i. The organs or parts that are similar in basic structural plan of development but different in functions are called homologous organs.
ii. A study of hand of man, fins of whale, wings of bird, forelimb of horse suggest that all these organs of the animals belonging to different groups show similar internal organization, i.e. presence of humerus, radio-ulna, carpals, metacarpals and phalanges.
iii. However, the external appearance of hand of man, fins of whale, wing of bird, forelimb of horse is different.
iv. Not only that, these organs perform different functions, hand of man for gripping, wings of bird for flying, forelimb of horse for running, fins of whale for swimming.
v. The study of homologous organs suggest that these animals belonging to different groups have descended from a common ancestor. In other words, they have evolved from a common ancestor.
