Thermodynamic Equilibria of Animals with Environment

Abstract

All processes of life, all physiological events, do work and expend energy. A continuing supply of energy is necessary for an animal to live. One of the primary means by which the environment influences animals is through the exchange of energy. If the animal takes in more energy than it gives out it will get warmer, overheat and perish. If the animal loses more energy than it gains it will cool and not survive. An animal may warm or cool for a limited period of time, but on the average, over an extended period of time, an animal must be in energy balance with its environment: The mobility of most animals permits them to seek the environment most compatible with their physiological requirements for energy. The factors of the environment which are primarily re- sponsible for energy flow to an animal are several, e.g. radiation (sunlight, skylight, and radiant heat), air temperature, wind, and humidity. There are other environmental factors, such as the gravitational, elec- trical, or magnetic fields, which might determine en- ergy flow between animals and environment but may be ignored as generally not significant to the energy budget of an animal. The microclimate around an animal is thought of as a four dimensional space in which the four independent variables-radiation, wind, air temperature, and humidity-are acting si- multaneously and are each time dependent.