The body temperature of ectotherms is determined solely by the environment. Many ectotherms select areas that have more favorable temperatures. Ectotherms rely primarily on physical mechanisms of energy (heat) exchange with the environment.
Another way of classifying animals is according to their Structural Strategies for thermoregulation. Animals can be divided into two groups: homeothermic and poikilothermic animals. Homeotherms are endothermic animals that maintain a very consistent body temperature within a very narrow temperature range. Birds and mammals are usually very strict homeotherms. Homeotherms can function quite efficiently in both hot and cold environments. Poikilotherms are animals that have not developed mechanisms for regulating the temperature of their internal environment. Therefore, their internal temperature changes with the temperature changes in the external environment. When poikilotherms are exposed to a cold environment, their internal temperature also falls. This makes the enzymes less efficient, so the animals become less active. Lizards and snakes are examples of poikilotherms. .
Other strategies of animals for thermoregulation are: (1) Physiological mechanisms such as the whirring of the wings of the dragonfly, as well as the dragonflies' alternating of flight and gliding. (2) Evaporative cooling is one method of thermoregulation in homeotherms. An example of this is sweating, which is a corrective response that aims to reduce the temperature of the organism. Another example of evaporative cooling is panting. (3) Hyperthermia is an acute condition resulting from excessive exposure to heat, it is also known as heat stroke. The homeothermal regulatory mechanisms become overwhelmed and are unable to effectively deal with the heat, and body temperature climbs uncontrollably. Signs include increasing body temperature, dehydration and lack of sweating, seizures, collapse and decreased consciousness which proceeds rapidly to multi-organ failure and death as the brain 'cooks'.
