An ectotherm is an organism that relies on external heat sources to regulate body temperature. This means it uses very little energy to maintain homeostasis, but also has risks in case a heat source is not available. Ectotherms can survive on very little food, as a need to regulate body temperature is not present. An example of this is an alligator basking in the sun, which allows it to warm up, or looking for shade to cool down. Reptiles are ectothermic, including the Carolina anole lizard shown in this photograph.