Question

The mammals (animals) from colder climates generally have shorter hair and not fully developed ears, eyes, and other phenotypic characters. This is known as
A. Dalla’s Law
B. Allen’s Law
C. Cope’s Law
D. Bergman’s Law

Answer 1

Hint: The surface area of the organism determines the internal homeostasis of the organism. Animals in cold need to retain heat as much as possible. This rule predicts that endothermic animals with the same body volume should have different surface areas that will either aid or impede their heat dissipation.

Complete answer: Animals living in cold usually have a thick coat and thick fur that insulates them from cold temperatures. The polar bear is the best example to study animals living in the cold. The polar bear has thick fur having stocky limbs and very short ears. It was described by Joel Asaph Allen in 1877 as Allen’s Rule. The rule simply states that animals that are adapted to live in cold environments have shorter limbs and bodily appendages that are adapted to cold environments. The principle is based on the fact that the surface area-to-volume ratio for homeothermic animals differs with the temperature of the habitat to which the organisms are adapted. It states that warm-blooded animals tend to have a reduction in the size of legs, bill, tail, etc. in cooler climates. Some examples of Allen’s rule are species of birds like redshank. The length of this bird is reduced to reduce heat loss and provide insulation to control excess cooling of the body.
Therefore, the correct answer is option B.

Note: Differences in limb lengths have also been observed in the human population living in the colder regions. The environment at higher altitudes induces a reduction in limb size of humans. It is evident by the shorter heights of people living in colder regions.