Ectotherm vs. Endotherm

Ectothermnoun

(biology) An animal, such as an amphibian, fish, reptile, or arthropod, which has a limited ability to regulate its body temperature and whose body temperature thus depends on the ambient temperature.

Ectothermnoun

an animal whose body temperature varies with the temperature of its surroundings; any animal except birds and mammals

Ectotherm

An ectotherm (from the Greek ἐκτός (ektós) and θερμός (thermós) ) is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Such organisms (for example frogs) rely on environmental heat sources, which permit them to operate at very economical metabolic rates.Some of these animals live in environments where temperatures are practically constant, as is typical of regions of the abyssal ocean and hence can be regarded as homeothermic ectotherms.

Endothermnoun

(biology) an animal that maintains a constant body temperature

Endotherm

An endotherm (from Greek ἔνδον endon and θέρμη thermē ) is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production.