As a result of __________, the same structure takes different forms because it performs different functions:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Convergent evolution
Note: The given answer is as per the official NTA Answer Key. However, the correct answer is Option (1) Divergent evolution, because NCERT says that the same structure developing in different directions for different needs is divergent evolution, as explained below.
Organs of different animals may share the same basic structure, like the forelimbs of whales, bats, cheetahs and humans. They come from a common ancestor, but they now do different jobs. The same structure has developed in different directions to meet different needs. This is divergent evolution, and such organs are homologous. The opposite case, different structures evolving for the same function, is convergent evolution.
(1) Divergent evolution — Correct as per NCERT. One structure takes different forms because it does different functions.
(2) Convergent evolution — The answer given by NTA, but it does not fit the sentence. In convergent evolution different structures evolve for the same function, like the wings of a butterfly and a bird. These are analogous organs.
(3) Co-existence — Incorrect. Co-existence only means living together in the same place. It says nothing about how a structure changes.
(4) Co-evolution — Incorrect. Co-evolution is the linked evolution of two interacting species, such as a flower and its pollinator. It does not describe one structure taking different forms.
NCERT Extract:
What Are the Evidences for Evolution? – “… Though these forelimbs perform different functions in these animals, they have similar anatomical structure – all of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs. Hence, in these animals, the same structure developed along different directions due to adaptations to different needs. This is divergent evolution and these structures are homologous.”