Question

Assertion (A): The flow of energy in the ecosystem is said to be cyclic because the sun’s energy radiated from the living organisms of a food chain can be reused by plants in photosynthesis.

Reason (R): When we move from the first trophic level of producers (plants) to second trophic level of herbivores and third trophic level of carnivores, the amount of energy available gradually decreases.

Options

• Both A and R are true and R is correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Answer 1

A is false but R is true.

Explanation:

The flow of energy in an ecosystem is not cyclic; it is unidirectional. Energy flows from the Sun → producers → consumers → decomposers, and a large part of it is lost as heat at each trophic level. It cannot be reused by plants in photosynthesis. Therefore, Assertion (A) is false.

When energy is transferred from producers (first trophic level) to herbivores (second trophic level) and then to carnivores (third trophic level), the amount of available energy gradually decreases, as only about 10% is transferred to the next trophic level. Therefore, Reason (R) is true.

Hence, the correct answer is (d) A is false but R is true.