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."

History

Originally, as narrated in a recent history of the field, physiology focused primarily on human beings, in large part from a desire to improve

medical Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

practices. When physiologists first began comparing different

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

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.

Methodology

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. :This amounts to cataloging functional aspects of biological diversity, and has recently been criticized as "stamp collecting" with the suggestion that the field should move beyond that initial, exploratory phase. 2. The use of physiological information to reconstruct

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationships of organisms.
:In principle physiological information could be used just as morphological information or DNA sequence is used to measure evolutionary divergence of organisms. In practice, this has rarely been done, for at least four reasons: :* physiology doesn't leave many

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

cues, :* it can't be measured on

museum A museum is an institution dedicated to displaying or Preservation (library and archive), preserving culturally or scientifically significant objects. Many museums have exhibitions of these objects on public display, and some have private colle ...

specimens, :* it is difficult to quantify as compared with morphology or DNA sequences, and :* physiology is more likely to be adaptive than DNA, and so subject to parallel and

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

, which confuses phylogenetic reconstruction. 3. To elucidate how physiology mediates interactions between organisms and their environments. :This is essentially physiological ecology or ecological physiology. 4. To identify "model systems" for studying particular physiological functions. :Examples of this include using squid giant axons to understand general principles of nerve transmission, using rattlesnake tail shaker muscles for measurement of in vivo changes in metabolites (because the whole animal can be put in an NMR machine), and the use of ectothermic poikilotherms to study effects of temperature on physiology. 5. To use the "kind of animal" as an experimental variable. : "While other branches of physiology use such variables as light, temperature, oxygen tension, and hormone balance, comparative physiology uses, in addition, species or animal type as a variable for each function."Prosser (1950, p. 1) : 25 years later, Prosser put things this way: "I like to think of it as that method in physiology which uses kind of organism as one 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. Similarly, comparative physiologists have been attracted to "unusual" organisms, such as very large or small ones. As an example, of the latter, hummingbirds have been studied. As another example, giraffe have been studied because of their long necks and the expectation that this would lead to specializations related to the regulation of

blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...

. More generally, ectothermic

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

have been studied to determine how

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

acid-base balance and pH change as

body temperature Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

changes.

Funding

In the United States, research in comparative physiology is funded by both the

National Institutes of Health The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Service ...

and the

National Science Foundation The U.S. National Science Foundation (NSF) is an Independent agencies of the United States government#Examples of independent agencies, independent agency of the Federal government of the United States, United States federal government that su ...

Societies

A number of scientific societies feature sections on comparative physiology, including:
American Physiological Society

Australian & New Zealand Society for Comparative Physiology & Biochemistry

Canadian Society of Zoologists

Society for Integrative and Comparative Biology
*

Society for Experimental Biology The Society for Experimental Biology is a learned society for animal, cell and plant biologists. It was founded in 1923 at Birkbeck College to "promote the art and science of experimental biology in all its branches". It aims to demonstrate the im ...

Biographies

Knut Schmidt-Nielsen Knut Schmidt-Nielsen (September 24, 1915 – January 25, 2007) was a comparative physiologist and Professor of Physiology Emeritus at Duke University. Background Born in Trondheim, Norway. He was educated in Oslo and Copenhagen. He became a stud ...

(1915–2007) was a major figure in vertebrate comparative physiology, serving on the faculty at

Duke University Duke University is a Private university, private research university in Durham, North Carolina, United States. Founded by Methodists and Quakers in the present-day city of Trinity, North Carolina, Trinity in 1838, the school moved to Durham in 1 ...

for many years and training a large number of student
(obituary)
He also authored several books, including an influential text, all known for their accessible writing style. Grover C. Stephens (1925–2003) was a well-known invertebrate comparative physiologist, serving on the faculty of the

University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...

until becoming the founding chairman of the Department of Organismic Biology at the University of California at Irvine in 1964. He was the mentor for numerous graduate students, many of whom have gone on to further build the fiel
(obituary)
He authored several books and in addition to being an accomplished biologist was also an accomplished pianist and philosopher.

Some journals that publish articles in comparative animal physiology

American Journal of Physiology - Regulatory, Integrative and Comparative Physiology

Annual Review of Physiology

Comparative Biochemistry and Physiology

Ecological and Evolutionary Physiology
(formerly Physiological and Biochemical Zoology)
Integrative and Comparative Biology

Journal of Comparative Physiology

Journal of Experimental Biology

History

Methodology

Funding

Societies

Biographies

Some journals that publish articles in comparative animal physiology

See also

References

Further reading