What defines an endotherm in terms of heat regulation?

An endotherm is defined by its ability to generate its own body heat through metabolic processes. This characteristic allows endotherms, such as mammals and birds, to maintain a relatively stable internal body temperature regardless of external environmental conditions. This internal heat generation is accomplished via processes like cellular respiration, which produces heat as a byproduct of energy production.

In contrast, ectotherms rely primarily on external environmental temperatures to regulate their body heat. While adaptations like basking in the sun or seeking shade may influence their temperature, ectotherms do not have the same metabolic capacity for heat production as endotherms do. The ability of endotherms to maintain homeostasis through their own metabolic heat generation provides them with advantages in varying climates and during periods of activity.