Evolutionary physiology
![Natural and sexual selection are often presumed to act most directly on behavior (e.g., what an animal chooses to do when confronted by a predator), which is expressed within limits set by whole-organism performance abilities (e.g., how fast it can run) that are determined by subordinate traits (e.g., muscle fiber-type composition). A weakness of this conceptual and operational model is the absence of an explicit recognition of the place of life history traits.](/Images/godic/202501/12/Phenotypic_Hierarchy_1.svg2049.png")
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Evolutionary physiology is the study of physiological evolution, which is to say, the manner in which the functional characteristics of individuals in a population of organisms have responded to selection across multiple generations during the history of the population.