Thermoregulation In Ectotherms

What are organisms constantly heating up and cooling down as a result of?

Their surroundings.

What do changes in temperature depend on?

A number of physical responses:

• Exothermic chemical reactions.

• Latent head of evaporation.

• Radiation.

• Convection.

• Conduction.

What is convection?

The heating and cooling down of currents of air or water, warm air or water rises and cooler air or water sinks, setting up convection currents around an organism.

What is conduction?

Heating as a result of the collision of molecules. Air is not a good conductor of heat, but the ground and water are.

In many cases, what does the balance between heating and cooling determine?

The core temperature of the organism.

What are ectotherms?

Organisms that use their surroundings to warm their bodies. Their core body temperature is heavily dependent on their environment.

Do many ectotherms living in water need to thermoregulate?

No, because the high heat capacity of water means that the temperature of their environment does not change much.

Do ectotherms living on land need to thermoregulate?

Yes, since the temperature of air can vary dramatically between the seasons and even during the day.

Can ectotherms control their body temperature using their metabolism?

No, however, they have adapted a range of behavioural responses that enable them to overcome the limitations imposed by the temperature of their surroundings.

What do ectotherms display a number of behaviours in order to do?

Increase or reduce the radiation they absorb from the sun.q

What may an ectotherm need to warm up enough for?

To reach a temperature at which their metabolic reactions can be fast enough for them to be active.

How may an ectotherm change their behaviour to increase their temperature?

They may bask in the sun, orientate their bodies so that the maximum surface area is exposed to the sun, and even extend areas of their body surface area to increase the surface area exposed to the sun.

What is another behavioural adaptation ectotherms can use to increase their body temperature?

Through conduction: pressing their bodies against the warm ground. They can also get warmer as a result of exothermic metabolic reactions.

What are specific examples of ectotherms’ behavioural responses to needing to raise body temperature?

• Galápagos iguanas will contract their muscles and vibrate, increasing cellular metabolism.

• Moths and butterflies may vibrate their wings to warm their muscles before they take flight.

What might ectotherms need to cool down in order to prevent?

Their core temperature reaching a point where enzymes begin to denature.

To cool down, what behaviours are employed?

• Lying in the shade, rather than the sun.

• Hiding in cracks, rocks or even digging burrows.

• Pressing their bodies against cool, shady earth and stones.

• Orientating their bodies so that the minimum surface area is exposed to the sun.

• Minimising movement.

What other responses do ectotherms have?

Physiological responses.

What are the physiological adaptations of ectotherms?

• Dark colours absorb more radiation than light colours, so lizards living in colder climates tend to be darker than those living in warmer climates.

• Some ectotherms also alter their heart rate to increase or decrease the metabolic rate and sometimes to affect the warming or cooling across the body surfaces.

Are ectotherms or endotherms more vulnerable to fluctuations in the environment?

Ectotherms. However, by using a variety of behavioural andE physiological strategies, many of them can maintain relatively stable core temperatures.

Do ectotherms or endotherms need less food?

Ectotherms, as they use less energy regulating their temperatures, and so they can survive in some very difficult habits where food is in short supply.