Organisms utilize various strategies for regulation of body temperature.

Define the term ectotherm.

Suggest one advantage and one disadvantage that endotherms have compared to ectotherms.

During a class discussion on homeostasis, one student stated:

'Endotherms rely entirely on internal metabolic heat production to regulate their temperature and do not use environmental heat sources.'

Another student stated:

'Ectotherms have no physiological mechanisms to regulate their body temperature; they are completely dependent on behavioral responses.'

Discuss, using examples, whether these two statements are correct.

In response to sudden immersion in cold water, the hormone adrenaline is released into the blood. Adrenaline binds to beta-receptors on the surface of adipocytes (fat cells). This triggers intracellular signalling pathways that activate lipolysis, releasing fatty acids for non-shivering thermogenesis to maintain body temperature.

Suggest two physiological consequences or advantages of activating non-shivering thermogenesis in response to sudden cold exposure.

Adrenaline receptors are located on the cell surface membrane of adipocytes. State two functions of the cell surface membrane that are illustrated by this action of adrenaline.