key concept 39.4 Body Temperature Depends on the Balance between Heat In and Heat Out of the Body

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Body temperature is a measure of the heat content of the body. Animals produce heat internally through their metabolism, and they continuously exchange heat with their environment. The balance between heat gain and heat loss determines the animal’s body temperature. Thermoregulatory adaptations enable animals to modulate the various paths of heat exchange between themselves and their environment.

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  • Endotherms can increase metabolic heat production to balance increased heat loss to the environment, whereas ectotherms rely largely on behavior to control their heat exchange with the environment.

  • The four avenues of heat exchange between an animal and its environment are radiation, convection, conduction, and evaporation.

  • A countercurrent heat exchange system in some highly active fishes conserves heat generated by muscle activity.