Thermoregulation In Ectotherms

Question 1

Define thermoregulation

Answer 1

The maintenance of a relatively constant core body temperature.

This ensure that enzyme activity isn’t affected. In humans the optimum temp for enzymes is 37°C

Question 2

What are ectotherms? E.g.

Answer 2

• can’t control their body temperature internally - they control their temperature by changing their behaviour
• their body temp is heavily dependent on their environment

E.g. invertebrate animals, fish, amphibians, reptiles

Ectotherms have a variable metabolic rate because they can’t keep their internal temperature constant.
This means the activity level of ectotherms depends on the external temperature too - they’re more active at higher temperatures.

Question 3

Describe behavioural responses ectotherms have in order to warm up

Answer 3

• they may bask in the Sun, orientate their bodies so that the maximum surface area is exposed to the Sun.
  E.g. lizards often bask for long periods of time to get warm enough to move fast and hunt for prey
• ectotherms can increase their body temperature through conduction by pressing their bodies against the warm ground
• iguanas contract their muscles and vibrate generating metabolic heat

Question 4

Behavioural responses ectotherms have in order to cool down

Answer 4

• ectotherms may need to cool down, to prevent enzymes denaturing
  Ectotherms may shelter from the sun by seeking shade, hiding in the cracks in rocks, or even digging burrows
• To cool down they press their bodies against cool, shady earth or stones, or move to water
  -minimise movements to reduce metabolic heat
• they orientate their bodies so that the minimum surface area is exposed to the Sun

Question 5

Describe ecotherms’ physiological responses to warming

Answer 5

Even though much of thermoregulation by ectotherms is the result of behavioural response, some have physiological responses

Dark colours absorb more radiation than light colours
- lizards in colder climates tend to be darker than lizards in hotter countries, so that they get warmer by absorbing more radiation from the Sun

Question 6

Difference in thermoregulation between endothermic and ectotherms

Answer 6

• ectotherms are more vulnerable to changes in the environment than endotherms
  But through behavioural and psychological responses ectotherms are able to keep a relatively stable core temp
• ectotherms need less food than endotherms as they use less energy regulating their internal temperatures, so they can survive in habitats where food is in short supply