Question

As per Allen’s rule, mammals of cold regions conserve body heat through
A) Larger body mass
B) Small body mass
C) Longer extremities
D) Smaller extremities

Answer 1

Hint:The rule of Allen is an ecogeographical rule established in 1877 by Joel Asaph Allen. While there are several variations, the predictions of Allen 's rule seem to apply to many animal populations.

Complete answer:
Allen’s rule, which broadly states that animals adapted to cold climates have shorter limbs and body appendages than animals adapted to hot climates.
In particular, the body surface-to - volume ratio for homeothermic animals varies with the average habitat temperature to which they are adapted (In cold climates, the ratio is low and in hot climates, it is high).
The rule of Allen predicts that endothermic animals with the same body volume should have different surface areas that either support or impede their heat dissipation. Because animals living in cold climates need to retain as much heat as possible, the rule of Allen predicts that comparatively low surface-to - volume ratios should have evolved to reduce the surface area from which they dissipate heat.The polar bear has stocky limbs and very short ears that are in line with Allen's law predictions.
When different parts of a given human population live at different altitudes, marked variations in limb lengths have been reported. Higher-altitude areas normally experience lower air temperatures.
Individuals living at higher altitudes in Peru appeared to have shorter limbs, whereas those from the same population who lived in the lower coastal areas typically had longer limbs.Therefore, mammals from cold regions maintain body heat by smaller extremities as per Allen's law.

The correct answer is option (D) Smaller extremities.

Note:A contributing factor to the Allen vertebrate rule may be that cartilage growth is at least partly temperature-dependent. Temperature can directly influence cartilage development, providing this rule with a proximate biological explanation.