Question

Small mammals and birds are rarely found in polar regions. The reason is that

• A. They have a larger surface area relative to their volume
• B. They tend to gain heat very fast
• C. They expend less energy to generate body heat
• D. None of the above

Answer 1

The Correct Option is A

The question asks why small mammals and birds are rarely found in polar regions. The correct explanation for this phenomenon lies in their biological characteristics, specifically related to their body structure and thermoregulation.

The correct answer is: They have a larger surface area relative to their volume.

Let's explore why this is the correct answer by breaking down the reasoning:

• Small mammals and birds have a relatively larger surface area compared to their body volume. This is due to the basic geometric law where, as the size of an animal decreases, the surface area to volume ratio increases.
• In colder climates, like polar regions, maintaining body heat is crucial for survival. Animals with a larger surface area relative to their volume lose heat more rapidly than they can produce it because a greater surface area means more heat is lost to the surrounding environment.
• As a result, small mammals and birds struggle to generate enough body heat to keep themselves warm in extremely cold environments like the polar regions, which makes them rare in such areas.
• This explains why larger creatures with smaller surface area to volume ratios, like polar bears and seals, are more commonly found in polar environments since they can retain heat more effectively.

Ruling out other options:

• They tend to gain heat very fast: In polar regions, the primary challenge is retaining heat, not gaining it quickly from the environment, which is extremely cold.
• They expend less energy to generate body heat: Small mammals and birds usually have high metabolic rates to generate body heat, contrary to this statement.
• None of the above: Clearly, the correct anatomical-biological reasoning is due to their larger surface area to volume ratio.

In summary, the primary reason smaller animals such as small mammals and birds are rare in polar regions is their relative difficulty in maintaining body heat due to a high surface area to volume ratio, leading to excessive heat loss.