According to Allen's rule, mammals from colder climates generally have shorter ears and limbs to minimise heat loss. Polar seal have a thick layer of fat (blubber) below their skin that acts as an insulator and reduces loss of body heat.
In the absence of an external source of water, the kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation. It exhibits physiological adaptation. Desert lizards show behavioural adaptation. They bask in the sun and absorb heat when their body temperature drops below the comfort zone, but move into shade when the ambient temperature starts increasing. Marine fishes at depth are adapted biochemically to survive in great depths in ocean.

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