1.1.3 Maintaining body temperature - ectotherms

Question 1

What is an Ectotherm?

Answer 1

An ectotherm is an organism that relies on external sources of heat to regulate its body temperature.

Question 2

Why can’t ectotherms regulate their own body temperatures?

Answer 2

They cannot increase respiration rates to generate heat internally. (However once active moving muscles will generate heat due to increased respiration).

Question 3

What are two advantages of being an ectotherm?

Answer 3

1. Ecotherms use less of their food in respiration, therefore a greater proportion of energy gained from food can be used for growth.
2. They can survive for long periods of time without eating.

Question 4

What are two disadvanatges of being an ectotherm?

Answer 4

1. If the temperature is cooler they are less active, meaning a greater risk of predation.
2. They may not be capable of activity during winter as they never warm up sufficiently. This means they need to build up stores of energy to last them over the winter period.

Question 5

Give examples of behavioural responses used by ectotherms to regulate their body temperature explain how the responses achieves this?

Answer 5

1. Exposing body to the sun, enables more heat to be absorbed. (Snakes)
2. Hide in burrow, reduces heat absorption by keeping out of the sun. (Horned Lizards)
3. Orientate body to the sun, exposes a larger surface area for more heat absorption. (Locusts)
4. Orientate body away from the sun, exposes a lower surface area so that less heat is absorbed. (Locusts)

Question 6

Give examples of physiological responses used by ectotherms to regulate their body temperature explain how the responses achieves this?

Answer 6

1. Altering body shape (e.g. expanding or contracting rib cage), which exposes more or less surface area to the sun. (Horned Lizards)
2. Increase breathing movements. This will increase the evaportaion of water and aid cooling. (Locusts)

Question 7

S&C

Answer 7

The bees in the centre of the swarm will be the warmest, therefore by moving to the outer regions of the swarm they will cool down. The space they have created can be filled with bees from the outside of the swarm so they can heat up, this will help to maintain the temperature of the swarm. In hot weather bees will create more air passages and wider air passages to allow the air to carry the heat away. In cooler temperatures the passages will be fewer in number and narrower.