Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Predators help in maintaining species diversity in a community.
Reason (R): Predators act as ‘conduits’ for energy transfer across trophic levels.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are true but (R) is not the correct explanation of (A).
Predators do more than one job in a community, and the question asks which job explains species diversity.
Assertion (A): Predators help in maintaining species diversity in a community. — True. A is about the number of prey species a community can hold. When the starfish Pisaster was removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year.
Reason (R): Predators act as ‘conduits’ for energy transfer across trophic levels. — True. R is about energy flow: by eating prey, predators pass energy to the next trophic level.
Why R does not explain A? Energy transfer explains where the energy goes, not why more prey species survive. Diversity is kept because predators reduce the intensity of competition among competing prey species, so no single prey species can push the others out. Without the starfish, the invertebrates went extinct because of interspecific competition, not because energy stopped flowing. So both statements are true, but R is not the correct explanation of A.
NCERT Extract:
Population Interactions – “… Besides acting as ‘conduits’ for energy transfer across trophic levels, predators play other important roles. They keep prey populations under control.”
Population Interactions – “… Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species. In the rocky intertidal communities of the American Pacific Coast the starfish Pisaster is an important predator. In a field experiment, when all the starfish were removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year, because of interspecific competition.”