Mammals and birds are described as endotherms because they
- A. always live in warm climates
- B. have a body temperature that follows the temperature of the surroundings
- C. generate most of their body heat from their own metabolism and hold it nearly constant
- D. are unable to lose heat through the skin
Explanation
An endotherm keeps its core temperature steady using heat from respiration, which lets enzymes work at their optimum whatever the weather and allows activity at night and in cold regions. The cost is a high food requirement, since much of that energy is spent simply on staying warm. An ectotherm such as a lizard depends on external heat and warms up by basking instead.