Growth and Allocation

Abstract

Physiological ecology deals with the adjustments, that is, the adaptations that organisms make to the physical and biological environments in which they live. They include the modification of rates of metabolism; the differential use of ectothermy and endothermy; the ability to balance salt and water budgets in terrestrial and aquatic environments; the adjustment of gas exchange in hypoxic, hyperbaric, and hypobaric environments; and the evolution of photosynthesis relative to water availability and the gas composition of the atmosphere. Geographical distributions may be limited by cold in montane and polar environments, water presence or absence in terrestrial regions, and the abundance of oxygen and carbon dioxide in aquatic and terrestrial environments, as well as the presence and the absence of competitors and selective food types. Many aspects of physiological ecology are associated with the ability to maintain an acceptable internal physiological state, which ultimately must be paid for by the acquisition of resources from the environment and by adequate energy expenditures. If this cannot be accomplished while maintaining a standard physiological state, many species reduce energy expenditure, such as entering torpor, but often with consequences for their life history, as with a reduction in reproductive output.