Question: where does heat in the body come from

title: Thermoregulation
text: Thermoregulation in organisms runs along a spectrum from endothermy to ectothermy . Endotherms create most of their heat via metabolic processes , and are colloquially referred to as warm - blooded . When the surrounding temperatures are cold , endotherms increase metabolic heat production to keep their body temperature constant , thus making the internal body temperature of an endotherm more or less independent of the temperature of the environment . One metabolic activity , in terms of generating heat , that endotherms are able to do is that they possess a larger number of mitochondria per cell than ectotherms , enabling them to generate more heat by increasing the rate at which they metabolize fats and sugars . Ectotherms use external sources of temperature to regulate their body temperatures . They are colloquially referred to as cold - blooded despite the fact that body temperatures often stay within the same temperature ranges as warm - blooded animals . Ectotherms are the opposite of endotherms when it comes to regulating internal temperatures . In ectotherms , the internal physiological sources of heat are of negligible importance ; the biggest factor that enables them to maintain adequate body temperatures is due to environmental influences . Living in areas that maintain a constant temperature throughout the year , like the tropics or the ocean , have enabled ectotherms to develop a wide range of behavioral mechanisms that enable them to respond to external temperatures , such as sun - bathing to increase body temperature , or seeking the cover of shade to lower body temperature . 

Answer: answer: Endotherms create most of their heat via metabolic processes , and are colloquially referred to as warm - blooded . Ectotherms use external sources of temperature to regulate their body temperatures . In ectotherms , the internal physiological sources of heat are of negligible importance. Living in areas that maintain a constant temperature throughout the year , like the tropics or the ocean , have enabled ectotherms to develop a wide range of behavioral mechanisms that enable them to respond to external temperatures , such as sun - bathing to increase body temperature , or seeking the cover of shade to lower body temperature .