Which one of the following describes correctly the homologous structures : -
A
Organs with anatomical similarities, but performing different functions
B
Organs with anatomical dissimilarities but performing same function
C
Organs that have no function now, but had an important function in ancestors
D
Organs appearing only in embryonic stage and disappearing later in the adult
The answer is A.
Solution
Homologous organs have the same basic structure and embryonic origin (anatomical similarity), but they may perform different functions in different animals. Example: the forelimbs of whale (flipper), bat (wing), cheetah (running) and human (grasping) all have the same set of bones (humerus, radius-ulna, carpals, metacarpals, phalanges). In plants, thorns of Bougainvillea and tendrils of Cucurbita are homologous. They show divergent evolution from a common ancestor. Organs that differ in structure but do the same function are analogous; organs without function now are vestigial. So homologous structures are organs with anatomical similarities but performing different functions.
ConceptHomology and divergent evolution
Evidences of Evolution: Homologous Organs in past papers
2 questions from this chapter have appeared across 2 exam years.
