The current distinction is between animals whose body temperature is regulated chiefly by internal metabolic processess and those whose 25 temperature is regulated by, and who get most of their heat from, the environment. The former are called endotherms, and the latter are called ectotherms. Most ectotherms do regulate their body temperature, and they do so mainly by locomoting to favorable sites or by changing their temperature by choosing favorable environments, but primarily they regulate their temperature by making a variety of internal adjustments.