Question

Short/Long answer type questions
How do data from comparative anatomy support the concept of common descent? Explain why vertebrate forelimbs are similar despite different functions.

Answer 1

Following are examples of comparative anatomy in support of common descent:-

(i) Among animals, studies on organ systems make it evident that structures in question show a common fundamental structural plan. Only minor changes in the structure have brought alterations in the morphology of organs.

Vertebrae in all higher vertebrates, for example, show the same fundamental structural plan. The vertebrae originate from similar embryonic rudiment. In less evolved vertebrates, vertebrae are simple but in highly evolved members, these are modified to a high degree but the basic structural plan remains unaltered.

(ii) The appendages of crustacea are built fundamentally on the same pattern and so they are considered to be serially homologous.

The forelimbs of all vertebrates are built upon the same pattern as they all have the same bones namely humerus, radius, ulna carpels. These bones differ in different animals because they are modified and specialized according to different modes of life, such as, swimming’ walking, jumping, flying, climbing, digging, etc. Such structures are said to be homologous organs.