Humans are an endothermic species. This means that we produce our own body heat through the metabolic process. Mammals and birds are endothermic. Fish, reptiles, amphibians, and most invertebrates are ectothermic species. They get their body heat from an external means. The painted turtle is a good example of and ectothermic species. To be active the painted turtle must maintain its internal body temperature from about 65 to 75 degrees. So in the morning the turtle will need to sun for several hours after spending the night in the cold water. Once it warms up enough it can go out and forage for food, however it will have to return to basking frequently through out the day.