OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the effect of sweat evaporation on body temperature?

1. It raises body temperature

2. It has no effect

3. It cools the body down

4. It can cause dehydration

The correct answer is: It cools the body down

Sweat evaporation has the primary effect of cooling the body down, which is why this is the correct answer. When sweat is produced on the skin's surface, it absorbs heat from the body as it transitions from a liquid state to a gas. This process of evaporation requires energy, which is taken from the body in the form of heat, leading to a decrease in body temperature. This is an essential physiological response, especially during exercise or in hot environments, as it helps maintain homeostasis and prevent overheating. Other effects considered in the options focus on different aspects of sweating and its consequences. While sweating itself does not directly raise body temperature, it plays a critical role in thermoregulation. The notion that it has no effect is inaccurate, as the evaporation process directly contributes to cooling. Lastly, while excessive sweating could potentially lead to dehydration, this is more a consequence of fluid loss than a direct effect of evaporation on body temperature. Therefore, while dehydration is a concern related to sweating, it does not pertain to the immediate impact of sweat evaporation on regulating body temperature.