Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Plants have evolved an astonishing variety of morphological and chemical defences against herbivores.
Reason (R): Unlike animals, plants cannot run away from their predators.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are true and (R) is the correct explanation of (A).
For plants, herbivores are the predators. An animal can run, hide or fight back when a predator comes, but a plant is fixed in one place.
Assertion (A): Plants have evolved an astonishing variety of morphological and chemical defences against herbivores. — True. A is about what plants have: thorns as in Acacia and cactus, and chemicals that make the herbivore sick, stop its feeding or digestion, or even kill it.
Reason (R): Unlike animals, plants cannot run away from their predators. — True. R is about a limitation of plants: they cannot move away when an herbivore starts feeding on them.
Why R explains A? Since a plant cannot escape, the only way it can lessen the damage is to defend itself where it stands. This is why herbivory is a particularly severe problem for plants, and the book says plants “therefore” evolved their morphological and chemical defences. R gives the cause and A gives the result, so R is the correct explanation of A.
NCERT Extract:
Population Interactions – “… For plants, herbivores are the predators. Nearly 25 per cent of all insects are known to be phytophagous (feeding on plant sap and other parts of plants). The problem is particularly severe for plants because, unlike animals, they cannot run away from their predators. Plants therefore have evolved an astonishing variety of morphological and chemical defences against herbivores. Thorns (Acacia, Cactus) are the most common morphological means of defence.”