Describe any three methods of tracing evolutionary relationship among arganisms.

(i) Homologous organs. Homologous organs are those organs which are formed on the same fundamental structural plan but they differ in their shapes because they have to function differently.
Example: Forelimbs of frog and bird.
(ii) Analogous organs. Analogous organs are structurally and developmentally quite different from each other i.e., they have different origins.
But they performs similar functions in different animals.
Example: The wings of a bird and wings of a bat.
(iii) Fossils. The remains or impressions of dead and decayed plants and animals are called fossils. Fossils tell us how new species are developed from the old one.
Example: Fossils of dinosaurs.