Organisms utilize different ecological and physiological strategies to manage their thermal energy budget.

Define the term endotherm.

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

During a classroom debate on physiological regulation, one student asserted:

'Endothermic organisms maintain a perfectly constant internal core body temperature, which is entirely independent of any behavioral adjustments.'

Another student claimed:

'Ectothermic organisms cannot regulate their internal temperature at all when there is no direct sunlight, relying solely on solar radiation to prevent freezing.'

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

Under conditions of acute cold stress (such as a newborn mammal entering a cold extrauterine environment), the sympathetic nervous system releases the hormone noradrenaline. Noradrenaline binds to specific beta-3 adrenergic receptors on the cell surface membrane of brown adipocytes (brown fat cells). This triggers an intracellular cascade that activates uncoupling protein 1 (UCP1) in mitochondria, initiating non-shivering thermogenesis to generate heat.

Suggest two physiological advantages of utilizing non-shivering thermogenesis in brown adipose tissue rather than shivering in skeletal muscles for a newborn mammal.

Noradrenaline receptors are located on the cell surface membrane of brown adipocytes. State two functions of the cell surface membrane that are illustrated by this action of noradrenaline.