Circadian rhythm

Circadian rhythm is the name given to the roughly 24 hour cycles shown by physiological processes in plants and animals. (The term circadian comes from the Latin circa, meaning "around" and dies, "day", meaning literally, "around a day.") It was initially discovered in the movement of plant leaves in the 1700s by the French scientist Jean-Jacques d'Ortous de Mairan. For a description of circadian rhythms in plants by de Mairan, Linnaeus, and Darwin see http://www.hhmi.org/biointeractive/museum/exhibit00/02_1.html. The formal study of biological temporal rhythms (such as daily, weakly, seasonal, etc.) is called chronobiology.

Related Topics:
Latin - Jean-Jacques d'Ortous de Mairan - Chronobiology

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The circadian rhythm is neither fully dependent on nor fully independent of external cues such as sunlight and temperature. Early researchers identified that some sort of "internal" rhythm must exist, because plants and animals did not react immediately to artificially-induced changes in daily rhythms. However it has been well established that a mechanism for adjustment also exists, as plants and animals will eventually adjust their internal clock to a new pattern (if it is sufficiently regular).

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