Which of the following would increase the rate of heat exchange between an animal and its environment? A vasoconstriction
B wind blowing across the body surface
C countercurrent heat exchanger
D feathers or fur
The correct answer and explanation is:
Correct Answer: B. Wind blowing across the body surface
Explanation (300 words):
Heat exchange between an animal and its environment occurs through processes such as conduction, convection, radiation, and evaporation. The rate at which heat is transferred depends on factors like surface area, temperature gradient, and insulation.
Option B: Wind blowing across the body surface increases the rate of convective heat loss. When wind passes over the body, it removes the warm air layer close to the skin and replaces it with cooler air. This maintains a higher temperature gradient between the body surface and the surrounding air, allowing heat to be lost more rapidly. Additionally, if the skin is moist (e.g., through sweating), wind also enhances evaporative cooling, further increasing heat loss. Therefore, this option directly increases heat exchange.
Let’s consider why the other options do not increase heat exchange:
- Option A: Vasoconstriction is the narrowing of blood vessels near the body surface. It reduces blood flow to the skin, minimizing heat loss by keeping warm blood away from the cooler external environment. This decreases the rate of heat exchange, not increases it.
- Option C: Countercurrent heat exchanger is an adaptation found in some animals (like penguins or whales) that helps retain heat. Warm blood flowing from the core passes heat to cooler blood returning from the extremities, reducing heat loss to the environment. This system conserves heat rather than promoting exchange with the environment.
- Option D: Feathers or fur provide insulation, trapping air close to the body and reducing heat flow. This is essential for maintaining body temperature in cold environments. However, it acts as a barrier to heat transfer and decreases heat exchange.
In conclusion, among the choices, wind blowing across the body surface is the only factor that clearly increases the rate of heat exchange between an animal and its environment.