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Article: Circadian Rhythm
- Article from:
- Animal Sciences
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CopyrightCOPYRIGHT 2002 The Gale Group Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Circadian Rhythm
The circadian rhythm describes the internal biological clock that controls an organism's daily activity cycles. It is well-known that in many species, activity does in fact follow daily patterns. This applies to activities such as feeding or sleeping, as well as to physiological attributes such as metabolic rate, body temperature, blood pressure, and
hormone
levels. Most animal and plant species have daily rhythms and even fairly simple creatures like bacteria have been known to have natural daily cycles.
Experiments in which organisms are placed in constantly light or constantly dark environments frequently indicate that daily periodicity in activity patterns persists ...