5.1.3: Temperature control in ectotherms Flashcards
Why is the core temperature more important than the temperature of the peripheral parts of the body?
Because all vital organs are found at the centre of the body, peripheral temperatures can increase or decrease with to some extent without affecting the survival of the organism.
What is an endotherm?
- They control their body temperature within very strict limits.
- They use a variety of mechanisms to control body temperature and are largely independent of external temperature.
What is an ectotherm?
- They are not able to control their body temperature as effectively as endotherms.
- They rely on external sources of heat and their body temperature fluctuates with the external temperature.
- HOWEVER, using behavioural mechanisms, some ectotherms are able to control their body temperature on all but the most extreme conditions.
Ectotherms do not use internal energy sources to maintain their body temperature when cold. However, once they are active, what happens?
Their muscle contractions will generate some heat from increased respiration.
What does temperature regulation in ectotherms rely on?
behavioural responses that can alter the amount of heat exchanges with the environment.
If ectotherms are not warm enough, what do they do?
They try to absorb more heat from the environment by:
- moving into the sun.
- lying on a warm surface.
- exposing a larger surface are to the sun.
If ectotherms are too hot, what do they do?
They try to avoid gaining more heat from the environment and they try to increase heat loss to the environment, they…
- move out of the sun.
- move underground.
- reduce body surface exposed to the sun.
Snakes bask in the sun, what is the benefit of this behavioural adaptation?
Absorbs heat directly from the sun.
Locusts:
-early morning, sit side-on to the sun.
-midday, they face the sun head-on.
-they may also climb to the top of a plant at midday to get away from the soil.
what is the benefit of these behavioural adaptations?
- In the cool mornings, they can absorb more heat by exposing a large surface area.
- at midday, when the sun is hotter, they absorb less heat by exposing a smaller surface area.
- the soil surface gets hot and radiates heat; if the locust moves away from the soil it gains less heat from the soil.
Locusts also increase both the rate of breathing and depth of breathing movements when it is hot, what is the benefit of this behavioural adaptation?
More water evaporates from the tracheal system, cooling the body.
Many lizards use burrows or crevices between rocks. They hide in these burrows during the hottest art of the day and the coolest parts of the night. What is the benefit of this behavioural adaptation?
- an underground burrow tends to have a more stable temperature than air.
- In the hottest part of the day, it will be cooler in the burrow.
- At night, the burrow may be warmer than the air outside.
A horned lizard can change its shape by expanding or contracting its ribcage, what is the benefit of this behavioural adaptation?
Expanding ribcage increases the surface area exposed to the sun so more heat can be absorbed.
What are the advantages of ectothermy?
Ectotherms rely on external heat sources to keep warm. They do not use up energy to keep warm. therefore:
- less of their food is used in respiration.
- more of the energy and nutrients gained from food can be converted to growth.
- they need to find less food.
- They ca survive for long periods without food.
What are the disadvantages of ectothermy?
- they are less active at cooler temperatures.
- this means that they are at risk from predators while they are cold and unable to escape.
- they cannot take advantage of food that is available while they are cold.
