Q.Define 'Bergmenn's rule'.

Bergmann's rule states that endothermic animals tend to be larger-bodied in colder climates than in warmer climates, because a larger body conserves heat more efficiently.

Bergmann's rule is a widely observed eco-geographic pattern in warm-blooded (endothermic) species: populations or closely related species living at higher latitudes/colder climates tend to have a larger average body size than those living in warmer, lower-latitude regions. The explanation lies in basic surface-area-to-volume geometry: as body size increases, volume (and hence heat-generating metabolic tissue) increases faster than surface area (through which heat is lost to the environment). A larger animal therefore has a proportionately smaller surface area relative to its volume, reducing the rate of heat loss per unit body mass and helping it conserve body heat in cold environments -- a thermoregulatory advantage. This is why, for example, polar/temper …