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Chapter 29: Homeostasis Leaving Certificate Biology Higher Level Homeostasis • Homeostasis is the maintenance of a constant internal environment – Factors that need to be controlled: • • • • • Temperature pH Glucose levels Water and salt levels (osmoregulation) Calcium levels Temperature regulation • Plants can survive in a range of temperatures. If it is too hot then transpiration increases. Also, heat shock proteins are produced to protect enzymes from excess heat. • Animals can also resists quite large changes in temperature. There are two ways in which animals regulate internal temperature: – Ectotherm – animals whose internal temperature varies with their environment. – Endotherm – animals whose internal temperature does not change with external temperature. pH regulation • Enzymes are affected by changes in pH. Therefore, all living organism have to control their pH very carefully. • In plants the pH of the soil determines whether or not the plant will grow. • In animals pH can be controlled by the kidneys and by the respiratory system. Glucose regulation • Glucose levels, particularly in animals, must be maintained at certain levels. Too low and the animal will die; too high and the animal will develop diabetes. • Glucose levels in animals are generally controlled by the pancreas and the hormone insulin Osmoregulation • Osmoregulation is the maintenance of the correct amount of water in the living organism. • In plants, osmoregulation is carried out by the roots and by the process of transpiration. • In animals, the amount of water in the body is controlled by the kidneys and lungs and too a lesser extent, the skin Calcium regulation • Calcium is a very important mineral for all living organisms. • In plants it is used to make the middle lamella that holds plant cell walls together. • In animals it is used as a major component of bone, but is also very important for the conduction of impulses to muscles. • Calcium levels in animals are controlled by the parathyroids, by secreting the hormone parathormone.