ABSTRACT
A clearer classification of the relationships between organisms and environmental temperature is to subdivide organisms into ectotherms and endotherms. Endotherms regulate their body temperature by producing heat within their own bodies; ectotherms rely on an external heat source. All organisms either gain or lose heat to their environment as well as producing heat through metabolic processes. There are three main temperature ranges of interest: very low, very high and the temperatures in between. The most dangerous thing about high temperatures is that they lie only a few degrees above the animal’s metabolic optimum, a result of the physio-chemical properties of their enzymes. In ectotherms, the metabolic rate is relatively slow at low temperatures and more rapid as the environment becomes warmer. Temperature may also act as a stimulus, determining whether the organisms will begin development. Variations in temperature may also be intimately associated with another environmental condition or resource such that the two are inseparable.
