Question

how can we trace evolutionary relationships by the study of homologous organs

Answer 1

Homologous organs are defined as the structures that differ in appearance or perform different functions but have similar basic structure or developmental origin. For example: Wings of bats and forelimbs of lizards are homologous structures. They have same basic structure of bones, but perform different functions. Presence of homologous organs confirm divergent evolution, i.e., different organisms develop from a common ancestor. Presence of the same basic structure indicates that the organisms have common ancestral origin but evolved to perform different functions over the course of time. Therefore, homologous organs helps in establishing evolutionary relationship between organisms.