Homeostasis

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Homeostasis (from Greek: ὅμοιος, hómoios, "similar"[1] and στάσις, stásis, "standing still";[2] defined by Claude Bernard and later by Walter Bradford Cannon in 1926[3], 1929[4] and 1932[5][6]) is the property of a system, either open or closed, that regulates its internal environment and tends to maintain a stable, constant condition. Typically used to refer to a living organism, the concept came from that of milieu interieur that was created by Claude Bernard and published in 1865. Multiple dynamic equilibrium adjustment and regulation mechanisms make homeostasis possible.

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Biological

With regards to any given life system parameter, an organism may be a conformer or a regulator. On one hand, regulators try to maintain the parameter at a constant level over possibly wide ambient environmental variations. On the other hand, conformers allow the environment to determine the parameter. For instance, endothermic animals (mammals and birds) maintain a constant body temperature,while exothermic animals (almost all other organisms) exhibit wide body temperature variation.

Behavioral adaptations allow endothermic animals to exert some control over a given parameter. For instance, reptiles often rest on sun-heated rocks in the morning to raise their body temperature. Regulators are also responsive to external circumstances, however: if the same sun-baked boulder happens to host a ground squirrel, the animal's metabolism will adjust to the lesser need for internal heat production.

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