Comparative anatomy

Comparative anatomy

Comparative anatomy is the study of similarities and differences in the anatomy of different organisms. It is closely related to evolutionary biology and phylogeny (the evolution of species). Comparative anatomy has long served as evidence for evolution, it indicates that various organisms share a common ancestor. Also, it assists scientists in classifying organisms based on similar characteristics of their anatomical structures. Comparative anatomy supports Darwin's theory of descent with modification, also known as evolution. A common example of comparative anatomy is the similar bone structures in forelimbs of cats, whales, bats, and humans. All of these appendages consist of the same basic parts; yet, they serve completely different functions. The skeletal parts which form a structure used for swimming, such as a fin, would not be ideal to form a wing, which is better-suited for flight. One explanation for the forelimbs' similar composition is descent with modification. Through random mutations and natural selection anatomical structures gradually became better-adapted to the every organism's respective habitat.[1] Two major concepts of comparative anatomy are: Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent. They may or may not perform the same function. An example is the forelimb structure shared by cats and whales. Analogous structures - structures similar in different organisms because they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of por oises 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. The rules for development of special characteristics which differ significantly from general homology were listed by Karl Ernst von Baer (the Baer laws). Born in 1517 Pierre Belon was a French naturalist who did research and held discussions on dolphin embryos as well as the comparisons between the skeletons of birds to the skeletons of humans. His research led to what is referred to as modern comparative anatomy. An engraving of Andreas Vesalius Around the same time, Andreas Vesalius was also making some strides of his own. A young anatomist of Flemish descent made famous by a penchant for amazing charts, he was systematically investigating and correcting the anatomical knowledge of the Greek physician Galen. He noticed that many of Galen's observations were not even based on actual humans. Instead, they were based on animals such as oxen.Up until that point, Galen and his teachings had been the authority on human anatomy. The irony is that Galen himself had emphasized the fact that you should make your own observations instead of using those of another. But this advice was lost during the numerous translations of his work. As Vesalius began to uncover these mistakes, other physicians of the time began to trust their own observations more than Galen. An interesting observation made by some of these physicians was the presence of homologous structures in a wide variety of animals which included humans. These observations were later used by Darwin as he formed his theory of Natural Selection.