Comparative physiology

Comparative physiology is a subdiscipline of physiology that studies and exploits the diversity of functional characteristics of various kinds of organisms. It is closely related to evolutionary physiology and environmental physiology. Many universities offer undergraduate courses that cover comparative aspects of animal physiology. According to Clifford Ladd Prosser, "Comparative Physiology is not so much a defined discipline as a viewpoint, a philosophy."

Originally, physiology focused primarily on human beings, in large part from a desire to improve medical practices. When physiologists first began comparing different species it was sometimes out of simple curiosity to understand how organisms work but also stemmed from a desire to discover basic physiological principles. This use of specific organisms convenient to study specific questions is known as the Krogh Principle.

C. Ladd Prosser, a founder of modern comparative physiology, outlined a broad agenda for comparative physiology in his 1950 edited volume (see summary and discussion in Garland and Carter):

1. To describe how different kinds of animals meet their needs.

2. The use of physiological information to reconstruct phylogenetic relationships of organisms.

3. To elucidate how physiology mediates interactions between organisms and their environments.

4. To identify "model systems" for studying particular physiological functions.

5. To use the "kind of animal" as an experimental variable.

Comparative physiologists often study organisms that live in "extreme" environments (e.g., deserts) because they expect to find especially clear examples of evolutionary adaptation. One example is the study of water balance in desert-inhabiting mammals, which have been found to exhibit kidney specializations.

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