Comparative anatomy

This article is about the study. For the experimental drum and bass band, see Comparative Anatomy (band).

Comparative anatomy is the study of similarities and differences in the anatomy of organisms. It is closely related to evolutionary biology and phylogeny (the evolution of species).

Description

Comparative anatomy is one of the strongest forms of evidence for evolution. It indicates that the organims shared a commom ancestor, it also helps scientists to classify the organisms based on their anatomical stuctures. Comparative anatomy also strongly supports Darwin's idea of descent with modification. A very popular example of comparative anatomy is the similarities between the make up of the forelimbs of cats, whales, bats, and humans. All of these appendages are made of the same bones but are used completely differently. Surely a structure used to fly would not be the ideal stucture for swimming would it? The only logical explanation would be that the forelimbs are so similiar because they developed from a common ancestor. Each basic structure was modified due to the different functions performed by each organism. Two major concepts of comparative anatomy are:

1. 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.
2. Analogous structures - structures which are 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 torpedo body shape of porpoises and sharks. It evolved in a water environment, but the animals have different ancestors.

The rules for development of special characteristics which differ significantly from general homology were listed by Karl Ernst von Baer (the Baer laws).

History

Edward Tyson is regarded as the founder of comparative anatomy. He is credited with determining that marine mammals are, in fact, mammals. Also, he concluded that chimpanzees are more similar to humans than to monkeys because of their arms. Marco Aurelio Severino also compared various animals, including birds, in his Zootomia democritaea, one of the first works of comparative anatomy. In the 18th and 19th century, great anatomists like George Cuvier, Richard Owen and Thomas Henry Huxley revolutionized our understanding of the basic build and systematics of vertebrates, laying the foundation for Charles Darwins work on evolution. Until the advent of genetic techniques like DNA sequencing, comparative anatomy together with embryology were the primary tools for understanding phylogeny, as exemplified by the work of Alfred Romer.

Today comparative anatomy is still taught and used, particularly in the field of paleontology.

See also

• Cladistics
• Phylogenetics