Ectotherm, any so-called cold-blooded animal—that is, any animal whose regulation of body temperature depends on external sources, such as sunlight or a heated rock surface. The ectotherms include the fishes, amphibians, reptiles, and invertebrates.

Why are ectotherms not cold-blooded?

Cold-blooded animals, such as reptiles, amphibians, insects, arachnids and fish, were not. ... Ectotherms are animals that don't have the ability to retain the heat generated by their metabolism. When it's cold outside, the metabolism of ectotherms slows down, as does their ability to move.

Are endotherms warm blooded?

Endotherm, so-called warm-blooded animals; that is, those that maintain a constant body temperature independent of the environment. The endotherms primarily include the birds and mammals; however, some fish are also endothermic.