Comparative anatomy is the study of similarities and differences in theanatomy of differentspecies. It is closely related toevolutionary biology andphylogeny[1] (theevolution of species).
The science began in theclassical era, continuing in theearly modern period with work byPierre Belon who noted the similarities of the skeletons of birds and humans.
Comparative anatomy has providedevidence of common descent, and has assisted in the classification of animals.[2]
The first specifically anatomical investigation separate from a surgical or medical procedure is associated byAlcmaeon of Croton.[3]Leonardo da Vinci made notes for a planned anatomical treatise in which he intended to compare the hands of various animals including bears.[4]Pierre Belon, a French naturalist born in 1517, conducted research and held discussions ondolphin embryos as well as the comparisons between the skeletons of birds to the skeletons of humans. His research led to modern comparative anatomy.[5]
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 other animals such as non-humanapes,monkeys, andoxen.[6] In fact, he entreated his students to do the following, in substitution for human skeletons, as cited by Edward Tyson : "If you can't happen to see any of these, dissect an Ape, carefully view each Bone, &c. ..." Then he advises what sort of Apes to make the choice of, as most resembling a Man : And conclude "One ought to know the Structure of all the Bones either in a Humane Body or in an Apes ; 'tis best in both ; and then to go to the Anatomy of the Muscles."[7] 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 one should make one's own observations instead of using those of another, but this advice was lost during the numerous translations of his work. AsVesalius began to uncover these mistakes, other physicians of the time began to trust their own observations more than those of Galen. An interesting observation made by some of these physicians was the presence of homologous structures in a wide variety of animals, even including humans. These observations were later used byDarwin as he formed his theory ofNatural Selection.[8]
Edward Tyson is regarded as the founder of modern comparative anatomy. He is credited with determining thatwhales anddolphins are, in fact, mammals. Also, he concluded thatchimpanzees are more similar to humans than tomonkeys because of their arms.Marco Aurelio Severino also compared various animals, including birds, in hisZootomia democritaea, one of the first works of comparative anatomy. In the 18th and 19th century, great anatomists likeGeorge Cuvier,Richard Owen andThomas Henry Huxley revolutionized our understanding of the basic build andsystematics ofvertebrates, laying the foundation forCharles Darwin's work onevolution. An example of a 20th-century comparative anatomist isVictor Negus, who worked on the structure and evolution of the larynx. Until the advent of genetic techniques likeDNA sequencing, comparative anatomy together withembryology were the primary tools for understandingphylogeny, as exemplified by the work ofAlfred Romer.[citation needed]
Two major concepts of comparative anatomy are:
Comparative anatomy has long served asevidence for evolution, now joined in that role bycomparative genomics;[10] it indicates that organisms share a common ancestor.
It also assists scientists in classifying organisms based on similar characteristics of their anatomical structures. 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 for forming 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, each organism's anatomical structures gradually adapted to suit their respective habitats.[11] The rules for development ofspecial characteristics which differ significantly from generalhomology were listed byKarl Ernst von Baer asthe laws now named after him.
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| Bacteria and fungi | ||
| Protists | ||
| Plants | ||
| Invertebrates | ||
| Mammals | ||
| Other vertebrates | ||
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