The main difference between Homeothermic and Poikilotherm is that the Homeothermic is a thermoregulation that maintains a stable internal body temperature regardless of external influence and Poikilotherm is a an organism whose internal temperature varies considerably.
Homeothermy or homothermy is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate environment (from Greek ὅμοιος homoios “similar” and θέρμη thermē “heat”). Homeothermy is one of the three types of thermo regulation in warm-blooded animal species. Homeothermy’s opposite is poikilothermy.
Homeotherms are not necessarily endothermic. Some homeotherms may maintain constant body temperatures through behavioral mechanisms alone, i.e., behavioral thermoregulation. Many reptiles use this strategy. For example, desert lizards are remarkable in that they maintain near-constant activity temperatures that are often within a degree or two of their lethal critical temperatures.
A poikilotherm () is an animal whose internal temperature varies considerably. It is the opposite of a homeotherm, an animal which maintains thermal homeostasis. While the term in principle can apply to all organisms, it is usually only applied to animals, and mostly to vertebrates. Usually the variation is a consequence of variation in the ambient environmental temperature. Many terrestrial ectotherms are poikilothermic. However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature (i.e. are homeothermic). It is this distinction that often makes the term “poikilotherm” more useful than the vernacular “cold-blooded”, which is sometimes used to refer to ectotherms more generally.
Poikilothermic animals include types of vertebrate animals, specifically fish, amphibians, and reptiles, as well as a large number of invertebrate animals. The naked mole-rat is the only mammal that is currently thought to be poikilothermic.
Capable of maintaining a relatively constant body temperature independent of the surrounding environment.
A cold-blooded animal