Part 5: Endotherms and Ectotherms

What are ectotherms? How do the control their temperature? Give 3 examples

• Ectotherms ("cold-blooded" animals) are organisms whose body temperature fluctuates with the temperature of their environment.

• They mainly rely on behaviour (e.g. moving into the sun or shade) to control their body temperature.

Examples: Lizards, snakes and frogs.

How do ectotherms respond to hot and cold conditions?

• In cold conditions, ectotherms become sluggish because enzyme activity slows down. They may need to hibernate to avoid freezing.

• In hot conditions, they remain active but may aestivate in very hot or dry conditions.

Aestivation: Summer hibernation in which an organism becomes dormant or inactive.

What are the advantages and disadvantages of ectotherms?

Advantages:

• Require less energy and therefore less food.

Disadvantages:

• Can become easy prey when inactive

What are endotherms?

Endotherms ("warm-blooded" animals) are birds and mammals that maintain a constant body temperature regardless of environmental temperature

How do endotherms maintain a constant body temperature?

Endotherms use thermoregulation mechanisms, including:

• Vasodilation

• Vasoconstriction

• Sweating

• Shivering

These mechanisms help keep body temperature constant.

How do endotherms respond to hot and cold conditions? Why?

Endotherms remain active in both hot and cold conditions. This is because endotherms maintain a relatively constant body temperature, so their enzymes continue to function at or near their optimum temperature.

Note: Only small mammals hibernate, and endotherms do not usually aestivate.

What is the main disadvantage of endotherms?

Endotherms require a lot more food because maintaining a constant body temperature uses a large amount of energy.

(Main advantage = active in all conditions)