15. Endotherm

Endotherms, or warm-blooded animals, are capable of generating their own body heat independently from external temperatures. Endotherms can adjust their metabolic heat production in order to regulate their internal temperature; they have a greater number of mitochondria in their cells than ectotherms, which increases the amount of fats and sugars they can metabolize. The classification of endotherms consists of mammals and birds. The cat seen above, a mammal, is an example of an endotherm.