Comparative anatomy is the study of the anatomy of an organ in various groups of vertebrates, to derive evolutionary importance from it, and to know why an organ evolved the way it is present today. The evolution of an organ is influenced by both genetic factors and environmental conditions, with natural selection determining whether the organ is retained or lost over time.
The subject of the relationship between form (anatomy) and function caught the attention of comparative anatomists at the end of the eighteenth century. This subject involves the concepts of homology and analogy, which are comprehensible only in the context of the principle of evolution.