As in other mammals, thermoregulation in humans is an important aspect of homeostasis. In thermoregulation, body heat is generated mostly in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles.
Changes in groups of organisms over time produce variations in a population. This relates to both macroevolution and microevolution. These are evolutions within a small group or a population and across the whole species.
