Question

Define and contrast the terms homologous and analogous structures.

Answer 1

Homologus Structures are the organs found in different types of species which are derived from a common ancestor or they have same developmental origin , their basic structure is same but they used differntly in different organism/species.

Example : Forelimbs of different vertebrates is a classic example of homologous structure. They have same developmental origin but the use of these limbs are different in different species (in human for grasping, in dog for walking etc).

Analogus Structures are the organs found in different types of species showing same function but they derived from different developmental origin.

Example : Fins of Fish and Flippers of Whale are the example of Analogous structure both these animals used it for swimming but evolutionary they are not related.

Homologus vs Analogous structure :

1. Homolgus structures have same developmental origin for all the species where as Analogous structure have different developmental origin in different species .

2. Homologous structure does not perform same function in different species but Analogous structure perform same function in different species.

3. The stages of development is same in holomologus structure but the stages of development is different in analogous structures.

4. Homologous structures shows adaptive radiation where as Analogous structure shows convergent evolution.