CHSE Odisha Class 12 Biology Important Questions Chapter 15 Ecosystem

Odisha State Board CHSE Odisha Class 12 Biology Important Questions Chapter 15 Ecosystem and Environment Important Questions and Answers.

CHSE Odisha 12th Class Biology Important Questions Chapter 15 Ecosystem

EcosystemClass 12 Important Questions CHSE Odisha

Very Short Answer Type Questions

Choose the correct option

Question 1.
Biotic components include
(a) producers, consumers and decomposers
(b) producers and consumers
(c) Both (a) and (b)
(d) None of the above
Answer:
(a) producers, consumers and decomposers

Question 2.
The non-green plants are as important as green plants because they
(a) cause human diseases
(b) cause diseases of other plants
(c) are useful in several industries
(d) bring about decomposition of dead animal and plant remains
Answer:
(d) bring about decomposition of dead animal and plant remains

Question 3.
Primary consumers are always
(a) producers
(b) carnivores
(c) herbivores
(d) omnivores
Answer:
(c) herbivores

Question 4.
Man is ………… .
(a) herbivorous
(b) carnivorous
(c) omnivorous
(d) producers
Answer:
(c) omnivorous

Question 5.
Secondary producers are
(a) herbivores
(b) producers
(c) carnivores
(d) None of these
Answer:
(d) None of these

Question 6.
Which of the following is an abiotic component of ecosystem?
(a) Bacteria
(b) Humus
(c) Plants
(d) Fungi
Answer:
(b) Humus

Question 7.
Decomposers are generally
(a) green plants
(b) phytoplanktons
(c) insects
(d) microorganisms
Answer:
(d) microorganisms

Question 8.
Abiotic components of an ecosystem include
(a) producers, consumers and decomposers
(b) producers and consumers
(c) only producers
(d) None of the above
Answer:
(d) None of the above

Question 9.
An ecosystem is not a /an
(a) open system
(b) closed system
(c) variable system
(d) None of the above
Answer:
(b) closed system

Question 10.
Trophic levels in ecosystem are formed by
(a) only bacteria
(b) only plants
(c) only herbivores
(d) organisms linked in food chain
Ans.
(d) organisms linked in food chain.

Question 11.
Detritus food chain begins with
(a) virus
(b) bacteria
(c) protozoan
(d) algae
Answer:
(b) bacteria

Question 12.
Which one of the following has the largest population in food chain?
(a) Producers
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers
Answer:
(d) Decomposers.
As, they include microorganisms, they form largest population in a food chain and decompose dead plants and animals.

Question 13.
The second trophic level in a lake is ………….. .
(a) phytoplanktons
(b) zooplanktons
(c) benthos
(d) fishes
Answer:
(b) Zooplanktons.
They are primary consumers in an aquatic food chain who feed upon phytoplanktons.

Question 14.
A food chain can have trophic levels
(a) one
(b) two
(c) three
(d) multiple
Answer:
(d) multiple

Question 15.
Who proposed the concept of ecological pyramid?
(a) Odum
(b) Elton
(c) Tansley
(d) Clements
Answer:
(b) Elton.

Question 16.
Primary succession is development of communities on
(a) cleared forest area
(b) newly exposed habitat
(c) pond filled after a dry season
(d) freshly harvested crop field
Answer:
(b) newly exposed habitat

Question 17.
Lichen is pioneer in which succession?
(a) Hydrosere
(b) Lithosere
(c) Psammosere
(d) Halosere
Answer:
(b) Lithosere

Question 18.
Plant succession in a saline habitat is called
(a) hydrosere
(b) halosere
(c) psammosere
(d) xerosere
Answer:
(b) halosere

Question 19.
The first species that establishes itself in a barren habitat due to succession is called
(a) climax
(b) migrant
(c) colony
(d) pioneer
Answer:
(d) pioneer

Question 20.
When propagating units like seeds and spores enter a barren area to initiate the process of succession, it is called
(a) nudation
(b) reaction
(c) ecesis
(d) migration
Answer:
(c) ecesis

Question 21.
The rate of release of nutrients into atmosphere is regulated by
(a) temperature
(b) soil nature
(c) pH
(d) All of the above
Answer:
(d) All of the above

Question 22.
Weathering of rocks makes phosphorus available first to
(a) producers
(b) decomposers
(c) consumers
(d) None of the above
Answer:
(a) producers

Fill in the blanks

Question 1.
Plants are called as ……….. because they fix carbon dioxide.
Answer:
autotrophs

Question 2.
In an aquatic ecosystem, the limiting factor for the productivity is …….. .
Answer:
sunlight

Question 3.
Decomposers are generally ……… (green plants, microorganisms, phytoplanktons, insects)
Answer:
microorganisms

Question 4.
A detrivore is animal feeding on …………… .
Answer:
dead matter

Question 5.
Productivity is expressed in terms of …………… .
Answer:
g^-2 yr^-1 (kcal m^-2)yr^-1

Question 6.
Amount of energy transferred from one trophic level to next is ………. .
Answer:
10%.

Question 7.
Tip of an ecological pyramid is occupied by ………. .
Answer:
carnivores.

Question 8.
In an ecosystem dominated by trees, the pyramid of number is ………. type.
Answer:
inverted.

Question 9.
Green plants constitute ………….. trophic level.
Answer:
First

Question 10.
………… represents sedimentary type of nutrient cycle.
Answer:
Phosphorus.

Question 11.
In ……….. succession, dominant organisms are autotrophs.
Answer:
autotrophic

Question 12.
The individual transitional communities are called ………. .
Answer:
serai

Correct the statement if required, by changing the underlined word

Question 1.
The term ecosystem was proposed by Odum.
Answer:
Tansley

Question 2.
The two components of an ecosystem are plants and animals.
Answer:
biotic and abiotic.

Question 3.
Carnivores are always primary consumers.
Answer:
Herbivores

Question 4.
The raw material for decomposition is called vermicompost.
Answer:
detritus

Question 5.
Net primary productivity is GPP + R.
Answer:
GPR-R

Question 6.
Out of the total solar energy, PAR is only 1-5%.
Answer:
50%

Question 7.
Phytoplanktons occupy more than one trophic level in pond ecosystem.
Answer:
Fishes.

Question 8.
Pyramid of energy is always inverted.
Answer:
upright.

Question 9.
Pyramid of energy is always inverted.
Answer:
Always upright

Question 10.
Flow of energy declines as it passes from lower to higher trophic level. This is explained by first law of thermodynamics.
Answer:
It is correct.

Question 11.
Plant succession in a sandy area is lithosere.
Answer:
psammosere

Question 12.
The pioneer community in hydrosere is submerged plants.
Answer:
phytoplanktons

Question 13.
Climate control comes under supporting ecosystem services.
Answer:
Primary productivity

Question 14.
The first species that establishes itself in a barren habitat due to succession is called migrant.
Answer:
pioneer species

Question 15.
Lichens and mosses are the part of halosere.
Answer:
xerosere

Express in one or two words

Question 1.
What is the creating force of an ecosystem?
Answer:
Solar energy.

Question 2.
What type of ecosystem is represented by pond?
Answer:
Freshwater ecosystem.

Question 3.
Name the common detritivores in an ecosystem.
Answer:
Earthworms

Question 4.
Name the two basic categories of an ecosystem.
Answer:
Natural and Artificial ecosystem

Question 5.
Name the largest decomposers of forest floor.
Answer:
Microorganisms

Question 6.
Name the term used for rate of storage of organic matter not used by heterotrophs.
Answer:
Gross primary productivity

Question 7.
Name any two organisms, which can occupy more than one trophic level in an ecosystem.
Answer:
Human beings and birds (e.g. sparrow).

Question 8.
State, what does standing crop of a trophic level represent?
Answer:
Standing crop represents total amount of living matter or organic matter present in an ecosystem in an unit area and at a specific time.

Question 9.
List any two ways of measuring the standing crop of a trophic level.
Answer:
Two ways of measuring the standing crop of a trophic level are

• Biomass of living organisms.
• Number in an unit area.

Question 10.
Expand PAR.
Answer:
Photosynthetically Active Radiation

Question 11.
What is the starting point of a grazing food chain and of a detritus food chain?
Answer:
Producers and dead organic matter, respectively.

Question 12.
Which is the major reservoir of carbon on earth?
Answer:
Ocean.

Question 13.
Under what conditions would a particular stage in the process of succession revert back to an earlier stage?
Answer:
Natural or human induced disturbances like fire, deforestation, etc.

Question 14.
Give one examples of xerarch succession.
Answer:
Sand deserts and rock deserts (as there is no water and the substratum does not absorb rainwater).

Question 15.
How much of carbon is dissolved in the oceans?
Answer:
71%

Question 16.
Name the two forms of reservoir of carbon, that regulate the ecosystem carbon cycle.
Answer:
ocean and fossil fuel

Question 17.
How much carbon is fixed in the biosphere through photosynthesis annually?
Answer:
4 × 10¹³ kg

Question 18.
What do you understand by the term serai stage?
Answer:
The individual transitional communities are termed as serai stage.

Short Answer Type Questions

Question 1.
Write a note on 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.

Question 2.
Is an aquarium a complete ecosystem?
Or
Can an aquarium be considered a complete ecosystem?
Answer:
Yes, aquarium is a man-made ecosystem (artificial). If an ecosystem possesses all physical and biological components, then it is said to be complete.
Since, aquarium has biotic components (plants and fishes) and abiotic components (air and water) required for survival of fishes so, it is a complete ecosystem.

Question 3.
Apart from plants and animals, microbes form a permanent biotic component in an ecosystem.
While plants have been referred to as autotrophs and animals as heterotrophs, what are microbes referred to as?
Or
How do these microbes fulfil their energy requirements?
Answer:
Microbes are referred to as heterotrophs and saprotrophs. They fulfil their energy requirement by feeding on dead remains of plants and animals through the process of decomposition.

Question 4.
How are productivity, gross primary productivity, net primary productivity and secondary productivity interrelated?
Answer:
A constant input of solar energy is the basic requirement’ for any ecosystem so that the living organisms can survive, grow (make new cells) and maintain their internal orgnisation. The rate of synthesis of energy containing organic matter or biomass per unit area in unit time is called its productivity. It is expressed in terms of g^-2yr^-1 or (kcal m^-2) yr^-1. Productivity of an ecosystem can be categorised as primary and secondary productivity.

Primary Productivity:
It is the amount of biomass or organic matter produced per unit area over a time period by plants due to photosynthesis. It is expressed in terms of weight (g^-2d^-1) or energy (kcal m^-2).
The primary productivity has two aspects as discussed below

Gross Primary Productivity (GPP):
It is the total amount of produced organic matter during photosynthesis. A considerable amount of GPP is utilised or lost by plants in respiration.

Net Primary Productivity (NPP)
It is the available biomass for the consumption by heterotrophs (herbivores and decomposers). It is actually the amount of energy left in the producers after the utilisation of some energy during respiration. Thus, Gross Primary Productivity (GPP) minus the Respiration Losses (R) gives the Net Primary Productivity.

GPP – R = NPP where, R = Respiration losses.
Net primary productivity differs in different communities of plants, e.g.

• In terrestrial community, GPP is 2.7 times of NPP.
• In ocean community, GPP is 1.5 times of NPP.

Secondary Productivity:
It is the rate of assimilation and formation of new organic matter by consumers. It is small as compared to primary productivity and tends to decrease with an increase in the trophic level.

Question 5.
Primary productivity varies from ecosystem to ecosystem. Explain.
Answer:
Primary productivity varies from ecosystem to ecosystem because it depends on the plant species inhabiting the area and their photosynthetic activity. It also depends on various environmental factors like-light, temperature, rain, etc., and nutrient availability which varies in different ecosystems.

Question 6.
(i) What is primary productivity? Why does it vary in different types of ecosystems?
(ii) State the relation between gross and net primary productivity.
Answer:
(i) RIt is the amount of biomass or organic matter produced per unit area over a time period by plants due to photosynthesis. It is expressed in terms of weight (g^-2d^-1) or energy (kcal m^-2).
Primary productivity varies from ecosystem to ecosystem because it depends on the plant species inhabiting the area and their photosynthetic activity. It also depends on various environmental factors like-light, temperature, rain, etc., and nutrient availability which varies in different ecosystems.

(ii) The relation between the gross and net primary productivity can be shown as P_n = P_g – R
where, P_n = Net Primary Productivity (NPP)
P_g = Gross Primary Productivity (GPP)
R = Respiration

Question 7.
Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer.
A young forest, a natural old forest, a shallow polluted lake, alpine meadow.
Answer:
Primary productivity can be defined as the rate at which primary producers (e.g. green plants) trap and store solar radiation in the form of biomass. This is measured in terms of weight (g^-2) and in terms of energy (kcal m^-2) per year in a given time. So, primary productivity varies from ecosystem to ecosystem and the ecosystem which possesses more producers will be more productive in terms of primary productivity.

So, young forests grow quicker than older mature forests and are more productive in terms of productivity.
The shallow polluted lake and alpine meadow will be less productive because of less number of producers and high amount of dead organic matter.

Question 8.
Why is the rate of assimilation of energy at the herbivore level called secondary productivity?
Answer:
The rate of assimilation of energy at herbivore (primary consumer) level is called secondary productivity because the biomass available to the organisms of this trophic level is a resultant of the primary productivity, which is formed by autotrophs (plants).

Question 9.
Why are oceans least productive?
Answer:
Oceans are least productive because

• there is insufficient radiation as sunlight decreases with the increasing depth of the ocean.
• oceans are nitrogen deficient which is an important nutrient for plants.
• conditions of high salinity in Ocean are not favourable for all plants.
• there is no substratum to support plants.

Question 10.
Write a note on decomposers.
Answer:
The microorganisms that breakdown the dead remains of plants, animals and organic matter into simpler inorganic substances are called decomposers.
These organisms are mainly aerobic and require oxygen-rich conditions to carry out their functioning. Their mode of nutrition is generally saprophytic as they ingest partially digested food material.

Question 11.
The rate of decomposition of detritus is affected by the abiotic factors like availability of oxygen, pH of the soil substratum, temperature, etc. Discuss.
Answer:
It is the process of breaking down of complex organic matter into inorganic substances like water, carbon dioxide and nutrients by decomposers. Detritus is the raw material for decomposition. It includes dead remains of plants (leaves, bark and flowers) and animals including faecal matter. Different steps involved in the process of decomposition are

1. Fragmentation It is the process of breakdown of detritus into smaller particles by detritivores (e.g. earthworm).
2. Leaching It is the process by which water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
3. Catabolism It is the process of degradation of detritus into simple organic material by the action of bacterial and fungal enzymes and then they are further converted into simpler inorganic compounds.
4. Humification It is a process that leads to the accumulation of a dark coloured amorphous and colloidal substance called humus. It is highly resistant to microbial action and undergoes decomposition at a very slow rate. Being colloidal in nature, it serves as a reservoir of nutrients.
5. Mineralisation It is the process of degradation of humus by microbial action and release of inorganic nutrients.

Some are eaten by insects and other animals. Nutrients and energy enter food web.

Diagrammatic representation of decomposition cycle in a terrestrial ecosystem

Question 11.
Justify the following statement in terms of ecosystem dynamics.
‘Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity.’
Answer:
Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. So, nature tends to increase gross primary productivity through supporting the large number of plants (producers) in an ecosystem.
Net primary productivity is the available biomass for the consumption by heterotrophs (human and animals).
Man tries to increase net primary productivity by cultivating food and other crops to fulfil their needs.

Question 12.
‘The energy flow in an ecosystem is unidirectional’. Justify the statement.
Answer:
Energy in an ecosystem flows from producers to primary consumers, then from primary consumers to secondary consumers and so on. There is never a backflow of energy, i.e. energy cannot come back to a trophic level it has already passed. Therefore, the energy flow is unidirectional in an ecosystem.

Question 13.
The diagram shows the flow of energy through an ecosystem.

Which arrows represent the smallest amount of energy transferred between organisms and the largest amount of energy lost to the ecosystem?
Answer:
The smallest amount of energy transferred is represented by arrow 2 and largest energy loss by arrow 3.

Question 14.
‘The energy flow in the ecosystem follows the second law of thermodynamics’. Explain.
Answer:
According to second law of thermodynamics, every activity involving energy transformation is accompanied by dissipation of energy as heat and increase in disorderliness, except in deep hydrothermal ecosystems.

This is because out of the total PAR only 2-10% is captured by photosynthetic organisms in synthesis of organic matter. Further, this energy is used during various metabolic processes for the formation of food and a very little is stored as biomass. This trapped energy as biomass is transferred to next trophic level according to Lindeman’s law. Only 10% of the stored energy is passed from one trophic level to successive trophic level.

Question 15.
Organisms at a higher trophic level have less energy available. Comment.
Answer:
Energy flow in the ecosystem follows the 10% energy flow law, proposed by Lindeman. According to this law, only 10% of the energy available at each trophic level, gets transferred to the next trophic level, the rest is lost in the environment as heat.

As we move to higher trophic levels, the energy available to organisms keeps on decreasing. Thus, the top . carnivore gains the least energy in a food chain.

Question 16.
The number of trophic levels in an ecosystem are limited. Comment.
Answer:
The number of trophic levels in an ecosystem are limited and are not more than 3-4. Because the amount of energy flow decreases with successive trophic level, as only 10% of energy is transferred from one trophic level . to the next trophic level.
So, rest of the energy is lost in the form of respiration and other vital activities to maintain life. If more trophic levels are present, the residual energy will be limited and will decrease to such an extent that it cannot further support any trophic level. So, the food chain is generally limited to 3-4 trophic levels only.

Question 17.
Write a short note on food chain.
Answer:
The transfer of energy from green plants through a sequence of organisms, in which each eats the one below it in the chain and is eaten by the one above is called a food chain. It is actually a feeding chain of organisms in an ecosystem.

Based on the relationship among the organisms and the source of their nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level. An assemblage of trophic levels within the ecosystem is known as trophic structure.
A single species may occupy multiple trophic levels in a food.
Example

• Grass → Grasshopper → Frog → Snake → Eagle.
• Grass → Goat → Man

Question 18.
Three food chains are shown below
(i) Grass → Deer → Tiger
(ii) Tree → Beetle → Bacteria
(iii) Flowering plant → Butterfly → Bird
They can be represented by the three pyramids of numbers P, Q and R below

Write the correct combination that correctly matches food chains and pyramids.
Answer:
P → 3, Q → 1, R → 2

Question 19
Define ecological pyramids and describe with examples, pyramids of number and biomass.
Or
Write a short note on ecological pyramids.
Answer:
Ecological pyramids are diagrammatic illustrations of connection between different trophic levels in terms of energy, biomass and number of organisms.
Pyramid of biomass can be both upright and inverted. This can be understood from the examples given below

1. The pyramid of biomass in a pond ecosystem is inverted. Because, the sum total of the weight of phytoplankton (producer) is far less than a few fishes feeding on them, at higher trophic levels.
2. Pyramid of biomass in a forest ecosystem is upright because producers are more in biomass than primary consumers. Primary consumers are more than secondary consumers and secondary consumers are more than tertiary consumers (top).

Pyramid of energy is never inverted (i.e. it is always upright). Because, when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step.
Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time.

Question 20.
Write a note on pyramid of energy.
Answer:
Pyramid of Energy
It represents the total amount of energy utilised by different trophic level organisms in unit area over a period of time.

An ideal pyramid of energy with primary producers storing only 196 of solar energy as NPP

Its unit is kj/ha/yr. Pyramid of energy is always upright, i. e. it can never be inverted, because when energy is transferred from a particular trophic level to the next trophic level, some energy is always lost as heat at each step. It is in accordance with the first law of thermodynamics which states that energy is always conserved, it is neither created nor destroyed.

Question 21.
Fill in the missing stages in the given primary hydrarch succession.
Phytoplankton → A → B → C → Submerged free-floating → D → Forest plant stage
Answer:
A – Reed-swamp stage
B – Submerged plant stage
C – Marsh-meadow stage
D – Shrub stage.

Question 22.
Mention the role of pioneer species in primary succession on rocks.
Answer:
Lichens are pioneer species in primary succession on rocks. They secrete organic acids, which wither the rock and help in soil formation. Lichens by forming soil pave way for the next community, i.e. bryophytes.

Question 23.
Write the notes on the following
(i) Define pioneer species.
(ii) Among bryophytes, lichens and fern, which one is a pioneer species in a xeric succession and why?
Answer:
(i) The species that invade a bare area are called pioneer species.
(ii) In a xeric succession, the pioneer species are usually lichens then bryophytes, which are succeeded by ferns and some other bigger plants.

Lichen produces lichen acid and carbonic acid which corrode rock surface and release minerals required for growth. The corroded rock accumulates soil particle by wind and provides substrate for bryophytes and ferns.

Question 24.
State the function of a reservoir in a nutrient cycle. Explain the simplified model of carbon cycle in nature.
Answer:
The function of reservoir is to meet the deficit which occurs due to imbalance in the rate of influx and efflux.

Question 25.
Why are nutrient cycles in nature called biogeochemical cycles?
Answer:
Nutrient cycles are called biogeochemical cycles because ions/molecules of a nutrient are transferred from the environment (rocks, air and water) to organisms (life) and then brought back to the environment in a cyclic pathway.
The literal meaning of biogeochemical is bio – living organism and geo – rocks, air and water.

Question 26.
Outline the salient features of carbon cycle in an ecosystem.
Answer:
Carbon constitutes 45% of dry weight of organisms and it is next only to water. About 71% carbon is found dissolved in oceans. This oceanic reservoir regulates the amount of carbon dioxide (CO₂) in the atmosphere. The fossil fuels also represent a reservoir of carbon.Therefore, carbon cycling occurs through atmosphere, ocean and through living and dead organisms.

Approximately, 4 × 10¹³ kg of carbon is fixed in the biosphere through photosynthesis annually. Carbon-fixation or carbon assimilation refers to the conversion process of inorganic carbon (carbon dioxide) into organic compound. CO₂ is returned to the atmosphere via respiratory activities of producers and consumers. Decomposers also contribute substantially to CO₂ pool by their processing of waste materials and dead organic matter of land or oceans.

Various activites like burning of wood, forest fire and cqmbustion of organic matter, fossil fuels and volcanic eruption contributes to additional sources of CO₂ release into the atmosphere.
Human activities have significantly influenced the carbon cycle, e.g. rapid deforestation and burning of fossil fuel for energy and transport have significantly increased the rate of release of carbon dioxide into the atmosphere.

Question 27.
Complete the following model of carbon cycle by filling A, B, C, D, E and F.

Answer:
A – Respiration,
B – Photosynthesis,
C – Respiration,
D – Combustion of fossil fuels
E – Aquatic food chain and
E – Coal and oil.

Question 28.
Write important features of a sedimentary cycle in an ecosystem.
Answer:
Phosphorus cycle is an example of sedimentary nutrient cycle, since, it moves from land to the sediments at the bottom of the seas, then back to land again. The natural reservoir of phosphorus is earth’s crust. Rocks contain phosphorus in the form of phosphates.

By weathering and soil erosion, phosphates enter streams, rivers and then to oceans. With great movements of the tectonic plates, sea floor is uplifted and phosphates become exposed to the drained land surfaces. From here, weathering for a long period of time releases phosphates from rocks. Minute amount of these phosphates dissolve in soil and are absorbed by the roots of the plants. Herbivores and other animals obtain this element from the plants.

Question 29.
Describe the advantages for keeping the ecosystems healthy.
Or
Write a short note on ecosystem services.
Answer:
The various benefits that humans obtain from the ecosystem are collectively called ecosystem services.
The advantages of keeping an ecosystem healthy can be grouped into following types

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.

Differentiate between the following (for complete chapter)

Question 1.
Standing crop and Standing state.
Answer:
Differences between standing crop and standing state are as follows

Standing crop	Standing state
It is amount of biomass present in an ecosystem.	It is amount of inorganic nutrients found in an ecosystem.
It represents the entire living matter.	It represents a part of non-living matter.
There is no circulation of this matter.	It circulates between living and non-living components of the ecosystem.
Continuous synthesis and consumption of biomass goes on.	It is being regularly depleted and replenished by the living matter.

Question 2.
Primary productivity and Secondary productivity.
Answer:
Differences between primary productivity and secondary productivity are as follows

Primary productivity	Secondary productivity
It is the rate of synthesis of organic matter by producers.	It is the rate of synthesis of organic matter by consumers.
It is comparatively quite high.	It is small and decreases with rise of trophic level.
It is due to synthesis of fresh organic matter from inorganic raw materials.	It is due to synthesis of organic matter from organic matter.

Question 3.
Detritivores and Decomposers.
Answer:
Differences between detritivores and decomposers are as follows

Detritivores	Decomposers
These are animals which feed on detritus.	These are microorganisms which obtain nourishment from organic remains.
These ingest the organic matter.	These decompose the organic matter by secreting digestive enzymes over it.
Ecologically, they cause pulverisation or fragmentation of detritus, e.g. earthworm, carrion beetle.	Ecologically, they cause humification and mineralisation of organic matter, e.g. Pseudomonas, slime moulds.

Question 4.
Production and Decomposition.
Answer:
Differences between production and decomposition are as follows

Production	Decomposition
It is the process of synthesis organic compounds/biomass from inorganic matter using sunlight by producers (e.g. plants).	It is the process of of breaking down of a substance/waste biomass into its constituent parts by decomposers, e.g. bacteria, fungi.
It traps the energy.	It releases the energy.
It builds up biomass from inorganic nutrients.	It releases inorganic nutrients from the biomass.