Endothermisiin

Endothermisiin is a Finnish term used to describe organisms that regulate their body temperature primarily through internal heat production rather than relying solely on external heat sources. In biology, such organisms are typically referred to as endotherms. Endothermy enables relatively stable core body temperatures over a broad range of environmental conditions, though the term does not imply uniform temperatures in all tissues. Endothermy is contrasted with ectothermy, in which body temperature is largely determined by the ambient environment.

Endotherms generate heat through metabolic processes, including respiration and nutrient oxidation. They regulate heat by a combination of physiological and behavioral strategies, such as shivering and non-shivering thermogenesis, activity of brown adipose tissue, and insulation from fur, feathers, or fat. Many endotherms maintain a relatively high basal metabolic rate and, in many species, a stable core temperature. They may also employ evaporative cooling mechanisms to prevent overheating in hot conditions.

Taxa and examples: The most widely recognized endotherms are mammals and birds. In addition, several fish groups—most notably lamnid sharks and some tunas—exhibit regional endothermy, keeping certain body parts warmer than the surrounding water. Evolutionarily, endothermy arose independently in the lineages leading to mammals and birds, involving complex changes in metabolism, circulation, and heat production. The energy costs of maintaining endothermy are high, contributing to higher food intake and enabling activity in colder or more variable climates and environments where ectothermy would be limiting.