
Which of the following was formed first?
(a) Virus
(b) Prokaryote
(c) Coacervates
(d) Eukaryote .
Answer:
(c) Coacervates

Question 7.
A paper on ‘natural selection’ and ‘origin of species’ was presented in the Linnaean Society of London in 1858 by
(a) Charles Darwin – Robert Malthus
(b) Charles Darwin – Alfred R Wallace
(c) Hugo de Vries – Robert Malthus
(d) Alfred R Wallace – August Weismann
Answer:
(b) Charles Darwin-Alfred R Wallace

Question 8.
Analogous organs have
(a) different origin and similar function
(b) similar origin and similar function
(c) similar origin and different function
(d) different origin and different- function
Answer:
(a) different origin and similar function

Question 9.
Find out the odd match.
(a) Aerial-Flying
(b) Fussorial-Burrowing
(c) Cursorial-Running
(d) Arboreal-Swimming
Answer:
(d) Arboreal-swimming

Question 10.
Which one of the following sets of organs constitutes vestigial organs?
(a) Appendix, coccyx and plica semilunaris
(b) Appendix, pectoral girdle and caecum
(c) Large intestine, coccyx and ear muscle
(d) Appendix, coccyx and rectum
Answer:
(a) Appendix, coccyx and plica semilunaris

Question 11.
What is the correct ascending order?
(a) Mesozoic, Cenozoic and Palaeozoic
(b) Cenozoic, Mesozoic and Palaeozoic
(c) Palaeozoic, Mesozoic and Cenozoic
(d) Palaeozoic, Cenozoic and Mesozoic
Answer:
(d) Palaeozoic, Cenozoic and Mesozoic

Question 12.
Who is known as the ’Father of Modern Palaeontology’?
(a) Leonardo da Vinci
(b) Karl Ernst von Baer
(c) Ernst Haeckel
(d) Georges Cuvier
Answer:
(d) Georges Cuvier

Question 13.
Find the incorrect match.
(a) Blood group ‘A’-Antigen A
(b) Blood group ‘AB’-No antibody
(c) Blood group ‘O’-Andgen A and B
(d) Blood group ‘B’-Antibody anti-A
Answer:
(c) Blood group-‘0’-antigen A and B

Question 14.
Which is not a case of chromosomal aberration?
(a) Recombination
(b) Duplication
(c) Inversion
(d) Translocation
Answer:
(a) Recombination

Question 15.
Which type of natural selection removes individuals from both ends of a phenotypic distribution?
(a) Directional
(b) Disruptive
(c) Stabilising
(d) None of these
Answer:
(c) Stabilising

Question 16.
Which is not a great ape?
(a) Gorilla
(b) Chimpanzee
(c) Orangutan
(d) Macaque
Answer:
(d) Macaque

Question 17.
What is the correct sequence in human evolution?
(a) Homo habilis, H. erectus, H. neanderthalensis, H. sapiens
(b) Homo erectus, H. habilis, H. neanderthalensis, H. sapiens
(c) Homo habilis, H. neanderthalensis, H. sapiens, H. erectus
(d) Homo erectus, H. neanderthalensis, H. habilis, H. sapiens
Answer:
(a) Homo habilis, H. erectus, H. neanderthalensis, H. sapiens

Fill in the blanks

Question 1.
Organic evolution refers to a change in diversity and ……….. in populations of organisms.
Answer:
adaptations

Question 2.
The concept of chemical evolution was proposed by JBS Haldane and a Russian scientist, ………… .
Ans
AI Oparin

Question 3.
Charles Robert Darwin hailed from …………….
Ans
Britain

Question 4.
Charles Robert Darwin went on a voyage on board the ship
Answer:
HMS Beagle

Question 5.
Jean Baptiste de Lamarck wrote a book, entitled ……….., which embodied his theory of inheritance of acquired characters.
Answer:
Philosophic Zoologique

Question 6.
Charles Darwin was inspired by the population theory proposed by …………… .
Answer:
Robert Malthus

Question 7.
Darwin’s contemporary ………… was studying population diversity in the erstwhile East Indies.
Answer:
Alfred Russel Wallace

Question 8.
The mutation theory was proposed by ………….. .
Answer:
Hugo de Vries

Question 9.
All the present day life has originated from a single ancestral form, designated as …………. .
Answer:
protobionts

Question 10.
A gene mutation involving only one nucleotide is called as …………….
Answer:
point mutation

Question 11.
Abiogenesis of simple organic molecules was experimentally proved by ………….. and …………..
Answer:
Miller, Urey

Question 12.
The ‘theory of inheritance of acquired characters was proposed by …………. who hailed from …………. .
Answer:
Lamarck, France

Question 13.
August Weismann’s ……….. theory gave a thunder blow to Lamarckism.
Answer:
germplasm

Question 14.
Charles Darwin studied the diversity of a class of birds, commonly known as ………….. in the Galapagos archipelago.
Answer:
Darwin’s finches

Question 15.
The original title of Darwin’s book was ……………. .
Answer:
‘On the origin of species by means of natural selection’.

Question 16.
Natural selection in action was demonstrated by …………. moth.
Answer:
peppered

Question 17.
The earliest form of horse was ………….. that was living in the plains of North America.
Answer:
Eohippus

Question 18.
The fossil of ……….. discovered from the sedimentary rocks of Bavaria, Germany is the missing link between reptiles and birds.
Answer:
Archaeopteryx

Question 19.
Digits II and IV persist in modern horse as reduced structures, known as ……….. bones.
Answer:
splint

Question 20.
Modifications of the basic pentadactyl limb plan in vertebrates to meet their needs is known as ……….
Answer:
homology

Question 21.
The arrangement of different eras, periods and epochs in their ascending order of time constitutes the …………..
Answer:
geological time scale

Question 22.
Peripatus is connecting link between …………. and …………….
Answer:
Annelida, Arthropoda

Question 23.
………… era is known as the era of reptiles.
Answer:
Mesozoic

Question 24.
Sudden reappearance of some ancestral characters in the present organisms is called as ……………
Answer:
atavism

Question 25.
The effect of …………. is larger in small populations and smaller in large populations.
Answer:
genetic drift

Answer each of the following in one word or more words, wherever necessary

Question 1.
The theory that explains that life originated on this planet from non-living chemical constituents.
Answer:
Theory of abiogenesis

Question 2.
The ocean water that contained concentrated amount of prebiotic organic compounds.
Answer:
Primordial soup or prebiotic

Question 3.
The droplets formed by the separation of high molecular weight organic compounds in a colloidal solution.
Answer:
Coacervates

Question 4.
Protenoids, when dissolved in water by boiling and then cooling, organised structures are formed.
Answer:
Microspheres

Question 5.
Buffon, Erasmus Darwin and Lamarck proposed theories on organic evolution, which had one thing in common.
Answer:
Inheritance of acquired characters

Question 6.
Name the naturalist, who proposed that ontogeny recapitulates phylogeny.
Answer:
Ernst Haeckel

Question 7.
Name the theory, which explains about the origin of amphibians from aquatic fish-like ancestors.
Answer:
Recapitulation theory

Question 8.
DNA → RNA → Protein concept.
Answer:
Central dogma

Question 9.
Genetic recombination occurs in cell division. Name the cell division.
Answer:
Meiosis

Question 10.
Hugo de Vries proposed mutation theory on his observations on the morphological features of a plant. Name the plant.
Answer:
Evening primrose (Oenothera lamarckiana)

Question 11.
Breakage, exchange and rejoining of homologous chromosomal segments.
Answer:
Genetic recombination

Question 12.
A single nucleotide substitution in the nucleotide sequence of a gene.
Answer:
Point mutation

Question 13.
The collection of all genes of a population of species.
Answer:
Gene pool

Question 14.
A sudden change in the genetic make up that ends up in a new expression.
Answer:
Mutation

Write whether the following statements are ‘True’or ‘False’

Question 1.
The primitive atmosphere was reducing.
Answer:
True

Question 2.
Heterotrophic organisms with aerobic respiration evolved prior to anaerobic ’ organisms.
Answer:
False

Question 3.
Continuous genetic variation originates through mutation.
Answer:
False

Question 4.
Serum proteins of closely related animals are similar in their amino acid sequences to a greater extent.
Answer:
True

Question 5.
Reptiles flourished in the Palaeozoic era.
Answer:
False

Question 6.
Close similarity in the nucleotide sequence between two organisms depicts close relationship between them. ‘
Answer:
True

Question 7.
Numerical changes, involving one or both chromosomes of a homologous pair, are known as euploidy.
Answer:
True

Question 8.
Genetic drift is the main driving force of evolution in a large randomly breeding population.
Answer:
True

Question 9.
Discontinuous variation is the product of mutation.
Answer:
True

Short Answer Type Questions

Question 1.
Explain the theory of spontaneous generation.
Answer:
Theory of spontaneous generation It states that life originated from non-living matter automatically. This theory is also known as theory of abiogenesis or autobiogenesis. It was also supported by von Helmont (1642), who claimed that the mice were formed in 21 days from a dirty, sweat-soaked shirt put in a wheat barn in the dark. Abiogenesis was continued to be believed till the 17th century.

Question 2.
What do you mean by chemical evolution?
Answer:
This theory was given by AI Oparin (1923) and JBS Haldane (1928). According to them, the first form of life came from pre-existing, non-living organic molecules (like RNA, protein, etc.) and chemical evolution was followed by the formation of life, i.e. formation of diverse organic molecules from inorganic constituents.

The conditions on the earth favouring chemical evolution were high temperature, volcanic storms and reducing atmosphere containing CH₄, NH₃, etc.

Question 3.
Describe Miller-Urey experiment.
Answer:
Stanley Miller and Harold Urey in 1953 performed an experiment to demonstrate that ultraviolet radiations or electrical discharges or a combination of these can produce complex organic compounds from a mixture of CH₄, NH₃, H₂ and water vapour (H20) at 800° C.

Electric discharge was created in a closed glass flask containing CH₄, NH₃, H₂ in the ratio of 2 : 1 : 2 as shown in figure. The conditions were set similar to those of the primitive atmosphere in the laboratory.

They observed the formation of amino acids while in similar experiments performed by other scientists the presence of complex molecules like sugar, pigments, nitrogen bases and fats in the flask were also observed. Further reactions occurred in the aqueous medium of flask resulted in the formation of complex organic molecules at the bottom of flask, such as polysaccharides, fats, proteins, nucleotides and later nucleic acids (DNA and RNA).

Hence, it was concluded that during the beginning of life on earth; complex organic compounds could have formed simpler inorganic precursors.
CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution 1

Question 4.
Explain prebiotic or primordial soup.
Answer:
Formation of molecular aggregates and cell-like structures Aggregates of complex organic molecules were formed in the oceans of the early earth which was termed the ‘Hot dilute soup or prebiotic or primordial soup’ by JBS Haldane (1920). These were considered as precursors of colloidal particles which could grow and divide. These are small complex molecules which are spherical and are covered by external mambranes.

Question 5.
What is prodigality of reproduction ? Give an example.
Answer:
Prodigality of Reproduction (Overproduction):
All organisms possess enormous fertility. They multiply in a geometric proportion with some organisms producing very large number of species. Despite of this high rate of reproduction of a species, its number remains constant under fairly stable environment. The production of more offsprings by some organisms and fewer by others is termed as differential reproduction.

Question 6.
Write three criticisms on Darwinism.
Answer:
Criticism to Darwinism
Darwin’s theory was widely accepted, but Sir Richard Owen and Adam Sedgewick criticised it due to following • reasons
(i) Darwin emphasised on inheritance of useful variations,. However, sometimes inheritance of small variations, which are not useful to individuals are also seen.
(ii) He could not explain the presence of vestigial organs and concept of use and disuse of organs.
(iii) Darwinism failed to explain the arrival of the fittest.
(iv) Darwinism failed to differentiate between the somatic and germinal variations and considered all types of variations as heritable.

Question 7.
Explain how homologous organs reflect organic evolution?
Answer:
Homologous Organs:
It is the relation among the organs of different groups of organisms, that show similarity in the basic structure and embryonic development, but have different functions. Homology in organs indicates common ancestry.
It is based on divergent evolution which leads to the formation of homologous organs.

Question 8.
Describe homology in early embryonic development.
Answer:
Homologous Organs and Homology:
It is the relation among the organs of different groups of organisms, that show similarity in the basic structure and embryonic development, but have different functions. Homology in organs indicates common ancestry.
It is based on divergent evolution which leads to the formation of homologous organs.

In divergent evolution, a same basic organ gets specialisation to perform different functions, in order to adapt to the different environmental conditions prevailing in the habitat, e.g. forelimbs of vertebrates. Examples of homology are as follows

Structural organisation of vertebrate’s heart, brain, kidney, muscles, skull, etc.
Different mouthparts of some insects.
Forelimbs of animals like – whales, bats, cheetah and mammals (e.g. humans).

Question 9.
Explain the theory of recapitulation.
Answer:
Recapitulation in embryos Von Baer stated that during the embryo development, distantly related animals depart more and more than do closely animals. Ernst Haeckel (1905) reinterpreted Baer’s law in the form of recapitulation theory in the light of evolution. The theory of recapitulation or biogenetic law states that ontogeny (development of embryo) recapitulates phylogeny (ancestral sequence).

Question 10.
How do fossils support organic evolution?
Answer:
The study of fossil in different sedimentary layers indicates the geological period in which they existed. It also shows that the life forms varied over time and certain life forms are restricted to certain geological time scale. Hence, new forms of life have evolved at different times in the history of earth. All this is called palaeontological evidence.

Question 11.
Why do you call Archaeopteryx as a connecting link between reptiles and birds ?
Answer:
Archaeopteryx is a connecting link between reptiles and birds. It was of the size of crow and had both reptilian and avian characters. Presence of teeth in jaws, fingers having claws, long tail with free caudal vertebrae are the reptilian characters. While, presence of feathers on the body, and forelimbs modified into wings are the avian characters.

Question 12.
What do you mean by a geological time scale?
Answer:
Geological. Time Scale:
It covers the whole span of the earth’s history to correlate the evolutionary events in a proper sequence of ascending order of time. On the basis of time, the geological history of the earth has been divided into five eras namely, Archacozoic, Proterozojc, Palaeozoic, Mesozoic and Coenozoic.

Each era includes several periods and each period is further divided into epochs.
The most primitive era, i.e. Archaeozoic is placed at the bottom and the most recent era, i.e. Cenozoic is placed at the top.

Question 13.
Explain serological test.
Answer:
Serological tests These are tests done to study serum and other bodily fluids in animals. In serological tests, close similarity is found in species of a single genus, while genera of the same family show moderate reaction and families of the same order show slight, but detectable similarity. This indicates that closely related organisms show more similarity in protein structure and function.

Question 14.
What is industrial melanism?
Answer:
Industrial Melanism:
Industrial melanism in peppered moth (Biston betularia) in Manchester city is an example of natural selection. In England, 1850s before industrialisation there were more white-winged moths on trees than dark-winged or melanic forms. But after industrialisation, i.e. in 1920, dark-winged moths became more in number than white-winged moths. This is because during industrialisation, the tree trunks became dark due to air pollution (dust and soot particles).

Question 15.
Explain genetic drift.
Answer:
Random Genetic Drift:
Random genetic drift refers to a random change in gene frequency of a population. In small population, frequencies of particular alleles may change drastically by a single change alone. These changes usually occur randomly.

Sewall Wright recognised this phenomenon as genetic drift (also known as Sewall Wright effect.) In large population, this phenomenon is rare because only favourable variations are selected by nature and unfit variations are eliminated.
Thus, genetic drift acts as the driving force for evolution in large populations.

Question 16.
What is speciation ?
Answer:
Speciation:
It is the process of formation of one or more new species from an existing species due to the accumulation of inversible adaptive change in their structure. A species is a collection of a group of populations with common gene pool (i.e total collection of all genes and its allele in a population). The factors which influence speciation, include mutation, recombination, natural selection, hybridisation, genetic drift, polyploidy (i.e increase in number of chromosomal set) and isolation.

Question 17.
What is bottleneck effect ?
Answer:
Bottleneck Effect:
It occurs when there is a disaster of some sort that reduces the size of a large population to an insignificance. This leaves smaller variation among the small number of surviving individuals, which disables natural selection to operate. In this situation, random genetic drift becomes main driving force of evolution.

Question 18.
What is Hardy-Weinberg’s principle?
Answer:
Mutations introduce new genes into a species resulting in the change in gene frequencies. In 1908, GH Hardy and W Weinberg established a simple mathematical relationship to the study these gene frequencies and gave Hardy-Weinberg principle.

This principle states that the allele frequencies in a . population are stable and is constant from generation to generation, i.e. gene pool remains constant. This is .called genetic equilibrium or Hardy-Weinberg equilibrium.

Differentiate between the following

Question 1.
Abiogenesis and Biogenesis.
Answer:
Differences between abiogenesis and biogenesis are as follows

Abiogenesis	Biogenesis
A theory which describes the origin of life on the earth from non-living thing is called Abiogenesis.	A theory which describes the origin of life on the earth from pre-existing living organisms is called Biogenesis.
It is based on observations and thoughts.	It was based on practical experiments and ffiaterial evidence.
It was supported by the fungus of bread and production of frogs in the mud.	It was supported by the experiments performed by Redi and Pasteur.
It gives no scientific reasoning about the production of life.	It describes the process of reproduction as an essential ability of living organism.

Question 2.
Chemoautotrophs and Photoautotrophs
Answer:
Differences between chemoautotrophs and photoautotrophs are as follows

Chemoautotrophs	Photoautotrophs
These are the organisms which obtain their energy by oxidising electron donor.	Phototrophs are the organisms that capture protons in order to acquire energy.
Energy source is the oxidizing energy of chemical compounds.	Energy source is mainly sunlight.
Classified as chemoorganotrophs and chemolithotrophs.	Classified as photoautotrophs and photoheterotrophs.
Examples include nitrifying bacteria like Nitrosomonas, sulfur bacteria like Thiothrix, etc.	Some examples are plants algae, cyanobacteria and phytoplanktons.

Question 3. Chemical evolution and Biological evolution.
Answer:
Differences between chemical evolution and biological evolution are as follows

Chemical evolution	Chemical evolution
It occurs due to changes in the structure of molecules from complex molecules to simple molecules with the passage of time.	It occurs due to changes in the structure of molecules from complex molecules to simple molecules with the passage of time.
It is relatively fast process and hence, it is possible to prove it in a laboratory.	It is relatively fast process and hence, it is possible to prove it in a laboratory.
It involves the evolution of chemical such as water vapour, methane, ammonia and hydrogen into organic molecules such as sugars which later combined to form big molecules such as proteins, RNA and DNA.	It involves the evolution of chemical such as water vapour, methane, ammonia and hydrogen into organic molecules such as sugars which later combined to form big molecules such as proteins, RNA and DNA.
Chemical evolution came into act before organic evolution.	Organic evolution is a consequence of biological evolution.

Question 4.
Homologous organs and Analogous organs.
Answer:
Differences between homologous organs and analogous organs

Homologous organs	Analogous organs
They have same basic structural plan.	They have totally different structural plan.
They are found in closely related organisms which arise from some common ancestor.	These organs found in totally unrelated organisms.
They differ in appearance.	They have similar appearance.
They are modified to carry out different functions.	These organs carry out the same function.
They lead to adaptive radiation or divergent evolution.	They lead to convergent evolution or adaptive convergence.

Question 5.
Moulds and Casts.
Answer:
Differences between moulds and casts are as follows

Moulds	Casts
A mold is a cavity left behind when the organic material is dissolved away. Only the external impressions remain during fossilisation.	A cast is usually a very finely preserved representation of the surface features of the organism during fossilisation.

Question 6.
Genetic recombination and Mutation.
Answer:
Differences between genetic recombination and mutation are as follows

Genetic recombination	Mutation
It is the production of offspring with combinations of traits that differ from those found in either parents.	It is random nucleotide alterations such as copying errors or changes induced by external mutagens.
It is performed by the cell during the preparation of gametes (sperm, egg, pollen) which are used for sexual reproduction.	It may take place both in somatic cells and germline cells.
Genetic recombination is heritable.	Mutation can be heritable as well as non-heritable.

Question 7.
Somatic variation and Germinal variation.
Answer:
Differences between somatic variations and germinal variations are as follows

Somatic variations	Germinal variations
Somatic variations are the variations in the somatic cells of an organism which may be acquired by them in their life.	Germinal variations are the variations in the germ cells of an organism.
These are not passed on to their progenies.	These are passed on to their progenies.

Question 8.
Chromosomal aberration and Gene mutation.
Answer:
Differences between chromosomal aberration and gene mutation are as follows

Chromosomal aberration	Gene mutation
Chromosomal aberration is any change in the number and structure of chromosomes in an organism.	Gene mutation is an alteration that occurs in the DNA base sequence of a gene.
It can change the total number of chromosomes in an organism.	Gene mutation does not cause changes in the total number of chromosomes in an organism.
It may include many gene alterations.	Gene mutation commonly refers to a single gene alteration.
Damages due to chromosomal aberration are large scale compared to gene mutation.	Nucleotide damage is small in scale compared to chromosomal aberration. However, it can cause serious health problems.

Question 9.
Euploidy and Aneuploidy.
Answer:
Differences between euploidy and aneuploidy are as follows

Euploidy	Aneuploidy
Euploidy is a variation in a chromosomal set of a cell or organism.	Aneuploidy is a variation in total chromosome number of a cell or organism.
The number of chromosome sets is changed.	The number of chromosome sets is not changed.
Cells have states of 3n, An, etc.	Ceils are in the states of 2n+1, 2n-1, n-1,n+1, etc.
Euploidy occurs due to fertilisation of one ovum with two sperms, etc.	Aneuploidy arises due to non-disjunction in meosis I and II and mitosis.
Euploidy is not seen in humans.	Aneuploidy is seen in humans.

Question 10.
Natural selection and Genetic drift.
Answer:
Differences between natural selection and genetic drift are as follows

Natural selection	Genetic drift
It is a process where more adaptive species are selected in response to the environmental challenges.	It is a random selection.
It occurs due to environmental challenges.	It does not occur due to environmental challenges.
It ends up with selecting the more successive trait over the detrimental trait.	Due to genetic drift important alleles may disappear completely.
It increases the frequency of the trait more adaptive to the environment.	Genetic drift rarely results in more adaptive species to the environment.
It increases genetic variation.	It does not increase genetic variation. Infact, sometimes it causes some variants to be extinct completely.

Question 11.
Convergent evolution and Divergent evolution
Answer:
Differences between convergent evolution and divergent evolution are as follows

Convergent evolution	Divergent evolution
It is supported by the analogous structures.	It is supported by the homologous structures.
It occurs in organisms which are not closely phylogenetically related.	It occurs in phylogenetically related organisms.
Example insects, birds, pterosaus and bats. All have developed the similar nature of the flight/wings.	Example Darwin’s finches.

Long Answer Type Questions

Question 1.
Give an account of the chemical basis of origin of life.
Answer:
Life on earth appeared 500 million years after its formation. In order to explain origin of life on the earth, different theories were given by different thinkers and scientists. They are
1. Theory of special creation It states that God has created life by his divine act of creation, i.e. the earth, light, plants and animals are all being created by the supernatural power.

2. Theory of catastrophism It states the creation of new life forms occurred after each catastrophe on earth.

3. Cosmozoic theory or Theory of panspermia It was given by early Greek thinkers, which states that the life on earth arose from the spores or panspermia, which came from outer space and developed into living forms.
The above three theories have been discarded due to the lack of logical explanation. Later on few more theories were proposed to explain the orgin of life.
These are
(i) Theory of spontaneous generation It states that life originated from non-living matter automatically. This theory is also known as theory of abiogenesis or autobiogenesis. It was also supported by von Helmont (1642), who claimed that the mice were formed in 21 days from a dirty, sweat-soaked shirt put in a wheat barn in the dark. Abiogenesis was continued to be believed till the 17th century.

(ii) Theory of biogenesis According to this theory, life originates from pre-existing life. This theory was supported by some scientists like Francisco Reddi (1668), Lazzaro Spallanzani (1767), Louis Pasteur (1862), Harvey and Huxley.

Chemical Evolution:
This theory was given by AI Oparin (1923) and JBS Haldane (1928). According to them, the first form of life came from pre-existing, non-living organic molecules (like RNA, protein, etc.) and chemical evolution was followed by the formation of life, i.e. formation of diverse organic molecules from inorganic constituents.
The conditions on the earth favouring chemical evolution were high temperature, volcanic storms and reducing atmosphere containing CH₄, NH₃, etc.
Chemical Evolution has Occurred in Following Steps

(i) Primitive earth had no atmosphere and it was anaerobic. Initially, the earth was a ball of hot gaseous mass.

(ii) Formation of Early Molecules
(a) Earth gradually began to cool and condense into a solid form. As a result, the free atoms or elements present on earth began to segregate into three concentric masses according to their weight.

(b) The heavier elements like nickel, iron, etc., moved to the core of the earth, intermediate one like silicon and aluminium moved to the middle and the lighter elements like oxygen, nitrogen, hydrogen, carbon, etc., remained on the surface and formed the early atmosphere of earth.

(c) With further cooling of the earth lighter elements such as water (H₂O), methane (CH₄), ammonia (NH₃), hydrogen cyanide (HCN) . and oxides of carbon were formed. The primary atmosphare was devoid of free molecular oxygen (O₂) due to which it was of reducing type.
Hot oceans, seas, lakes and other water bodies were formed due to the accumulation of heavy rainwater in the depressions of the earth.

(iii) Formation of simple organic molecules The high concentration of simple inorganic compounds (CH₄,HCN,NH₃) in water bodies induces them to react with each other so as to produce some unsaturated hydrocarbons.

As a result of further interaction of these hydrocarbons, some simple organic compounds such as simple sugars (e.g. glucose, ribose, deoxyribose, etc.), nitrogenous bases (purines like adenine, guanine and pyrimidines like thymine, cytosine and uracil), amino acids, fatty acids and glycerols were formed.

The energy required for these reactions came from the following sources

Solar radiations like ultraviolet light (UV) rays, cosmic rays and X-rays, etc.
Electrical discharge from lightning. High energy radiations from radioactive unstable isotopes on primitive earth.

(iv) Formation of complex organic molecules A number of hydrocarbons, purines and pyrimidine bases, amino acids, fatty acids, sugars and other organic compounds were accumulated in the primitive seas. Further reactions like polymerisation lead to the formation of larger organic molecules which later on formed complex organic molecules like polysaccharides, fats, proteins, nucleotides and then nucleic acids (DNA and RNA).

(v) Formation of molecular aggregates and cell-like structures Aggregates of complex organic molecules were formed in the oceans of the early earth which was termed the ‘Hot dilute soup or prebiotic or primordial soup’ by JBS Haldane (1920). These were considered as precursors of colloidal particles which could grow and divide. These are small complex molecules which are spherical and are covered by external mambranes.
These colloidal aggregrates were called coacervates by Oparin and microspheres by Sydney Fox (1965).

The firest non-cellular cells were believed to contain nucleoproteins and other macromolecules like polypeptides, lipids, etc. These cells were called protocells or protobionts or eubionts and they in the ancient ocean represented the beginning of life approx. 3.5 billion years ago. Probably viruses were evolved at the same time.

The first cellular life forms are believed to be evolved approximately 2 billion years back by the aggregation of various non-living molecules. From there, the evolution of diverse species of organisms occurred in course of time.

Question 2.
Discuss the evidences of organic evolution from comparative anatomy and morphology.
Answer:
Evidences from Comparative Anatomy and Morphology
These evidences help to identify the similarities and differences among the organisms of today and those that existed years ago. Comparative study of external and internal structure can be used to understand the occurrence of organic evolution.

These can be determined by the following types
Homologous Organs and Homology
It is the relation among the organs of different groups of organisms, that show similarity in the basic structure and
embryonic development, but have different functions. Homology in organs indicates common ancestry.
It is based on divergent evolution which leads to the formation of homologous organs.

In divergent evolution, a same basic organ gets specialisation to perform different functions, in order to ‘ adapt to the different environmental conditions prevailing in the habitat, e.g. forelimbs of vertebrates. Examples of homology are as follows

Structural organisation of vertebrate’s heart, brain, kidney, muscles, skull, etc.
Different mouthparts of some insects.
Forelimbs of animals like – whales, bats, cheetah and mammals (e.g. humans).

Flomologous organs as exhibited by the forelimbs of vertebrates; (a) Fluman, (b) Bat, (c) Whale, (d) Horse

Adaptive Radiation (Divergent Evolution):
It is the diversification of the organisms of a population into a number of new groups with adaptive characters suiting their need for survival.

Thus, it can be concluded that adaptive radiation and divergent evolution are interrelated and based on the modification of homologous structures. This can be proved studying the basic pattern of the pentadactyl limb which has undergone adaptive modifications in vertebrates,

All these animals have five digits (pentadactyl) in their forelimbs. All these digits possess the same number of skeletal elements that are arranged in same order (i.e. proximal to distal) along with similar muscle, nerve fibres, blood vessels, etc. These limbs have undergone adaptive modifications so as to perform the required funtions to adapt to their environment.

Similar adaptive modification rule also applies to mammals. In figure, a typical pentadactyl limb is seen in a terrestrial mammal.
CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution 3
Adaptive radiation in the limb structure of mammals

This pattern has been modified for different functions like running (cursorial), swimming (aquatic), flying (aerial), climbing (arboreal) and burrowing (fussorial). Thus, all mammals have originated from an ancestral terestrial mammal through adaptive modifications of the basic pentadactyl limb plan.

Analogous Organs and Analogy:
In contrast to homologous organs, the analogous organs are different in their basic structure and developmental origin, but appear same and perform similar functions.
This relationship between the structures of different groups of animals due to their similar functions is called analogy or convergent evolution.

Examples of analogy are as follows
1. Wings of an insect a bird, Pterosaur (extinct flying reptile and a bat (flying mammal) show analogy. The wings are modified forelimbs that are adapted for flight.
The internal organisation of vertebrate (reptile, bird and bat) wings is same and they are composed of muscles and bones whereas, the wings of insect do not possess bones and muscles. They are only thin membranous extentions of exoskeleton and are made up of chitin.
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2. Flippers of dolphin and penguin.
3. Fins of fishes and flippers of whales.
4. Tracheae of an insect and lungs of the vertebrates are adapted for respiration, but are not homologous, as tracheae are ectodermal in origin, whereas the lungs are endodermal in origin.

Adaptive Convergence (Convergent Evolution):
In adaptive convergence, separate lineages show similar morphology under the influence of similar environmental factors. The existence of analogous structures also suggest the occurrence of convergent evolution. It may be explained in terms of the environment acting through the agency of natural selection and favouring those variations which confer increased survival and reproductive potential of the organisms possessing them.
Marsupial mammals in Australia are a good example to study adaptive convergence or convergent evolution.

Vestigial Organs:
The degenerated, rudimentary organs which are non-functional in the possessor, but were functional in their ancestor and in related animals are called vestigial organs. There are more than 90 vestigial organs in the human body. Some examples in human are coccyx (tailbone), nictitating membrane ( semilunar fold or plica semilunaries or 3rd eyelid), caecum, vermiform appendix, canines, wisdom teeth, tonsils, body hair, auricular muscles, mammary glands in males, etc.
CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution 5
Vestigial organs are present in some other animals also, e.g. splint bones representing metacarpals of digits II and IV in horse, small bones representing hindlimbs and pelvic girdle in python and boas, wings and feathers in flightless bird kiwi of New Zealand, etc.

In plants, Dandelions and some other asexually reproducing plants retains flower which produce pollen grains necessary for sexual reproduction.

Atavism or Reversion:
It is the sudden reappearance or refunctioning of some ancestral organs, which have either completely disappeared or are present as vestigial organs.

It supports the idea of organic evolution, that living organisms have the ability to develop even lost or non-functional structures. For example, long and dense body hair, ability to move pinna in .some individuals, birth of a human baby with a small tail, presence of additional mammae in some individuals, elongated canine teeth, etc.

Question 3.
Give an account of the embryological evidences of organic evolution.
Answer:
Evidences from Embryology:
Similarities and degree of intimacy in the embryonic development of various animals provide the supportive evidences of organic evolution. Some conclusions are derived from the study of comparative embryology, which are as follows

1. Common developmental pattern A common pattern of development is found in all the multicellular organisms. The development of embryo by sexual reproduction starts from diploid zygote or fertilised egg. The zygote undergoes repeated cleavage or cell division to form a solid structure called morula. The morula divides to form blastula, i.e. a single-layered hollow structure, which finally develops into gastrula, i.e. two to three-layered structure.

The animals with two-layered gastrula are termed as diploblastic, e.g. in coelenterates. The animals in which three-layered gastrula is found are known as triploblastic, e.g. frog, lizard, etc. These two or three layers of gastrula are termed as primary germ layers, which give rise to the entire animal. Thus, the similar early embryonic development shows close relationship among all the multicellular organisms.

2. Similarity in early embryos of vertebrates If a comparative study of embryos of vertebrates at same age is done, it is observed that they resemble one another. Such similarities suggest that these animals have common ancestry.

Some similarities in early embryonic stages are as follows
Presence of gill clefts, notochord, tail, rudimentary eyes and ears, etc. in all vertebrates from fishes to mammals.
Notochord is replaced by vertebral column in all adult vertebrates.
Gills are replaced by lungs in adult amphibians, reptiles and mammals.
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3.Recapitulation in embryos Von Baer stated that during the embryo development, distantly related animals depart more and more than do closely animals. Ernst Haeckel (1905) reinterpreted Baer’s law in the form of recapitulation theory in the light of evolution. The theory of recapitulation or biogenetic law states that ontogeny (development of embryo) recapitulates phylogeny (ancestral sequence).

This means that the life history of an animal reflects its evolutionary history. For example, during the life history, frog’s tadpole larva resembles fishes in habits and structure. It suggests that amphibians have evolved from fish ancestors.
Embryo logical Evidences in Plants

These include

Presence of filamentous green algae-like structure, i. e. protonema during development of Funaria (moss).
Pteridophytes and primitive -gymnosperms like Cycas and Ginkgo have flagellated sperms and they depend on water for fertilisation. It strengthens the fact that gymnosperms have evolved from pteridophytes.

Question 4.
Describe palaeontological evidences of organic evolution.
Answer:
Evidences from Palaeontology:
Palaeontology is the study of fossils of plants and animals that lived in prehistoric times. Leonardo da Vinci (1452-1519), an Italian painter is known as the ‘Father of Palaeontology’ and Baron Georges Cuvier (1769-1832) is known as ‘The Founder of Modern Palaeontology’.

The study of fossil in different sedimentary layers indicates the geological period in which they existed. It also shows that the life forms varied over time and certain life forms are restricted to certain geological time scale. Hence, new forms of life have evolved at different times in the history of earth. All this is called palaeontological evidence.

Fossils:
These are the material remains (bones, teeth, shells) or traces (physical or chemical) of ancient organisms induding plants and animals. According to Charles Lyell, fossil is any body or traces of body of animal or plant buried and preserved by the natural causes. .

Fossilisation is the process of formation of fossils. Fossils are generally preserved in sedimentary rocks in which multiple layers are present and the lowermost layer gets harden into rock under pressure. These are formed when parts of dead organisms decay with the passage of time and get replaced by inorganic materials. The hard parts of the body (i.e. bone, teeth, shell, etc.), are preserved more readily than soft parts, into rocks. Both animals as well as plants can be fossilised as additional layers get deposited with time.

Fossils are also formed by processes other than petrification, e.g. an organism may get buried intact in ‘ preservatives like resins, snow, oil, tar, volcanic, ash, etc.

Sometimes, the organism or its parts get washed away to water bodies and settle down at the bottom. Gradually they get covered by the layers of mud and sand. Particularly when buried in rapidly hardening mud, they decay completely and the space it occupies, becomes filled with another kind of material forming moulds and casts.

Types of Fossils:
Some general types of fossils are given below
(i) Unaltered It includes animals, plants and humans who got embedded in permafrost of arctic/alpine snow and remain preserved in actual state, e.g. wooly mammoth (25000 years old in Siberia) and insects trapped in the amber of plants.
(ii) Petrifications The fossils in which hard body parts (organic matter) get replaced by mineral matter like silica, pyrites and calcium, etc. In some petrified fossils, even cellular details are found. This process is used to preserve original structures of organisms.
(iii) Moulds They are hardened encasements formed in the outer parts of extinct organic remains which later decayed leaving cavities.
(iv) Casts They are hardened pieces of mineral matter deposited in the cavities of moulds.
(v) Impressions/Imprints They are external features of organisms or their parts that are left due to hardening rocky matter before they completely decay.
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(a) Imprint of a crustacean, (b) Mould of a bivale, (c) Insect trapped in amber, (d) Petrified softwood, (e) Petrified cone of Araucaria mirabilis (a coniferous tree)

Important Characteristics of Fossils:
The fossil records are direct evidences that support organic evolution due to the following reasons
1. Fossils of different ages are mostly found in the different layers of sedimentary rocks in an ascending order, i.e. from simple to complex forms.

2. The lower layers of rocks of early era contain fossils of simple nature. In upper layers more recent fossils, which are more recent and complex in structure. Fossils are not found in the rocks of the Archaeozoic (first) Era.

3. In the rocks of the second era, i.e. Proterozoic, only few fossils are found. These are simple, soft-bodied organisms, such as marine invertebrates. In the upper strata of rocks, fossils are more in number, belonging to organisms of later ages.

4. The fossils of two consecutive strata are different from each other indicating the occurrence of progressive changes in course of time.

5. Certain mammals, such as horse, elephant, camel and man, have complete fossil records. They clearly explain the gradual evolution of these species.
CHSE Odisha Class 12 Biology Solutions Chapter 8 Evolution 8

6. Fossils of some transitional forms (also called connecting links or missing links) explain the emergence of a new species from its ancestor. For example, fossil of Archaeopteryx discovered from the rocks of Jurassic Period at Bavaria, Germany in 1861 is a connecting link between birds and reptiles. As a transitional form, it possessed the characters of both reptiles and birds.

7. Living fossils are the living organisms which are similar in appearance to a recorded fossil of distant ancestors but they usually have no close relatives. Such organisms have undergone very slow changes over a long span of time, e.g Latimeria (a coelacanth fish).

8. The approximate ages of fossils can be determined by different radioactive dating methods.

9. Extinction of species can be explained by the fossil records of that species, e.g. dinosaurs extinct about 66 million years ago.

Question 5.
Describe Darwin’s theory of natural selection and origin of species and discuss about the criticisms.
Answer:
Darwinism (Natural Selection Theory):
Charles Robert Darwin was born in 1809. In 1831, he accepted an unpaid post of naturalist on the survey ship, called HMS Beagle. In his voyage, he spent five years in sea charting the East Coast of South America. During a five week stay on the Galapagos Archipelago Islands, he was struck by the similarities shown by the flora and fauna of the islands and mainland. In particular, he was intrigued by the characteristic distribution of species of tortoises and finches.

Darwin observed different types of beaks in the same population of finches. He termed this phenomenon as adaptive radiation which explains that the changes in beak structure were the result of adaptations to the available food to the native finches. Over the years, the ancestral beak evolved into diverse types of beaks. Thus, Darwin realised the importance of competition and adaptation in the evolution of finches.

After his return, Darwin formulated his concept of organic evolution. He was also influenced by a paper published by Robert Malthus (1838) on populations, which states that the population increases in a geometric progression, while the food supply increases more slowly. Therefore, the food supply becomes a limiting factor. In the meantime, another naturalist Alfred Russel Wallace, came to the same conclusions as Darwin regarding natural selection. The content of Wallace’s write-up was similar to Darwin’s thinking.

Darwin and Wallace presented papers on their ideas which were published in the ‘Journal of the Proceedings of The Linnaean Society of London in 1858. Darwin published a book entitled ‘On the Origin of Species by Means of Natural Selection (later changed to ‘Origin of Species’ In its 6th edition in 1872), embodying his observations and conclusions in 1859.

Postulates of Darwinism:
The main postulates, which formed the basis of Darwin’s theory of natural selection are as follows
(i) Prodigality of Reproduction (Overproduction):
All organisms possess enormous fertility. They multiply in a geometric proportion with some organisms producing very large number of species. Despite of this high rate of reproduction of a species, its number remains constant under fairly stable environment. The production of more offsprings by some organisms and fewer by others is termed as differential reproduction.

(ii) Limiting Factors
The resources like food, space, etc., remain limited inspite of rapid multiplication of the individuals of all the species. It helps to check the increased number of animals and plants.

(iii) Struggle for Existence
The limited amount of resources and overproduction of organisms are the main causes of struggle for existence. Various types of struggle help an organism to cope up with unfavourable environmental conditions.
The three types of struggles are as follows
(a) Intraspecific struggle It is the struggle among the individuals of same species for their common requirements like food, shelter, mate, breeding places, etc.
(b) Interspecific struggle It is the struggle between the individuals of different species for their similar requirements like food and space.
(c) Environmental struggle It is the struggle of living forms against the environmental conditions like extreme heat, cold, drought, earthquakes, storms, disease, volcanic eruption, etc.

(iv) Variations and Heredity
All individuals are dissimilar in some of their characters except the identical twins. This dissimilarities are mainly due to the variations. These are the small or large differences among the individuals. Variations allow some individuals to better adjust with their environment.

Variations can be categorised into the following types
1. Somatic variations These variations affect the somatic cells of an organism. They are also called modifications or acquired characters because they are aquired by an individual during its lifetime. These are caused by various environmental factors, use and disuse of organs and conscious efforts, etc.
2. Germinal variations These are inheritable variations recognised by Darwin but he had no idea of inheritance of characters. They are formed mostly in germinal cells. They are further of two types
• Continuous (gradual) variations These are fluctuating variations, which oscillate due to race, variety and species.
• Discontinuous (sudden) variations These appear suddenly and show no ‘spots’ gradation. These variations were termed as ‘spots’ by Darwin and ‘mutation’ by Hugo de Vries. Darwin regarded continuous variations to be more important because the discontinuous variations being mostly harmful would not be selected again.

(v) Survival of the Fittest and Natural Selection:
The organisms, which have inherited favourable variations generally survive. This is termed as ‘survival of the fittest’ (the phrase being originally used by Herbert Spencer). Whereas, the organisms without such variations appear unfit and get eliminated. Nature plays a decisive role in selecting the fit organisms.

Natural selection is based on merit and is without any prejudice or bias. It eliminates the unfit ones and selects those organisms that are most fit to survive in a particular environment and to produce offsprings. Survival alone does not make any sense from evolution point of view.
The fit organisms must reproduce to contribute to the next generation. Lerner (1959) says, ‘Individuals having more offsprings are the fit ones’.

(vi) Origin of New Species (Speciation):
Darwin considered that as a result of struggle for existence, variability (continuous variations) and inheritance, species became better adapted to their environment. These beneficial adaptations are preserved and accumulated in the individuals of species generation after generation. This results into the origin of new species or speciation and the resultant offsprings become visibly distinct from their ancestors.

Criticism to Darwinism:
Darwin’s theory was widely accepted, but Sir Richard Owen and Adam Sedgewick criticised it due to following reasons
(i) Darwin emphasised on inheritance of useful variations,. However, sometimes inheritance of small variations, which are not useful to individuals are also seen.
(ii) He could not explain the presence of vestigial organs and concept of use and disuse of organs.
(iii) Darwinism failed to explain the arrival of the fittest.
(iv) Darwinism failed to differentiate between the somatic and germinal variations and considered all types of variations as heritable.
(v) Darwin’s natural selection theory was based on the mistaken concept of artificial selection. He wrongly believed that changes brought on by domestication of animal were also heritable.
(vi) Darwin failed to recognise the large fluctuating variations (occurring due to mutation). He only believed in the occurrence of small continuous variations.

Darwin proposed ‘theory of pangenesis’ explaining that pangenes or gemmules are transmitted from one generation to next. However, this theory was refuted by Weismann’s germplasm theory.

Question 6.
Discuss about the synthetic theory of organic evolution.
Answer:
Modern Synthetic Theory of Organic Evolution:
The fundamental mechanisim of evolution as explained by Darwin and his contemporaries underwent major modification with the progress in genetics.

Mendel’s laws of inheritance were applied to various theories (like natural selection). The validity of these laws were later verified by Correns, Tschermark and de Vries. It came to light that mutation and genetic recombination were the cause of genetic variation in living organisms.

These variations were used as the raw material on which natural selection acted on, leading to evolution of new species. The process of evolution as a population character not an individual one was later on proposed by GH Hardy and W Weinberg. According to them, a disturbance in the gene pool of a population results in evolution. Among these new developments, the concept of modern synthetic theory (post-Darwinian synthesis) was proposed.

The modern synthetic theory is based on the work of a number of scientist namely-Dobzhansky’s (1937) Julian Huxley (1942), Ernst Mayr (1970), RA Fisher (1958), JBS Haldane, Sewall Wright (1968) and GL Stebbins (1971). Stebbins in his book ‘Process of Organic Evolution discussed the modern synthetic theory.

This theory is a collective explanation of the fundamental mechanism of evolution. Homologous recombination, mutation, natural selection, isolation, genetic drift and migration form the basis of the mechanism of evolution.

Genetic Recombination:
These are the homologous combinations between genes present on different chromosomes (i.e. paternal and maternal) during gametogenesis. It can occur by following ways
(i) Crossing over Mutual exchange of genes between non-sister chromatids of homologus chromosomes during meiosis-I. It forms multiple variations in a population.
(ii) Independent assortment of chromosomes It forms genetically different haploid gametes during meiosis which bring about variations in new generation.
(iii) Random fusion of gametes During sexual reproduction, random fusion of male and female gametes produces a new individual.

Changes in Chromosome Number and Structure:
Chromosomal mutations or aberrrations arise due to change in number and structure of chromosomes. Chromosomal number may change in followinng two ways
(i) Polyploidy (increase in number of chromosome sets)
(ii) Aneuploidy (change in number of one or both chromosomes of a homologous pair). When the change occurs in the chromosomal morphology, it is called chromosomal aberration.

These are of four types
(i) Deletion Loss of a segment of a chromosome.
(ii) Duplication Doubling of a chromosomal segment.
(iii) Inversion Reversal in the order of genes.
(iv) Translocation Mutual exchange of a segment of chromosome between two non-homologous chromosomes.

Gene Mutations:
In 1901, Hugo de Vries carried out experiments on evening primrose plant (Oenothera lamarckiana) and proposed the mutation theory of evolution. This theory states that the evolution occurs by the sudden large differences or mutations in the population. Mutation is the sudden change in appearance or variations in an individual or a population. When mutation affects only a single nucleotide, it is called point mutation.

However, when more than one nucleotide is involved in mutation, it is called gross mutation. These mutations results in drastic changes which can be lethal or insignificant or useful. They lead to the new phenotypes. Though mutations are random and occur at very slow rates, they are sufficient to create considerable genetic variations for speciation to occur.

Natural Selection:
It is the most widely accepted theory for explaining the mechanism of evolution, profounded by Charles Darwin and Alfred Russel Wallace. Natural selection selects the favourable variation and allows such organisms to reproduce. Meanwhile, harmful or non-adaptive variations are discouraged by natural selection and such organisms are eliminated from the population. Therefore, variations act as raw material natural selection which decides the favourable traits to continue through generations.

Isolation:
The mechanism by which a population gets segregated into two or more subtypes by a geographical barrier, such that each subtype influences a different environment, is called isolation.
This segregation can occur due to
(i) Geographical isolation When two related populations occupy geographically or spatially separated areas.
Such species are called as allopatric species. These species become so different to each other that when they are brought together, they fail to reproduce.
(ii) Reproductive isolation The prevention of interbreeding between the population of two different species. Such reproductively isolated species are called as sympatric species.

CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance

July 14, 2025 by Prasanna

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 7 Question Answer Molecular Basis of Inheritance

Molecular Basis of Inheritance Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Fill in the blanks with correct answers from the choices given in the brackets of each bit

Question 1.
In split genes, the coding sequences are ……….. (introns, operons, exons, cistrons)
Answer:
exons

Question 2.
The smallest part of the gene is called …………… (recon, muton, exon, cistron)
Answer:
cistron

Question 3.
The enzyme referred to as Kornberg enzyme is ……….. (DNA polymerase-I, DNA polymerase-II, RNA polymerase, ligase)
Answer:
DNA polymerase-I

Question 4.
The polymerase that has 5′-3′ exonuclease property is known as ………… (DNA pol-I, DNA pol-II, RNA pol, DNA ligase)
Answer:
DNA pol-I

Question 5.
The termination factor that recognises the termination codon UAG is ………….. (only RF₁, only RF₂, both RF₁ and RF₂, neither RF₁ and RF₂)
Answer:
Only RF

Question 6.
The enzyme that removes formyl group from the first amino acid methionine of a newly synthesised polypeptide is ………… (RF₃ translocase, deformylase, exoaminopeptidase)
Answer:
deformylase

Question 7.
The word gene was coined by ……….. (Garrod, Johannsen, Meischer, Griffith)
Answer:
Wilhelm Johannsen

Question 8.
In 1869 …………… discovered DNA.(Garrod, Meischer, GrifFith, Wilkins)
Answer:
Friedrich Meischer

Question 9.
The virulent, pneumococcus possessed a …………. coat for its protection. (protein, lipid, phospholipid, polysaccharide)
Answer:
polysaccharide

Question 10.
Complete sequence of amino acids in ………….. was proposed by Sanger. (insulin, haemoglobin, kinetin, polymerase)
Answer:
insulin

Question 11.
RNAs lack ………. as nitrogenous base. (adenine, guanine, cytosine, thymine)
Answer:
thymine

Question 12.
One complet turn of B-DNA contains ………….. number of nitrogenous bases. (10,11,9,12)
Answer:
10 .

Question 13.
The most stable form of RNA is …………. RNA. (messenger, transfer, ribosomal, small nuclear)
Answer:
ribosomal

Question 14.
When a codon codes or more than one amino acid, it is called ………….. code.
(commaless, degenerate, nonsense, universal)
Answer:
degenerate

Question 15.
The start codon is ………… (UAA, UGA, AUG, UGA)
Answer:
AUG

Express in one or two word(s)

Question 1.
If in a double-stranded DNA there is 25% of thymine, then calculate the per cent of guanine.
Answer:
25%

Question 2.
What is the complementary base of adenine in RNA?
Answer:
Uracil

Question 3.
In a double helix if one stand is on 5′ → 3′, what will be arrangement of other strand?
Answer:
3′ → 5′

Question 4.
What are the basic proteins called in eukaryotic DNA?
Answer:
Histones

Question 5.
What is called to amino acids with more than one codon?
Answer:
Degenerate

Question 6.
What type of genes do express continuously ?
Answer:
Housekeeping genes

Question 7.
What type of RNAs do carry amino acids to the site of protein synthesis ?
Answer:
tRNA

Correct the sentences in each bit without changing the underlined words

Question 1.
Watson and Griffith proposed double helical structure of DNA.
Answer:
Watson and Crick proposed the double helical structure of DNA.

Question 2.
A nucleoprotein is building block of all nucleic acids.
Answer:
Nucleotides are the building blocks of all nucleic acids.

Question 3.
The strand of the DNA double helix represent nucleotide phosphate backbone and are antiparallel.
Answer:
The DNA double helix consist of a polynucleotide chain with a backbone formed of sugar and phosphate groups. These chains are antiparellel to each other.

Question 4.
The helical turns are right handed is Z DNA.
Answer:
The helical turns are left-handed in Z-DNA.

Question 5.
Avery, McCarty and MacLeod experimentally proved that the transforming principle is a protein.
Answer:
Avery, McCarty and MacLeod experimentally proved that transforming principle is DNA.

Question 6.
Meischer proposed the transforming principle.
Answer:
Frederick Griffith proposed the transforming principle.

Question 7.
The enzyme ligase is responsible for transcription.
Answer:
The enzyme DNA dependent RNA polymerase is responsible for transcription.

Question 8.
The operator is under the control of a repressor molecule synthesised by structural gene which is not a part of operon.
Answer:
The operator is under the control of a repressor molecule synthesised by regulator gene (i-gene) which is a part of operon.

Question 9.
The example of regulatory gene is genes of respiratory enzymes.
Answer:
The example of constitutive gene is genes of respiratory enzymes.

Question 10.
P-site in prokaryotes only accepts tRNA^met.
Answer:
P-site in prokaryotes only accepts tRNA f^met.

Question 11.
The coding or translatable sequences are introns.
Answer:
The intervening or non-coding sequences are introns.

Question 12.
The structural gens transcribe tRNA and rRNA.
Answer:
The structural gene do not transcribe tRNA and rRNA.

Question 13.
A primer is a small DNA or RNA strand hydrogen bonded to a template.
Answer:
A primer is a short strand of RNA or DNA that serves as a starting point for DNA synthesis.

Question 14.
In DNA replication, as per semiconservative model, two new strands synthesised, form new DNA molecules.
Answer:
In DNA replication as per semiconservative model, two parental strands would separate and act as a template for the synthesis of new complementary strands. Hence, a new strand consist of one parental strand and other new replicated strand.

Fill in the blanks

Question 15.
The enzyme …………. hydrolyses DNA molecules.
Answer:
exonucleases

Question 16.
Clover leaf model of fRNA was proposed by ………………
Answer:
Holey

Question 17.
The segment of DNA that expresses specific character is called …………..
Answer:
gene

Question 18.
The enzyme ………… helps to join nucleotides.
Answer:
ligase

Question 19.
The DNA strand which takes part in transcription is called ………………
Answer:
leading strand

Question 20.
UAG is …………. codon.
Answer:
stop

Question 21.
The gene which becomes active due to the presence of specific substance is called ………….. gene.
Answer:
inducible

Question 22.
To identify criminals DNA ………… is done.
Answer:
fingerprinting

Short Answer Type Questions

Write notes on the following with atleast 2 valid points

Question 1.
Inducible operon
Answer:
Inducible operon An inducible operon is an operon, in which the presence of a key metabolic substance induces transcription of the structural genes. One example of an inducible operon is lac operon and the inducer of this operon is lactose.

Question 2.
Repressible operon
Answer:
Repressible operon A repressible operon is an operon which always transcribes structural genes unless a repressor is present. One example of a repressible operon is trp operon.

Question 3.
Housekeeping genes
Answer:
House keeping genes are involved in basic cell maintenance and therefore are expected to maivlain constant constant expression levels in all cells and conditions. They are also called constituline gene

Question 4.
Adaptor molecules
Answer:
Adapter molecules tRNA acts as adapter molecules in translation. It serves as the physical link between the mRNA and the amino acid sequence of proteins. It carries an amino acid to the ribosome as directed by a three nucleotide sequence in a mRNA.

Question 5.
Split genes
Answer:
Split genes It is an interrupted gene that contains sections of DNA called exons which are expressed as RNA and proteins, interrupted by sections of DNA called introns, which are not expressed.

Question 6.
RNA splicing
Answer:
RNA splicing Splicing is the editing of the nascent precursor of mRNA transcript into a mature mRNA. After splicing, introns are removed and exons are joined together. The process of splicing involves two successive transesterification reaction. The RNA splicing is carried out with the help of a large complex called spliceosome.

Question 7.
Termination of translation
Answer:
Termination:
It is accomplished by the presence of any of the three termination codon on mRNA. Which are recognised by the release (termination) factor, RF₁, RF₂ and RF₃.

RF₁ and RF₂ They resemble the structure of tRNA. They compete with tRNA to bind the termination codon at A-site of ribosome. This is called molecular mimicry. RF₁ recognise UAG and RF₂ recognise UGA. UAA is recognised by both of them. RF₃ helps to split the peptidyl tRNA body by using GTP.
Note In eukaryotes, only one release factor is known. It iseRF₁.
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 1

Question 8.
Okazaki fragments
Answer:
Okazaki fragments During DNA replication, the new strand elongation occurs in opposite directions, as the two strands of the DNA are antiparallel.
On the leading strands, a continuous synthesis of new strand occurs while on the other strand (5′ → 3′ strand) discontinuous synthesis occurs. These discontinuous pieces of new DNA strands are called Okazaki fragments which join by DNA ligase to form the continuous strand

Question 9.
Central dogma
Answer:
Central Dogma:
It was proposed by Francis Crick (in 1958). According to the central dogma in molecular biology, the flow of genetic information is unidirectional, i.e.
DNA → RNA → Protein.
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 2
Central dogma
But later in 1970, HM Temin reported that the flow of information can be in reverse direction also, i.e. from RNA to DNA in some viruses (e.g. HIV) which is called as reverse transcription.

Modified central dogma

Note: Eukaryotic gene expressions were obtained from yeast,
Arabidopsia thaliana with developed techniques.

Differentiate with atleast 2 valid points

Question 1.
Genes and Chromosomes.
Answer:
Differences between genes and chromosomes are as follows

Genes	Chromosomes
Gene is a segment of DNA on the chromosome that codes for a functional protein and RNAs like tRNA, rRNA or ribozymes.	Chromosome is the structure formed by the condensation of chromatin during cell division.
Genes basically refers to the DNA fragment that directs the synthesis of a protein.	Chromosome consists of long DNA strand wrapped around histone proteins.
Gene contain coding sequence called exons and non-coding sequence called introns on the chromosome that directs synthesis of a protein.	Chromosome is a long DNA strand containing bdth coding (genes) and non-coding DNA (junk DNA or spacer DNA) between genes.

Question 2.
DNA and RNA.
Answer:
Differences between DNA and RNA are as follows

DNA	RNA
It is mainly confined to the nucleus, but also occurs in mitochondria and chloroplasts in small amount.	It mainly occurs in the cytoplasm. A small quantity is found in the nucleus.
It contains deoxyribose.	It contains ribose sugar.
It pyrimidines are cytosine and thymine.	Its pyrimidines are cytosine and uracil.
It consists of two polynucleotide chains held together by hydrogen bonds and coiled into a double helix. Some viruses (ϕ x 174) have single- stranded DNA.	It consists of a single polynucleotide chain. It may fold on itself and get hydrogen bonded and coiled into a pseudohelix. Some viruses (reovirus) have double-stranded RNA.

Question 3.
Purines and Pyrimidines.
Answer:
Differences between purines and pyrimidines are as follows

Purines	Pyrimidines
It contains two carbon-nitrogen rings and four nitrogen atoms.	It contains one carbon nitrogen ring and two nitrogen atoms.
Purines are adenine and guanine	Pyrimidines are cytosine, thymine and uracil.
120.11 g mol molar mass	80.088 g mol<sup>-1</sup> molar mass.

Question 4.
Exons and Introns.
Answer:
Differences between exons and introns are as follows

Exons	Introns
These are the nucleotide sequence of genes that are expressed and those are found at either sides of an intron.	These are sequences of nucleotides present in the genes between exons.
These are nucleotide sequences which code for proteins.	These are nucleotide sequences do not code for proteins.
These are translated regions on mRNA.	These are untranslated regions on mRNA.
After RNA splicing, only exons are present on the mature mRNA.	These are removed from mRNA during RNA splicing.

Question 5.
B-DNA and Z-DNA.
Answer:
Differences between B-DNA and Z-DNA are as follows

B-DNA	Z-DNA
It is with a right-handed type of helix.	It is with a left-handed type of helix.
Its helical diameter is 2.37 nm.	Its helical diameter is 1.84 nm.
It has 0.34 nm rise per base pair.	It has 0.37 nm rise per base pair.
It has 3.4 nm distance per complete turn.	It has 4.5 nm distance per complete turn.
Number of base pair per complete turn are 10.	Number of base pair per complete turn are 12.

Question 6.
Answer:
Replication and Transcription.
Answer:
Differences between replication and transcription are as follows

Replication	Transcription
It occurs in the S-phase of cell cycle.	It occurs in the G<sub>1</sub> and G<sub>2</sub> phases of cell cycle.
It is catalysed by DNA polymerase enzyme.	It is catalysed by RNA polymerase enzyme.
Deoxyribonucleoside triphosphate (dATP, dGTP, dTTP) serve as raw materials.	Ribonucleoside triphosphate (ATP, UTP, GTP, CTP) serve as raw materials.
Replication occurs along the strands of DNA.	IT takes place along one strand of DNA.
It involves unwinding and splitting of the entire DNA molecule.	It involves unwinding and splitting of only those genes which are to be transcribed.
It involves copying of the entire genome.	It involves copying of certain individual genes only.
Two double-stranded DNA molecules are formed from one DNA molecule.	A single one-stranded RNA molecule is formed from a segment of one strand.
Serve to conserve the genome for the next generation of cells and individuals.	Serve to form DNA copies of individual genes for immediate use in protein synthesis.
It require RNA primer to start replication.	No primer is required to start.
It produces normal DNA molecules that do not need	It produces primary RNA transcript molecules which need processing to acquire final form and size.

Question 7.
Transcription and Translation.
Answer:
Differences between transcription and translation are as follows

Transcription	Translation
It is the formation of RNA from DNA.	It is the synthesis of polypeptide over ribosome.
The template is antisense strand of DNA.	The template is mRNA.
It occurs inside the nucleus in eukaryotes and cytoplasm in prokaryotes.	It occurs in cytoplasm.
The raw materials are four types of ribonucleoside triphosphates – ATP, GTP, CTP and UTP.	The raw materials are 20 types of amino acids.
It forms three types of RNAs, i.e. rRNA, tRNA and mRNA	All the three types of RNAs take part in translation.
Transcription requires RNA polymerases and some transcription factors.	Translation requires initiation, elongation and releasing factors.
Polymerase moves over the template DNA.	Ribosome moves over mRNA.
An adapter molecule is not required.	Adaptor molecules bring amino acids over the template.
Product often requires splicing.	Splicing is absent.

Question 8.
Housekeeping gene and Inducible gene.
Answer:
Differences between housekeeping gene and inducible gene are as follows

Housekeeping gene	Inducible gene
These genes are constantly expressing themselves in a cell because their products are required for the normal cellular activities, e.g. genes for glycolysis, ATPase.	These genes are switched on in response to the presence of a chemical substance or inducer which is required for the functioning of the product of gene activity, e.g, nitrate for nitrate reductase.

Question 9.
Degenerate codon and Nonsense codon.
Answer:
Differences between degenerate codon and nonsense codon are as follows

Degenerate codon	Nonsense codon
Genetic code is degenerate for a particular amino acid, that is more than one codon can code for a single amino acid.	A codon for which no normal tRNA molecule exists does not code for any amino acid.
These codon causes translation.	The presence of nonsense codon causes termination of translation ending polypeptide synthesis chain.
These are many e.g. phenylalanine has two Codon is UAA and UUC.	These are three nonsense codons and are called amber(UAG), ochre(UAA) and opal(UGA).

Long Answer Type Questions

Question 1.
Give the structure of DNA. Add a note on different forms of DNA.
Answer:
Primary Structure of DNA:
Two nucleotides when linked through a 3′-5′ phosphodiester linkage, form a dinucleotide. The phosphodiester linkage is formed when each phosphate group esterifies to the 3′ hydroxy group of a pentose and to the 5′ hydroxyl group of the next pentose.

In a similar fashion, more nucleotides may join to form a polynucleotide chain (fig. structure of DNA). The polymer chain thus, formed has
(i) One end with a free phosphate moiety at 5′ end of deoxyribose sugar. This is marked as 5′ end of polynucleotide chain.
(ii) The other end with a free hydroxyl 3′-OH group marked as 3′ end of the polynucleotide chain.
Thus, the sugar and phosphates form the backbone in a polymer chain and the nitrogenous bases linked to sugar moiety project from this backbone. In RNA, there is an additional -OH group at 2′ position in the ribose of every nucleotide residue.
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 4

Secondary Structure of DNA:
Watson and Crick proposed the secondary structure in the form of the famous double helix model in 1953 on the basis of following observations
1. Erwin Chargafif (in 1950) formulated important generalisation on the base and other contents of DNA, called as ChargafFs rule. It states that for a double-stranded DNA, the ratios between adenine (A) and thymine (T) and guanine (G) and cytosine (C) are constant and equal to one.
i.e. $\frac{A + T}{G + C}$ = 1

2. X-ray diffraction studies by Wilkins in 1952, suggested a helicoidal configuration of DNA.

One of the important features of this model was the complementary base pairing. It means if the sequence of bases in one strand is known, the sequence in other strand can be easily predicted. Also, if each strand from a DNA acts as a template for synthesis of a new strand, the daughter DNA thus produced would be identical to the parental DNA molecule.

Watson and Crick Model of DNA:
Watson and Crick worked out the first correct double helix model of DNA, which explained most of its properties.
The salient features of double helix structure of DNA are as follows
(i) DNA is made up of two polynucleotide chains. The backbone is constituted by sugar phosphate, while the nitrogenous bases project inwards.
(ii) The two chains have anti-parallel polarity, i.e. when one chain has 3′ → 5′ polarity, the other has 5′ → 3′ polarity. Hence, orientation of deoxyribose sugar is opposite in both the strands.
(iii) The two strands are complementary to each other, i.e. purine base of one strand has pyrimidine counterpart on other strand. The complementary bases in two strands are paired through hydrogen bonds (H-bonds) to form base pairs.
(a) Adenine is bonded with thymine of the opposite strand with the help of two hydrogen bonds.
(b) Guanine is bonded with cytosine of the opposite strand with the help of three hydrogen bonds. So, a purine bonds with a pyrimidine always. Thus, maintaining a uniform distance between the two strands of the helix.
(iv) The two polypeptide chains are coiled in a right-handed fashion. Pitch of the helix, i.e. length of DNA in one complete turn = 3.4 nm or
3.4 × 10^-9 or 34 Å.
Number of base pairs in each turn = 10. Distance between a base pair in a helix = 0.34 nm. The diameter of DNA molecule is 20 Å (2nm).
(v) Percentage calculation of bases is done by
A + T = 100 – (G + C).
(vi) The plane of one base pair stacks over the other in double helix. This provides the stability to the helical structure, in addition to H-bond.
The length of DNA in E. coli is 1.36 mm, while in humans it is 2.2 m.
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 5
Structure of DNA : (a) Watson and Crick model of double helix, (b) Double-stranded polynucleotide chain sequence showing hydrogen bonds

Structural Forms of the Double Helix:
Double helical DNA exists in three structural forms namely the A-form DNA, the B-form DNA (described by Watson and Crick) and the Z-form DNA. The transition among these three forms plays an important role in the regulation of gene expression.
(i) B-DNA It is right-handed helix, contains 10 residues per 360° turn.

The planes of bases are perpendicular to the helix axis.
It is primarily found in chromosomal DNA.

(ii) A-DNA

It is formed by the moderate dehydration of B-DNA.
It is right-handed helix, contains 11 base pairs (residues) per 360° turn.
The planes of bases are tilted 20° away from the perpendicular to helical axis.
It is mainly found in DNA-RNA hybrid or RNA-RNA double-stranded regions.

(iii) Z-DNA It has zig-zag backbone and hence has the name.

It is a left-handed helix, twelve base pairs are present per turn.
The Z-DNA stretches occurring naturally in DNA have a sequence of alternating purines and pyrimidines (i.e. poly GC regions).
Besides these three major forms, the other two right-handed forms are
- C-DNA with nine base pairs per turn.
- D-DNA with eight base pairs per turn. There are many forms of DNA molecules in viruses.

Various Forms of DNA Molecules Found in a Variety of Viruses
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 7

Question 2.
Describe the semiconservative model of DNA replication.
Answer:
DNA Replication
In addition to the double helical structure of DNA, Watson and Crick also proposed a scheme for DNA replication. According to this model, the two strands of double helix separate and act as a template for the synthesis of new complementary strands in which the base sequence of one strand determines the sequence on the other strand.

This is called base complementarity and it ensures the accurate replication of DNA. After the completion of replication, each DNA molecule have one parental and one newly synthesised strand.
This scheme for DNA replication was termed as semiconservative DNA replication.

DNA Replication is Semiconservative:
Matthew, Meselson and Franklin Stahl in 1958 conducted an experiment in California Institute of technology with Escherichia coli to prove that DNA replicates semiconservatively as follows

1. They grew many generations of E.coli in a medium containing ¹⁵NH₅Cl (¹⁵N is the heavy isotope of nitrogen) as the only source of nitrogen.
The result was that ¹⁵N got incorporated into the newly synthesised DNA after several generations. By centrifugation in a cesium chloride (CsCl) density gradient, this heavy DNA molecule could be distinguished from the normal DNA.

2. The bacterial culture was then washed to make the medium free and the cells were then transferred into a medium containing normal ¹⁴NH₄Cl.

3. The samples were separated independently on CsCl gradient to measure the densities of DNA.

4. At definite time intervals, as the cells multiplied, samples were taken and the DNA which remained as double-stranded helices was extracted.

5. The DNA obtained from the culture, one generation after the transfer from ¹⁵N to ¹⁴N medium (i.e. after 20 minutes because E.coli divides in 20 minutes) had a hybrid or intermediate density.
This hybrid density was the result of replication in which DNA double helix had separated and the old strand (N¹⁵) had synthesised a new strand (N¹⁴).

6. The DNA obtained from the culture after another generation (II generation) was composed of equal amounts of hybrid DNA containing (N¹⁵ molecule) and ‘light’ DNA (containing 4 N molecule).

7. With the preeceding growth generations in normal medium, more and more light DNA was present. Hence, the semiconservative mode of DNA replication was confirmed.
CHSE Odisha Class 12 Biology Solutions Chapter 7 Molecular Basis of Inheritance 8
Meselson-Stahl experiment to demonstrate semiconservative replication

were conducted by Taylor and colleagues in 1958, involving use of radioactive thymidine, i.e. bromodeoxy-uridine. The replicated chromosomes were then, stained with fluorescent dye and Giemsa. The old and new strand were stained differently which confirm that the DNA in chromosomes also replicates semiconservatively.

Question 3.
Give evidences of DNA as genetic material.
Answer:
DNA as Genetic Material:
The discovery of nuclein by Meischer and the proposition of principal of inheritance by Mendel were almost at the same time, i.e. 1869 and 1866, respectively. But the fact that DNA acts as a genetic material took a long time to be discovered and proven.

By 1926, the quest to determine the mechanism for genetic inheritance had reached the molecular level and gradually the question, what molecule acts as genetic material got answered.

Transforming Principle:
Frederick Griffith in 1928, carried out a series of experiments with Diplococcus pneumoniae (a bacterium that causes pneumonia). He observed that when these bacteria were grown on a culture plate, some of them produced smooth, shiny colonies (S-type), whereas the others produced rough colonies (R-type).

This difference in appearance of colonies (smooth/rough) is due to the presence of mucous (polysaccharide) coat on S-strains (virulent/pathogenic) but not on R-strains (avirulent/non-pathogenic).

Experiment:

He first infected two separate groups of mice. The mice that were infected with the S-strain (S-III) died from pneumonia as S-strains are the virulent strains causing pneumonia.
The mice that were infected with the R-strain (R-II) did not develop pneumonia and they lived.
In the next set of experiments, Griffith killed the bacteria by heating them. The mice that were injected with heat-killed S-strain bacteria did not die and lived.
Whereas, on injecting a mixture of heat-killed S-strain and live R-strain bacteria, the mice died. Moreover, living S-bacteria were recovered from the dead mice.
These steps are summarised below

From all these observations Griffith concluded that the live R-strain bacteria, had been transformed by the heat-killed S-strain bacteria, i.e. some ‘transforming principle’ had transferred from the heat-killed S-strain, which helped the R-strain bacteria to synthesise a smooth polysaccharide coat and thus, become virulent.

This must be due to the transfer of the genetic material. However, he was not able to define the biochemical nature of genetic material from his experiments.

Biochemical Characterisation of Transforming Principle:
Oswald Avery, Colin MacLeod and Maclyn McCarty (1933-44) worked in Rockfellar Institute, New Xork, USA to determine the biochemical nature of ‘transforming principle’ in Griffith’s experiment in an in vitro system. Prior to this experiment, the genetic material was thought to be protein.

During this experiment, purified biochemicals (i.e. proteins, DNA, RNA, etc.) from the heat-killed S-III cells were taken, to observe which biochemicals could . transform live R-cells into S-cells.

They discovered that DNA alone from heat-killed S-type bacteria caused the transformation of non-virulent R-type bacteria into S-type virulent bacteria.
They also discovered that protein digesting enzymes (proteases) and RNA digesting enzymes (ribonuclease) did not inhibit this transformation. This proved that the ‘transforming substance’ was neither protein nor RNA.

DNA-digesting enzyme (deoxyribonuclease) caused inhibition of transformation, which suggests that the DNA caused the transformation. This provided the first evidence for DNA as transforming principle or the genetic material.

The steps of this experiment are summarised below:

R-II + DNA extract of S-III + no enzyme = R-II colonies + S-III colonies
R-II + DNA extract of S-III + Ribonuclease = R-II colonies + S-III colonies
R-II + DNA extract of S-III + Protease = R-II colonies + S-III colonies
R-II + DNA extract of S-III + Deoxyribonuclease = Only R-II colonies

Question 4.
Explain the mechanism of translation in prokaryotes.
Answer:
Mechanism of Translation:
The main steps in translation include
(i) Binding of iwRNA to ribosome
(ii) Activation of amino acids (aminoacylation of rRNA).
(iii) Transfer of activated amino acids to rRNA.
(iv) Initiation of polypeptide chain synthesis.
(v) Elongation of polypeptide chain.
(vi) Termination of polypeptide chain formation.

(i) Binding of mRNA to Ribosome
Ribosomes occur in the cytoplasm as separate smaller and larger units.
In prokaryotes, IF-3 binds to 30 S subunit to prevent association of subunits. The incoming tRNA containing specific amino acid binds to the A-site. The prokaryotic mRNA has a leader sequence called shine-Delgarno sequence that is present just prior to initiation codon-AUG.

It is homologous to 3′ end of 16S rRNA (ASD region) in 30S subunit. This complementarity ensures correct binding of 30S subunit on mRNA. The peptidyl mRNA containing elongating polypeptide then binds to P-site.
The bacterial ribosome contains another site, the E-site or Exit-site to which the discharged tRNA or tRNA whose peptidyl has already been transferred binds before its release from ribosome.
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A bacterial ribosome with three sites; E, exit site, P, peptidyl site and A, aminoacyl site

(ii) Aminoacylation
Aminoacylation of tRNA The activation of amino acids takes place through their carboxyl groups. The amino acids are activated in the presence of ATP and linked to their cognate tRNA. In the presence of ATP, amino acids become activated by binding with aminoacyl tRNA synthetase enzyme.
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The amino acid AMP-enzyme or AA-AMP enzyme complex is called an activated amino acid.
In the second step, this complex associated with the 3′-OH end of tRNA. AMP gets hydrolysed to form an ester bond between amino acid and tRNA and the enzyme is released.
AA – AMP – enzymes + tRNA ——– AA – tRNA + AMP + enzyme.

(iii) Transfer of Activated Amino Acids to tRNA:
The amino acids are attached to the tRNA by high energy bonds. These bonds are formed between the carboxyl group of amino acid and 3′ hydroxy terminal of ribose of terminal adenosine of CCA and of tRNA.
The complete reaction is carried out by enzyme synthetase which has two active sites, i.e. one for rRNA and another for specific amino acid molecule.

(iv) Initiation of Polypeptide Chain Synthesis:
The protein synthesis begins from the amino terminal end of the polypeptide, proceeds by the addition of amino acids through peptide bond formation and ends at the carboxyl terminal end. In prokaryotes, the initiation amino acid is formylated methionine while in eukaryotes it is methionine.
Initiation in Prokaryotes
In prokaryotes, two types of tRNA are present for methionine

tRNAf^met for initiation carrying formyl methionine and
tRNA^met for carrying normal methionine to growing polypeptide.

The initiation of polypeptide synthesis requires the following components
mRNA, 30S subunit of ribosome, formylmethionyl-tRNA (f^met– tRNAf^met), initiation factors IF-1, IF-2 and IF-3, GTP, 50S ribosomal subunit and Mg⁺².

The sequence of events occurring during initiation process are

1. The smaller 30S subunit of ribosome binds to the transcription factor IF-3. It prevents the premature association of two ribosomal subunits.

2. Interaction of SD region of mRNA and ASD region of ribosome helps the mRNA to bind to 30S subunit. It also helps AUG to correctly positioned at the P-site of the ribosome.

3. The fMet-tRNAf^met (the specific tRNA aminoacylated to formyl methionine) binds to the AUG codon at the P-site. The tRNAf^met is the only tRNA that binds to its codon present on the P-site. All other tRNA along with their respective amino acids bind to their codon present at the A-site. Therefore, AUG codon present as initiation codon codes for formylmethionine. When it is present at other position it codes for normal methionine.

4. The initiation factor IF-1, binds to the A-site. It prevents the binding of any other aminoacyl tRNA to the codon at the A-site during initiation.

5. The GTP bound IF-2 (GTP-IF-2) and the initiating f Met-tRNAf^met attaches to the complex of 30S subunit-IF3-IF1-mRNA.

6. 50S subunit then attaches the complex formed in the previous step. The GTP bound to IF-2 is hydrolysed to GDP and Pi. After this step, all the three initiation factors leave ribosome. This complex of 70S ribosome, mRNA and f Met-tRNA f^met bound to initiation codon at P site is known as initiation complex.
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Stepwise formation of initiation complex in prokaryote

(v) Elongation of Polypeptide Chain:
In this step, another charged aminoacyl tRNA complex binds to the A-site of the ribosome, following the hydrolysis of GTP to GDP and Pi. A peptide bond forms between carboxyl group (—COOH) of amino acid at P-site and amino group (—NH₃) of amino acid at A-site by the enzyme peptidyl transferase.
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Binding of the second aminoacyl tRNA to the A site of ribosome

Formation of a peptide bond

(vi) Translocation of Polypeptide:
The peptidyl fRNA bounded to A-site comes to the P-site of ribosome.
The empty tRNA comes to E-site and a new codon occupies the A-site for next aminoacyl tRNA.

This is achieved by the movement or translocation of ribosome by a codon in 5′ to 3′ direction of mRNA in the presence of EF-G (translocase) and GTP.
tRNA interact with E-site on 50S subunit through it CCA sequence at 3′ end.

The tRNA molecule is then, transferred from A site to P-site and from P-site to E-site by the movement of two subunits of ribosomes.
Finally, the deacylated tRNA is released to cytosol from E-site.
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(vii) Termination:
It is accomplished by the presence of any of the three termination codon on mRNA. Which are recognised by the release (termination) factor, RF₁, RF₂ and RF₃.

RF₁ and RF₂ They resemble the structure of tRNA. They compete with tRNA to bind the termination codon at A-site of ribosome. This is called molecular mimicry. RF₁ recognise UAG and RF₂ recognise UGA. UAA is recognised by both of them. RF₃ helps to split the peptidyl tRNA body by using GTP.
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Question 5.
Describe transcription in prokaryotes.
Answer:
Transcription in Prokaryotes:
All three RNAs are needed for synthesis of a protein in a cell. DNA dependent RNA polymerase is the single enzyme that catalyses the transcription of all types of bacterial RNA. But for the expression of different genes, different sigma factors may associate with same core enzymes.

In E.coli, σ⁷⁰ is used in normal condition σ³² / σ^H under heat shock, σ⁵⁴ /σ^N under nitrogen starvation and σ²⁸ for chemotaxis.
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A typical bacterial transcription unit

The transcription process in prokaryotes occurs in following steps
I. Initiation

The holoenzyme binds to the promoter region of transcription unit.
The sigma polypeptide binds loosely to the promoter sequences so as to form a loose, closed, binary complex.
It is followed by the formation of a transcription eye or bubble due to the denaturation of adjacent sequence of DNA, lying next to the complex.
The transcription bubble along with the bounded holoenzyme is called open binary complex.
In 90% of cases, the start point of transcription is a purine.
At the elongation site of enzyme, two nucleotides complementary to the first two nucleotides of template strand binds.
A phosphodiester bond is formed between these two ribonucleotides.
At this stage, the complex is called ternary complex that consists of partly denatured DNA bounded with holoenzyme having a di-ribonucleotide.
The same process continues till a RNA chain of about nine nucleotides is synthesised. The holoenzyme does not move throughout this process.
After the completion of initiation process, sigma factor dissociates from RNA polymerase. This facilitates the promoter clearance so that a new holoenzyme can bind to promoter for second round of transcription.

Binding of RNA polymerase and initiation of RNA synthesis

II. Elongation

The RNA chain grows in 5′-3′ direction by the addition of ribonucleotides to the 3′-end of RNA.
The transcription bubble moves in 3′ → 5′ direction of template strand.
The movement of holoenzyme along the bubble unwinds (denature) the DNA in growing point and rewinds at the opposite end.
In each elongation cycle, the growing site (leading product) of enzyme gets filled with 10 newly added nucleotides. The opposite site (lagging product) contains the previous segment of RNA.
About 40 nucleotides are added per 37°C.
In some phages, e.g. T₃ and T₄, RNA pol synthesise RNA at much rapid rate of about 200 nucleotides per 37° C.

Elongation of RNA chain by the movement of RNA polymerase and transcription bubble in 5′ to 3′ direction

III. Termination
It is achieved by certain termination signals on DNA called terminators. In E.coli, terminators are of two types

(a) Intrinsic Terminators

These are rho independent protein factors in which the RNA at 3′-end contains a long stretch of U residues.
These residues are hydrogen bonded to the long stretch of A residues of the temple. In the stem of the RNA, a stretch of G-C rich segment is present which results in a hair-pin loop formation in the RNA stem.
Due to the weak association between A-U base pairs, the long stretch of termination sequence break and the RNA is released.
It occurs due to the formation of hair-pin loop in the stem of RNA before the termination signal slows down transcription and as a result dA-rU bonds break at any one point so as to release RNA from RNA-DNA hybrid.

(b) Extrinsic Terminator

These are rho dependent protein factors and are extensively used in E. coli.
This protein is active as an hexamer (having six identical subunits). Its molecular weight is about 46,000 and it also has ATP hydrolysing activity.
To terminate the process of transcription, rho factor binds to the 5′-end of nascent mRNA and moves along the length of mRNA until it reaches the termination point. Due to this, the transcription process slows down, rho breakdown ATP and utilises the energy to denature the RNA-DNA hybrid. Hence, the RNA is released from the bubble.

In prokaryotes (bacteria), mRNA does not require any processing to become active and both transcription and translation take place in same compartment (as there is no separation of nucleus and cytosol in bacteria). Therefore, translation can start much before the mRNA is fully transcribed, i.e. transcription and translation can be coupled.

Question 6.
Give an account of the operon model.
Answer:
The Operon Model:
F Jacob and J Monod gave the operon concept and were the first ones to describe a transcriptionally regulated system. An operon is a unit of prokaryotic gene expression which includes sequentially regulated (structural) genes and control elements recognised by the regulatory gene product. The various components of an operon are

Structural genes These are the regions of DNA which transcribe wRNA for polypeptide synthesis.
Promoter gene This is the sequence of DNA where RNA polymerase binds and initiates transcription.
Operator This is the sequence of DNA found adjacent to promoter where specific repressor protein binds. It is under the control of a repressor.
Regulator It is the gene which codes for the repressor protein binding to the operator and suppresses its activity, so that transcription does not occur. It is also represented as ‘i’ gene. It is synthesised by a regulator gene which is not a part a operon.
Inducer Its main role is to prevent the repressor from binding to the operator. This makes the process of transcription to switch on. An inducer can be any metabolite, hormone, etc.

Loc Operon in E. coli:
The lac operon found in E.coli is an inducible system. It is responsible for the synthesis of enzymes found in lactose (the milk sugar). It has an operator sequence of 26 base pairs and three structural genes. Its first structural gene (SG) is lac Z which is of 3063 base pairs. It is responsible for the synthesis of the emzyme ß-galactosidase.
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The operator is a part of lac Z. The other two genes are lac y (helps in the synthesis of ß-galactoside permease) and lac a (synthesise fbgalactoside transacetylase). ß-galactoside permease is a transmembrane protein that pumps galactose into the cell, ß-galactosidase helps to breakdown lactose to galactose and glucose.

When lactose is available to the bacterium, the active repressor produced by the regulator forms an inactive dimer with lactose (acts as an inducer).

As a result, the inactive dimer cannot bind to the operator and the three contiguous structural genes are transcribed into a polycistronic or polygenic mRNA which is then translated into three proteins (enzymes). In the absence of lactose (the inducer), the product of regulator enzyme activates inhibitor dimer that, binds to the operator and prevents transcription.