5.1 - Communication and homeostasis

Question 1

Advantages and disadvantages of being an ectotherm

Answer 1

Advantages

• Less food used in respiration
• need less food
• more energy used for growth

Disadvantages

• less active in cold
• winter months

Question 2

Advantages and disadvantages of being an endotherm

Answer 2

Advantages

• can maintain constant body temperature despite external conditions
• can be active in colder conditions

Disadvantages

• a large portion of energy intake is needed to maintain body temperature in cold
• more food required
• less energy from food used for growth

Question 3

Endotherms – when too hot

Answer 3

• peripheral thermoreceptors in skin stimulated by change in external temperature
• impulses sent to hypothalamus
• vasodilation of arterioles to increase heat loss
• by radiation / conduction
• decreased metabolic rate / respiration in liver
• to generate less heat
• sweating/panting - evaporation to remove heat from skin
• hair muscles cause hairs to lie flat - no insulating air trapped - heat can radiate more easily to
  the surroundings
• example of negative feedback
• behavioural responses - go to shade, larger s.a for heat loss, less active

Question 4

Endotherms – when too cold

Answer 4

• peripheral thermoreceptors in skin stimulated by change in external temperature
• impulses sent to hypothalamus
• vasoconstriction of arterioles to reduce heat loss
• by radiation / conduction
• increased , metabolic rate/ respiration in liver
• to generate heat
• release of adrenaline
• rapid contraction and relaxation of sketetal muscles to shiver to generate heat
• hair muscles cause hairs to cause hairs to stand up - trap a layer of insulating air to prevent
  heat loss by conduction
• example of negative feedback