Some examples of homeostasis are the relatively constant levels of glucose and oxygen/carbon dioxide content of the blood.  Also, various mechanical  processes such as body temperature and blood pressure in mammals are homeostatically controlled. Homeostasis is most elaborately developed in birds and mammals, and in Biology 102 you will study various homeostatic mechanisms.  However, even at the cellular level, homeostasis is a critical feature of life.  For example, cells are able to regulate their chemistry.  Potassium ions are concentrated in cells while sodium ions are concentrated in fluids that surround the cell.  We'll revisit that idea in the unit on the cell.