Class 12 Biology Ecosystem MCQs with Answers

Sainik School Agra Classes provides a comprehensive set of Multiple Choice Questions (MCQs) for Class 12 Biology, focusing on the intricate topic of ecosystems. The ecosystem, a fundamental unit of ecology, encompasses the interactions between living organisms and their environment.

Sainik School Agra Classes’ MCQs delve into key concepts such as biotic and abiotic factors, trophic levels, energy flow, and nutrient cycling within ecosystems. These MCQs are meticulously crafted to test students’ understanding and application of ecological principles, preparing them for academic examinations and beyond. With Sainik School Agra Classes’ structured approach, students gain proficiency in analyzing ecological relationships and recognizing the importance of biodiversity conservation, ensuring a solid foundation in biology.

Q1. In a pond ecosystem, the food chain starts with:.

1.Zooplanktons.

2.Small insects.

3.Phytoplanktons.

4.Small fishes.

Q2. Zooplanktons represent which trophic level in an aquatic ecosystem?

1. T₁ level.
2. T₂ level.
3. T₄ level.
4. T₃ level.

Q3. Climax community is in a state of:

1. Non-equilibrium.
2. Equilibrium.
3. Disorder.
4. Constant change.

Q4. Which of the following statements is correct for secondary succession?

1. It begins on a bare rock.
2. It occurs on a deforested area.
3. It follows primary succession.
4. It is similar to primary succession, but has arelatively fast pace.

Q5. Among the following, where do you think the process of decomposition would be the fastest?

1. Tropical rain forest.
2. Antarctic.
3. Dry arid region.
4. Alpine region.

Q6. The amount of energy flow in an ecosystem generally:

1. Decreases at each higher trophic level.
2. Increase at each higher trophic level.
3. Remains same at each trophic level.
4. Is different in different food chains.

Q7. Among the following bio-geo-chemical cycles which one does not have losses due to respiration?

1. Phosphorus.
2. Nitrogen.
3. Sulphur.
4. All of the above.

Q8. Which one of the following has the largest population in a food chain?

1. Producers.
2. Primary consumers.
3. Secondary consumers.
4. Decomposers.

Q9. The following represents the different trophic levels of a food chain. Which one has the highest level of DDT
deposition in its body?

1. Sea crab.
2. Sea gull.
3. Predatory fish.
4. Photoplankton.

Q10. Secondary producers are:

1. Herbivores.
2. Producers.
3. Carnivores.
4. None of the above.

Q11. The second trophic level in a lake is

1. Phytoplankton.
2. Zooplankton.
3. Benthos.
4. Fishes.

Q12. Which one of the following is not an ecological pyramid?

1. Pyramid of energy.
2. Pyramid of standing crop aing crop.
3. Pyramid of biomass.
4. Pyramid of number.

Q13. Which of the following represents the sedimentary type of nutrient cycle?

1. Nitrogen cycle.
2. Carbon cycle.
3. Phosphorus cycle.
4. Oxygen cycle.

Q14. The sequence of communities of primary succession in water is:

1. Phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses and trees.
2. Phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees.
3. Free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses and trees.
4. Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and
   trees.

Q15. Which of these statements is correct?

1. The base of the energy pyramid contains the largest trophic level.
2. About 10% of energy available in food is actually incorporated into any trophic level.
3. Humans are at the top of energy pyramids.
4. All of these.

Q16. Which one of the following is not a major component of the ecosystem?

1. Decomposition.
2. Stratification.
3. Energy flow.
4. Nutrient cycling.

Q17. The process of mineralisation by micro organisms helps in the release of:

1. Inorganic nutrients from humus.
2. Both organic and inorganic nutrients from detritus.
3. Organic nutrients from humus.
4. Inorganic nutrients from detritus and formation of humus.

Q18. How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?

1. 1%.
2. 10%.
3. 40%.
4. 90%.

Q19. During the process of ecological succession the changes that take place in communities are:

1. Orderly and sequential.
2. Random.
3. Very quick.
4. Not influenced by the physical environment.

Q20. Pyramid of numbers is:

1. Always upright.
2. Always inverted.
3. Ether upright or inverted.
4. Neither upright nor inverted.