CHSE Odisha Class 12 Biology Solutions Chapter 15 Ecosystem

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

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

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

1. Photoautotrophs They obtain energy from the sunlight by the process called photosynthesis, e.g. green plants, photosynthetic bacteria, etc.
2. 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

1. Primary consumers They directly consume the organic compounds synthesised by autotrophs, e.g. mammalian herbivores (predators), insect herbivores (parasites), etc.
2. 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

1. Species composition It is calculated by the identification and enumeration of plant and animal species of an ecosystem.
2. 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.

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

1. 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.
2. 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

1. Planktons and weeds in oceans About 50% of available oxygen is produced by planktons of marine ecosystem.
2. 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.