Final answer:
Allen's rule is an ecogeographic principle stating that animals in warmer climates have longer extremities to dissipate heat effectively, while those in colder climates have shorter extremities to minimize heat loss.
Step-by-step explanation:
Allen's rule is an ecogeographic rule that explains how the body forms of animals adapt to different climates. The rule states that animals living in hotter climates tend to have longer extremities (like ears, tails, legs, and snouts) compared to closely related animals living in colder climates. This adaptative feature helps animals in warm environments to dissipate heat more effectively, aiding in thermoregulation. Conversely, animals in colder environments have shorter extremities, which helps to reduce heat loss.