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Ecosystem Class 12 Biology MCQ With Solutions

Update on: 02 Feb 2024, 11:20 AM

Ecosystem Class 12 Biology MCQ with Answers has been organized according to the latest exam pattern in the CBSE Class 12 Biology syllabus for the upcoming CBSE Class 12 Biology Exam. Ecosystem cover topics like ecosystem – structures and functions, These questions are designed to help students understand the concept thoroughly. They are helpful for revision and for grasping the concepts effectively. These MCQ questions cover in-text book questions and important topics to help students assess their preparation level for CBSE board exams.

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CBSE Class 12 Chapter 12 Ecosystem MCQs

Check below the MCQ Questions for class 12 Biology with answers and Clear your idea of Chapter 12 Ecosystem.

Q.1. The ecological pyramids that can never be inverted in

(a) pyramids of dry biomass
(b) pyramids of energy
(c) pyramids of biomass
(d) pyramids of number.

Answer

(b): The pyramid of energy can never be inverted. It represents the amount of energy at each trophic level of the food chain. It is always upright because the energy flows from one trophic level to the next trophic level, some energy is always lost to the atmosphere

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Q.2. In an ecosystem energy enters through

(a) herbivores (b) carnivores
(c) producers (d) decomposers.

Answer

(c): The energy enters in an ecosystem through producers. Plants are producers which convert solar energy into chemical energy through photosynthesis. From producers, the energy is then transferred to the herbivores and carnivores. The animals eating plants are called as primary consumers or herbivores and animals eating primary consumers are called as secondary consumers or carnivores. Decomposers are those which decay the waste organic matter and release energy back in the environment.

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Q.3. Only 10% energy is transferred from a trophic level to the next trophic level was proposed by

(a) Lindeman (b) Tansley
(c) Stanley (d) Weismann

Answer

(a): The ten percent law of transfer of energy from one trophic level to the next was introduced by Raymond Lindeman. According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of energy from the organic matter is stored. The remaining is lost during the transfer, broken down in respiration, or lost to incomplete digestion by higher trophic level.

Q.4. Which of the following statements regarding energy flow are false?

I. The detritus food chain begins with dead organic matter.
II. In aquatic ecosystem, detritus food chain is the major conduit for energy flow.
III. In terrestrial ecosystem a larger fraction of energy flows through grazing food chain.
IV. Producers belong to the first trophic level of the food chain.

(a) II and III only (b) III and IV only
(c) I and II only (d) I, II and III only

Answer

(a): Food chain is the linear sequence of organisms where latter eats the former. There are two types of food chains: grazing food chain (GFC) and detritus food chain (DFC). GFC starts with green plants as producers and ends at secondary carnivores. The DFC begins with dead organic matter and is made up of decomposers which meet their energy and nutrient requirements by degrading dead organic matter or detritus. In an aquatic ecosystem, GFC is the major conduit for energy flow, while in a terrestrial ecosystem, a much larger fraction of energy flows through DFC than through the GFC.

Q.5. The average price tag on ecosystem services determined by Robert Constanza and his colleagues was

(a) 3 trillion USD (b) 13 trillion USD
(c) 23 trillion USD (d) 33 trillion USD.

Answer

(d): In 1997, Constanza and his colleagues estimated the annual net worth of the biosphere: US$33 trillion, a figure greater than the annual gross national products (GNP) of all the world’s economies combined. According to them, the soil formation accounts for about 50 per cent of the total ecosystem services and recreation and nutrient cycling accounts for less than 10 percent each of the total ecosystem services. Out of all ecosystem services, the cost of climate regulation and habitat for wildlife are about 6 per cent each.

Q.6. The direction of energy flow is

(a) producers → carnivores → herbivores → decomposers
(b) producers → herbivores → decomposers → omnivores
(c) producers → herbivores → carnivores → decomposers
(d) producers → carnivores → herbivores → decomposers.

Answer

(c): Energy flow starts with the producers as they fix the solar energy, then the herbivores which are fed upon producers. Further the herbivores are eaten by the carnivores and after death, decomposed by the decomposers.

Q.7. In a food chain the peacock eats a snake which is fed upon frog. The frog eats insect while insect eats green plant. The position of peacock in food chain is

(a) primary producer (b) secondary producer
(c) at the top of apex (d) tertiary consumer.

Answer

(c): In the food chain, the green plant is the primary producer that traps the energy from sun. The insect (grasshopper) is the primary consumers, because they directly consume the green plant. The frog is the secondary consumer, because it eats the grasshopper. The snake is tertiary consumer that eats the frog. The peacock is the top most carnivore, because it eats the snake, therefore it would occupy the top of the apex position.

Q.8. The amount of nutrients, such as carbon, nitrogen,phosphorus and calcium present in the soil at any given time, is referred as

(a) standing crop (b) climax
(c) climax community (d) standing state.

Answer

(d): The amount of nutrients, such as carbon, nitrogen, calcium, etc., present in soil at any given time is referred to as the standing state. It varies in different kinds of ecosystem and also on seasonal basis.

Q.9. In the equation, GPP – R = NPP, R represents

(a) respiration losses (b) radiant energy
(c) retardation factor (d) environment factor.

Answer

(a): Gross sprimary productivity (GPP) is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. GPP minus respiration losses (R) is the net primary productivity GPP – R = NPP. Therefore, GPP is always more than NPP.

Q.10. Which of the following statements is not correct ?

(a) Pyramid of numbers in a grassland ecosystem is upright.
(b) Pyramid of biomass in sea is generally inverted.
(c) Pyramid of biomass in sea is generally upright.
(d) Pyramid of energy is always upright.

Answer

(c): Pyramid of biomass in sea is generally inverted. In an aquatic system like sea, the producers are small organisms, their biomass is least and this value gradually shows an increase towards the apex of the pyramid, thus making the pyramid of biomass inverted in shape.

We hope the MCQs for the CBSE Class 12 Biology Chapter 12 on Ecosystem are helpful for your board exam preparation.

Keep learning and stay updated with us for more CBSE exam updates.

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