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Body activities are influenced by body temperature. Enzyme activity typically rises along with
body temperature. The activity of enzymes doubles up to a certain
point for every ten degrees
centigrade increase in temperature. High heat causes body proteins, including enzymes, to denature
and lose their functionality (around 50oC for mammals). With a few exceptions, enzyme activity will
decrease by 50% for every ten degrees centigrade drop in temperature up to freezing. Some fish can
withstand freezing solid and return to normal with thawing. Watch this Discovery Channel video on
thermoregulation to see illustrations of this process in a variety of animals

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Heat Conservation and Dissipation
Animals use a variety of techniques to store or release heat.
Endothermic animals have
insulation in some climates, such as fur, fat, feathers, or a combination of these. Skin and internal
organs are insulated from one another by air in animals with thick fur or feathers. Polar bears and
seals can swim and live in subfreezing temperatures while still maintaining a constant, comfortable
body temperature. When the arctic fox curls up to sleep in cold weather, for instance, it uses its fluffy
tail as additional insulation. Shivering and increased muscle activity
have a lasting effect on
mammals: when a person is cold, their arrector pili muscles produce "goose bumps," which cause
small hairs to stand up. This has the intended effect of raising body temperature. Layers of fat are
used by mammals to accomplish the same goal. Loss of significant
amounts of body fat will
compromise an individual’s ability to conserve heat

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