Homologous organs: Homologous organs are organs that have a similar basic structure but perform different functions. Example forelimbs of a human and whale.
Analogous organs: Analogous organs are organs that perform a similar function but are structurally different. Example wing of a bird and wing of a bat.
The presence of homologous and analogous organs helps in evolutionary studies and tracing the ancistory of a fossil. The presence of homologous organs suggests that the organims is closely related to that species and shares a common ancestory. By determining the homologous organs in fossils we can determine the possible ancestory of the present day organisms.
The presence of analogous organs in fossils helps us to understand that the two species live(d) in a common enviormental condition and have evolved to live in the same environment.
Thus by determining the presence of homologous and analogous organs in the fossils we can trace the possible ancestory of the present day organisms as well as determine the environmental conditions that prevailed in primitive times.