1.1.4 Maintaining body temperature - endotherms

Question 1

What is an endotherm?

Answer 1

An endotherm is an organism that can control production and loss of heat to maintain their body temperature.

Question 2

Give two advanatges of being an endotherm?

Answer 2

1. They can maintain a fairly constant body temperature despite the external temperature, this means that they can remain active at all times.
2. They are able to inhabit colder parts of the planet.

Question 3

Give two disadvantage of being an endotherm?

Answer 3

1. A large proportion of energy from food in used to maintain body temeprature, therefore they need to eat more than an ecotherm.
2. Less energy from the food is used for growth, so more food must be eaten in order to grow.

Question 4

Give examples of physiological responses used by endotherms in order to regulate their body temperature?

Answer 4

1. Sweat glands. If the body gets too hot the glands secrete more sweat onto the skin. The water in the sweat evaporates using heat from the blood to supply the latent heat of vaporisation. If the body gets too cold, less sweat is secreted, less water is evaporated, therefore less loss of latent heat.
2. Panting. If the body gets too hot then panting increases the evaporation of water form the nose, mouth and lungs, using latent heat as above. If the body gets too cold, the organism does not pant, so less latent heat is lost.
3. Hairs on skin. If the body is too hot, the hairs lie flat to provide little insulation, therefore more heat can be lost by convection and radiation. If the body is too cold, then hairs are raised to trap a layer of insulating hair, rducing the loss of heat from the skin by convection and radiation.
4. Aterioles leading to caplilaries in the skin. If the body gets too hot, vasodilation allows more blood into the capilaries near the skins surface, therefore more heat can be radiated from the skin. If the body gets too cold, then vasoconstriction reduces the blood flow through capilaries near the surface of the skin, therefore less heat is radiated.
5. Liver cells. If the body is too hot, the rate of metbaolism is reduced, less heat is generated from exergonic reactions. If the body is too cold, then the rate of metbaloism is increased, therefore respiration generates more heat, which is transferred to the blood.
6. Skeletal muscles. If the body is too hot, then there will be no spontaneous contractions. If the body is too cold, then there will be spontaneous contractions (shivering) to generate heat from the muscle cells due to respiration (exergonic reaction).

Question 5

Give examples of behavioural responses used by endotherms in order to regulate their body temperature?

Answer 5

1. Move into the shade or hide in a burrow if its too hot. If its too cold move into the sunlight.
2. Orientate body to decrease surface area exposed to the sun if its too hot. If its too cold orientate body to incrase surface area exposed to the sun.
3. Remain inactive if its too hot and spread limbs. Move about to generate heat in muscles. If it’s extremely cold it is best to not move around but huddle.

Question 6

Where in the body is a change in temperature detected? And what happens after a change is detected?

Answer 6

The thermoregulatory centre in the hypothalamus detects the change in blood temperature. After a change is detected the nervous system and hormonal system carry signals to skin, liver and muscles to reverse the changes.

Question 7

What are the role of the peripheral temperature receptors?

Answer 7

The peripheral temperatures are in the skin and monitor the temperatures in the extremities. They act as an early warning system. If they signal to the brain that the external environment is either too hot or too cold, the brain can then initate behavioural mechanisms to regulate the body temperature, without the core temeprature varying by a considerable amount.