The rate of heating and cooling in poikilotherms decreases as body size increases. Most acquatic poikilotherms generally encounter temperature fluctuations of lesser magnitude and usually have poorly developed thermoregulatory capabilities than terrestrial forms. Adaptations to low temperatures Homeotherms Birds and mammals escape the thermal constraints of the environment by being endothermic at significant energy costs. High body temperatures may have evolved from an inability of large animals to dissipate rapidly the heat produced during periods of high activity. Among both poikilotherms and homeotherms are species that sometimes regulate their body temperature and sometimes do not.
Temperature is critical to the flight of insects.
To escape extreme temperatures, a few homeotherms become heterrothermic, allowing their core body temperatures to fall to near ambient temperature. Daily torpor of hummingbirds, bats, pocket mice. Hibernation of woodchuck, chipmunk, black bear. The optimal temperature range for completing a species life cycle, especially reproduction, imposes the greatest restriction on its distribution. Temperature is a major influence on the natural distribution of plants on continental, regional, and local scale.