UNIT 3: Homeostasis

Question 1

homeostasis

Answer 1

the maintenance of a constant internal environment

Question 2

temperature regulation in plants

Answer 2

if a plant is too hot then it will increase transpiration in an effort to cool down

Question 3

temperature regulation in animals

Answer 3

1. endotherms - animals whose internal temperature remains constant despite environmental temperature changes e.g. mammals and birds
2. ectotherms - animals whose internal temperature changes with environmental temperature e.g. insects, amphibians, fish

Question 4

mechanisms to enable endotherms to maintain body temp (cold)

Answer 4

1. shivering - rapid contraction and relaxation of skeletal muscles helps to generate heat.
2. vasoconstriction- narrowing of the cappilaries near the surface of the body directs blood to core areas helping to conserve heat.
3. piloerection - piloerctor muscles contract causing hair to stand up away from the skin, trapping a layer of air close to the skin.
4. thyroxine secretion - thyroxine being a hormone that increases metabolism thereby generating heat

Question 5

mechanisms to enable endotherms to maintain body temp (hot)

Answer 5

1. sweating - release of sweat onto the surface of the skin via sweat glands cools the body down through evaporation.
2. vasodilation - widening of the capillaries close to the surface of the body thereby releasing heat and cooling the body down.
3. rapid breathing - exchanges more air with the lungs helping to release heat from the body

Question 6

ph regulation

Answer 6

pH levels must be tightly regulated in all living organisms. this enables enzymes to function properly.
in animals blood pH must be kept at 7.4. the acidity of the blood is controlled by the lungs and kidneys of animals.
plants rely on the soil being the correct pH to enable full growth and reproduction

Question 7

glucose level regulation

Answer 7

glucose levels in animals must be maintained at a concentration of approx. 1 g/L. if it drops too low, coma and death can result. if glucose levels rise too high it can cause damage to blood vessels and nerves. controlled by insulin (lowers blood glucose) and glucagon (rises blood glucose)

Question 8

osmoregulation

Answer 8

the maintenance of the correct amount of water in the body. The kidneys will excrete excess water and conserve water if the body is lacking water. In plants the stomata of the leaves will close if there is not enough water in the plant

Question 9

calcium level regulation

Answer 9

calcium is needed in animals for healthy bones and teeth and also muscle contraction.
if calcium levels are low, the parathyroid glands in the neck secrete parathormone.