The resemblance in bone structure found in the forelimbs of various vertebrates exemplifies which of the following?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Homology
The forelimbs of whales, bats, cheetahs and humans are used for swimming, flying, running and grasping. Yet the same set of bones is found in all of them. Organs that share a basic structure because they come from a common ancestor, even though they now do different jobs, are called homologous organs.
Option (1) Convergent evolution — Incorrect. Convergent evolution gives different structures that come to do the same job, such as the wings of a butterfly and of a bird. The forelimbs show the reverse case: one structure doing different jobs.
Option (2) Analogy — Incorrect. Analogous organs look alike and do the same job but are not anatomically similar, like the eye of the octopus and of mammals. The forelimb bones are anatomically the same, so they are not analogous.
Option (3) Homology — Correct. The same bone pattern in forelimbs that do different jobs means the same structure developed along different directions to meet different needs. This is divergent evolution, and such organs are homologous. Homology points to common ancestry.
Option (4) Adaptive radiation — Incorrect. Adaptive radiation is the evolution of many different forms from one ancestral stock within one geographical area, such as Darwin’s finches or the Australian marsupials. It is about one stock spreading into many habitats, not about bone pattern in forelimbs.
NCERT Extract:
What are the Evidences for Evolution? – “… For example whales, bats, Cheetah and human (all mammals) share similarities in the pattern of bones of forelimbs (Figure 6.3b). 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. Homology indicates common ancestry.”