According to Bergmann’s rule, which trait is advantageous in a cold climate?
A. Smaller body size
B. Equiaxed shape
C. Larger body size
D. Elongated shape
The correct answer and explanation is:
The correct answer is C. Larger body size.
Bergmann’s rule states that in colder climates, animals tend to have larger body sizes compared to their counterparts in warmer climates. This principle is based on the relationship between body size and heat retention. Larger animals have a smaller surface area-to-volume ratio, which means they lose heat more slowly and are better able to conserve body heat in cold environments.
The reasoning behind this is that heat loss is proportional to the surface area, while heat production is proportional to body volume. Therefore, animals with larger bodies have more volume to generate heat, and their smaller surface area minimizes heat loss. This adaptation helps them survive and thrive in colder temperatures by maintaining a more stable internal temperature.
For example, larger-bodied species of mammals like polar bears, moose, and bison are more common in colder regions. They exhibit traits that support heat retention, such as thick fur and fat layers, in addition to their larger body size.
In contrast, in warmer climates, smaller body sizes are more advantageous. Smaller animals have a larger surface area relative to their volume, which facilitates heat dissipation, helping them stay cool in hot environments. This adaptation allows them to avoid overheating.
Bergmann’s rule is just one aspect of how animals adapt to their environments. It is a general rule, and exceptions exist. However, it is widely observed in many species, especially among endothermic (warm-blooded) animals, such as mammals and birds.