General Anatomy or Comparative anatomy is the study of similarities and differences in the anatomy of different species. Two major concepts of comparative anatomy are:
• Homologous structures – These are the structures that are similar in different species because the species have common descent. They may or may not serve the same function. An example is the forelimb structure shared by cats and whales.
• Analogous structures – These are the structures similar in different organisms because they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually perform the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved from different ancestors, porpoises and sharks developed analogous structures as a result of their evolution in the same aquatic environment.