Decreasing heat loss is important for life in the cold

The coldest habitats on Earth are in the Arctic, the Antarctic, and at the peaks of high mountains. Many birds and mammals, but almost no reptiles or amphibians, live in these places. What adaptations besides endothermy characterize species that live in the cold?

The most important adaptations of endotherms to cold environments are those that reduce heat loss to the environment. Since most heat is lost from the body surface, many cold-climate species have a smaller surface area than their warm-climate cousins, even when their body masses are the same. Rounder body shapes and shorter appendages reduce the

Brown fat occurs in specific anatomical locations.

White fat

Brown fat

41.15 Brown Fat In many mammals, specialized brown fat tissue produces heat.When viewed through a microscope at similar magnifications, we see that white fat cells (left) are simple droplets of lipid with few organelles and limited blood supply, while brown fat cells (right) are packed with mitochondria and richly supplied with blood.

Brown fat occurs in specific anatomical locations.

White fat

Brown fat

41.15 Brown Fat In many mammals, specialized brown fat tissue produces heat.When viewed through a microscope at similar magnifications, we see that white fat cells (left) are simple droplets of lipid with few organelles and limited blood supply, while brown fat cells (right) are packed with mitochondria and richly supplied with blood.

surface area-to-volume ratios of some cold-climate species (Figure 41.16).

Another means of decreasing heat loss is to increase thermal insulation. Animals adapted to cold climates have much thicker layers of fur, feathers, or fat than do their warm-climate relatives. The fur of an arctic fox or a northern sled dog provides such good thermal insulation that those animals don't even begin to shiver until the air temperature drops as low as -20°C to -30°C.

Fur and feathers are good insulators because they trap a layer of still, warm air close to the skin surface. If that air is displaced by water, insulation is drastically reduced. In many species, oil secretions spread through fur or feathers by grooming are critical for resisting wetting and maintaining a high level of insulation.

Decreasing blood flow to the skin is an important ther-moregulatory adaptation in the cold. Constriction of blood vessels in the skin, and especially in the appendages, greatly improves the ability of an animal to conserve heat.

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Essentials of Human Physiology

Essentials of Human Physiology

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  • saundra
    Does the plasma membrane provide thermal insulation?
    7 years ago

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