Temperature relations of ectotherms

Question 1

Ectotherms

Answer 1

depend on heat from environment; most invertebrates, amphibians, reptiles and
fish

Question 2

Behavioural thermoregulation

Answer 2

Reptiles typically regulate their body temperature behaviourally, by moving to sun or shade
to absorb more or less heat

Question 3

Some can also change the rate at which heat is lost or gained by

Answer 3

regulating heart rate and the
flow of blood to the surface tissues

Question 4

For example, the Galapagos marine iguana

Answer 4

warms up rapidly while basking in the sun (rapid heart rate, blood diverted to surface) but slows the
rate of heat loss while diving by reducing heart rate and blood flow to surface.
[Note that endotherms may also use behavioural thermoregulation in addition to their other
mechanisms]

Question 5

Advantages and disadvantages of ectothermy relative to endothermy
Benefits:

Answer 5

By not expending energy to maintain a high body temperature, ectotherms can invest a
larger proportion of their energy budget in growth and reproduction;
Endotherms require less food, so spend less time foraging and so more time can be spent
hiding from predators.
Need less water (do not require water for evaporative cooling)