Poikilotherm is a cold-blooded animal; that is, an animal whose body temperature fluctuates with environmental temperature changes. An animal incapable of slef-regulation of body temperature. Fish, amphibians and reptiles are poikilotherms. Since these animals do not generate their own body temperature in the same way birds and mammals do, they depend entirely on an external source of heat; thus reptiles, such as snakes, crocodiles, and lizards need to bask in the sun for their body functions.

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