Homologous organs – The study of homologous organs suggests that the organs having same structure, but performing different functions, have evolved from a common ancestor.
Example: Forelimbs of a frog, lizard, bird and man are homologous organs.
Analogous organs – They show adoption of organs for common use.
Example: Wings of butterfly and wings of bat are analogous organs.
Fossils – They provide the missing links between two species.
Example: Archeopteryx/fossils of some dinosaurs with feathers. Archeopteryx provides a connecting link between reptiles and birds (Avian).