Maintaining Body Temperature

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f) Describe the physiological and behavioural responses that maintain a constant core body
temperature in ectotherms and endotherms.
Ectotherm: an organism that relies on external sources of heat to regulate its body
use less food in respiration.
need less food and may be able to survive for long periods without eating.
a greater proportion of the energy obtained from food can be used for growth.
less active in cooler temperatures; may need to warm up in the morning before they can be
active, which puts them at greater risk of predation.
they may not be capable of activity during the winter, as they can't warm up sufficiently. So
they must have sufficient stores of energy to survive on over the winter without eating.
When cold, ectotherms will change their behaviour or physiology to increase absorption of
heat from its environment.
When hot, they will change their behaviour or physiology to decrease absorption of heat
and increase loss of heat to its environment.
Behavioural Adaption How it regulates temp. Example
Expose body to sun More heat can be absorbed Snakes
Orientate body to sun Larger surface area exposed Locusts
for more heat absorption
Orientate body away from sun Lower surface area exposed Locusts
so less heat absorbed
Hide in burrow Reduces heat absorption Lizards
Alter body shape More/less surface area Horned Lizards
exposed to sun
Increase breathing Evaporates more water Locusts
Endotherm: an organism that can control production and loss of heat to maintain their
body temperature.
have fairly constant body temperature.
activity is possible in cool external temperature.
have ability to inhabit colder parts of planet.
significant part of energy intake used to maintain body temperature in the cold.
more food is required.
less energy from food is available for growth.
Endotherms monitor the temperature of their blood in the hypothalamus of the brain.

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If core temperature drops below the optimum, the hypothalamus sends signals to reverse
the change ­ increased rate of metabolism, release heat through extra muscular contraction
and decrease loss of heat to the environment.
If the core temperature rises above the optimum, the hypothalamus sends signals to bring
about the opposite changes (negative feedback).
It's the thermoregulatory centre in the hypothalamus that monitors blood temperature and
detects and changes in the core body temperature.…read more


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