Control of Body Temperature
Temperature is controlled differently in ectotherms and endotherms.
Animals are classed as either ectotherms or endotherms, depending on how they control their body temperature:
Ectotherms – e.g. reptiles, fish
Ectotherms can’t control their body temperature internally – they control their temperature by changing their behaviour (e.g. reptiles gain heat by basking in the sun). Their internal temperature depends on the external temperature (their surroundings). Their activity level depends on the external temperature – they are more active at higher temperatures and less active at lower temperatures. They have a variable metabolic rate and they generate very little heat themselves.
Endotherms – e.g. mammals, birds
Endotherms control their body temperature internally by homeostasis. They can also control their temperature by behaviour (e.g. by finding shade). Their internal temperature is less affected by the external temperature (within certain limits). Their activity level is largely independent of the external temperature – they can be active at any temperature (within certain limits). They have a constantly high metabolic rate and they generate a lot of heat from metabolic reactions.
Mammals have Many Mechanisms to Change Body Temperature
Heat loss mechanisms:
Sweating – more sweat is secreted from sweat glands when the body is too hot. The water in sweat evaporates from the surface of the skin and takes heat from the body. The skin is cooled.
Hairs lie flat – mammals have a layer of hair that provides insulation by trapping air (air is a poor conductor of heat). When it’s hot, erector pili muscles relax so that the hairs lie flat. Less air is trapped, so the skin is less insulated and heat…