Answer any two of (a), (b), (c) - Leaving Cert Biology - Question 15 - 2006

An endotherm is an organism that maintains a constant body temperature, regardless of external environmental conditions. This means that the human body can regulate its own temperature through various physiological processes.

The primary source of body heat in endotherms comes from metabolic processes, primarily through the breakdown of carbohydrates and lipids, or from cellular respiration within the liver and muscles.

The sweat gland (D) plays a crucial role in thermoregulation by producing sweat, which evaporates from the skin's surface, facilitating heat loss and helping to cool the body during high temperatures or physical exertion.

When the external temperature drops, the small arteries (arterioles) in the skin constrict. This process, known as vasoconstriction, helps to reduce blood flow to the skin, minimizing heat loss and maintaining the body's core temperature.