Biological

With regards to any given life system parameter, an organism may be a conformer or a regulator. On one hand, Regulators try to maintain the parameter at a constant level over possibly wide ambient environmental variations. While on the other hand, conformers allow the environment to determine the parameter. For instance, endothermic animals maintain a constant body temperature, while exothermic (both ectotherm and poikilotherm) animals exhibit wide body temperature variation. Examples of endothermic animals include mammals and birds, examples of exothermic animals include reptiles and some sea animals. Humans beings are nature's ultimate example of "regulators" because they control their paramater's in a variety of climates and conditions.

Behavioral adaptations allow exothermic animals to exert some control over a given parameter. For instance, reptiles often rest on sun-heated rocks in the morning to raise their body temperature. Regulators are also responsive to external circumstances, however: if the same sun-baked boulder happens to host a ground squirrel, the animal's metabolism will adjust to the lesser need for internal heat production.

Thermal image of a cold-blooded tarantula (cold-blooded or exothermic) on a warm-blooded human hand (endothermic).

An advantage of homeostatic regulation is that it allows an organism to function effectively in a broad range of environmental conditions. For example, ectotherms tend to become sluggish at low temperatures, whereas a co-located endotherm may be fully active. That thermal stability comes at a price since an automatic regulation system requires additional energy. One reason snakes may eat only once a week is that they use much less energy to maintain homeostasis.