The main sources for this heat are the sun and the air around the body. Ectotherms lie in the sun to warm their bodies up so that they can work properly.
Modern ectotherms include crocodiles, alligators and lizards.
Ectotherms are also poikilotherms. This means that their body temperature varies widely.
So, a cold-blooded animal, as refered to on these pages, is actually a poikilothermic ectotherm.
