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  Chronobiology (from Greek chronos, ‘time’ + biology), in the life sciences, is the study of the control of living systems through time. All biological events occur over a course of time, but a great number occur in a cyclical fashion, with a period which can vary from microseconds (as in the beating of a wing) to a year (as in a mating season). There are two categories of such phenomena: those which are correlated with environmental periodicity (see biological rhythm), and those which appear to be independent of the environment. A characteristic of environmentally correlated rhythms is that they resist alteration, wether by drugs or the removal of environmental factors, they will arise spontaneously (in eggs laid in the laboratory, for example), and they are not dramatically affected by temperature. Evidence suggests the presense of an internal biological clock, in all plants and animals, which is capable of allowing rhythmic phenomena to be precisely controlled, provided the clock is regularly given the chance to synchronize itself with the environment. Investigation of the clock mechanism is particularly challenging because it is difficult to separate components of the clock from the functions it controls. RB

See also phenology.



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