Comparative physiology is a subdiscipline of

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

that studies and exploits the diversity of functional characteristics of various kinds of

organisms In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi; ...

. It is closely related to

evolutionary physiology Evolutionary physiology is the study of the biological evolution of physiological structures and processes; that is, the manner in which the functional characteristics of individuals in a population of organisms have responded to natural selectio ...

and

environmental physiology Ecophysiology (from Ancient Greek, Greek , ''oikos'', "house(hold)"; , ''physis'', "nature, origin"; and , ''-logy, -logia''), environmental physiology or physiological ecology is a biology, biological List of academic disciplines, discipline that ...

. 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,

focused primarily on human beings, in large part from a desire to improve

medical Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

practices. When physiologists first began comparing different

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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 A garland is a decorative braid, knot or wreath of flowers, leaves, or other material. Garlands can be worn on the head or around the neck, hung on an inanimate object, or laid in a place of cultural or religious importance. Etymology From the ...

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 (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

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 preserved ...

cues, :* it can't be measured on

museum A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...

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 com ...

, which confuses phylogenetic reconstruction. 3. To elucidate how physiology mediates interactions between organisms and their environments. :This is essentially

physiological ecology Ecophysiology (from Greek , ''oikos'', "house(hold)"; , ''physis'', "nature, origin"; and , ''-logia''), environmental physiology or physiological ecology is a biological discipline that studies the response of an organism's physiology to enviro ...

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 Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

(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 Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics aro ...

have been studied. As another example,

giraffe The giraffe is a large African hoofed mammal belonging to the genus ''Giraffa''. It is the tallest living terrestrial animal and the largest ruminant on Earth. Traditionally, giraffes were thought to be one species, ''Giraffa camelopardalis ...

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 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 "blood pressure" r ...

. More generally,

ectothermic An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life a ...

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

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 in the c ...

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, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...

and the

National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National I ...

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 i ...

Biographies

Knut Schmidt-Nielsen Knut Schmidt-Nielsen (September 24, 1915 – January 25, 2007) was a prominent figure in the field of comparative physiology and Professor of Physiology Emeritus at Duke University. Background Born in Trondheim, Norway. He was educated in Oslo and ...

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

Duke University Duke University is a private research university in Durham, North Carolina. Founded by Methodists and Quakers in the present-day city of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco and electric power industrialist James ...

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, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Tw ...

until becoming the founding chairman of the Department of Organismic Biology at the

University of California at Irvine The University of California, Irvine (UCI or UC Irvine) is a public land-grant research university in Irvine, California. One of the ten campuses of the University of California system, UCI offers 87 undergraduate degrees and 129 graduate and pr ...

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
* Integrative and Comparative Biology * Journal of Comparative Physiology
Journal of Experimental Biology

References

{{DEFAULTSORT:Comparative Physiology Physiology Comparisons