chapter 29: homeostasis leaving certificate biology higher level
TRANSCRIPT
Chapter 29: Homeostasis
Leaving Certificate BiologyHigher 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.