Consider the following statements Assertion A The energy pyramid of an ecosystem is always upr...........

Environment and Ecology Concept of Ecosystems

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Consider the following statements.

Assertion (A): The energy pyramid of an ecosystem is always upright and narrows to the top.

Reason (R): The biomass in the upper trophic levels is generally very high as compared to the lower trophic levels.

In the context of the above, which of these is correct?

A is correct, and R is an appropriate explanation of A.

A is correct, but R is not an appropriate explanation of A.

A is correct, but R is incorrect.

Both A and R are incorrect.

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Explanation:

Justification: The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.
• When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction.
• An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.
• Since each higher trophic level receives only a fraction of energy of the lower trophic levels, the energy pyramid is narrow at the top. So, A is correct.
• But, generally (barring some aquatic ecosystems) lower trophic levels have higher biomass as compared to the higher trophic levels. So, R is incorrect. Moreover, even if this were to be so, it doesn’t explain A.