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In warm-blooded or homeothermic (constant temperature) animals, body temperature is carefully regulated. The hypothalamus, located in the brain, acts as the master thermostat to keep body temperature constant to within a fraction of a degree Celsius in a healthy animal. If the body temperature starts to deviate much from the desired constant level, the hypothalamus causes changes in blood flow and initiates other processes, such as shivering or perspiration, to bring the temperature back to normal. Why is this careful temperature regulation necessary? What would be the problem if body temperature fluctuated with environmental conditions? What evolutionary advantage does a constant body temperature give the warm-blooded animals (birds, mammals) over the cold-blooded (such as reptiles and insects)? What are the disadvantages?
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