Define vestigial organs. Write names of some vestigial organs in human body and write the names of those animals in whom the same organs are functional.
Degenerated or underdeveloped useless organs of organisms are called as vestigial organs.
In living organisms, sudden development of new tissues or organs for living in the changing environment is not possible. Instead, existing organs undergo gradual changes.
A specific structure in the body is useful under certain situation. However, the same structure under different situation may become useless or even harmful.
Such structure begins to degenerate under such situation as per the principle of natural selection.
It takes hundreds of years for a structure to disappear.
Such organs are seen in different phases of disappearance in different animals.
An organ which is vestigial in one organism may not be vestigial in the other.
Appendix is a vestigial organ in humans but it is useful and fully functional organ in ruminants.
Muscles of ear pinna are vestigial in humans but useful in monkeys for movement of ear pinna.