How is a bear's fur related to homeostasis?
Well it keeps the heat from escaping of course...
Fur in a bear contains lots of hair, which stand up when cold to trap hot air and keep it from escaping. When the bear is too hot, the hairs lie down to let it release all the hot air by radiation, and therefore cooling down the bear. This type of negative feedback loop ensures that the bear has a stable temperature inside its organs for maximum efficiency of chemical reactions happen inside it.