This can be related to living things adapting to various climates. Endotherms or warm-blooded animals like mammals and birds, regulate their own body temperature. Allen's rule states that endotherms will have shorter appendages in colder climates, versus those in warmer climates. In colder climates, the more surface area exposed equals greater loss of heat. These organisms need to conserve heat energy to be able to survive. However, organisms in warm climates may overheat, thus they have a high surface area to volume in order to help them lose heat. Consider an African elephant's ears. These are huge and actually help to radiate excess heat, as there are blood vessels permeating these appendages and hot loss occurs between the ears and the surroundings. Polar bears however, have stocky limbs and short ears to help minimize how much heat is radiated out of the body in cold climates.