<p><a href="https://www.sleepfoundation.org/circadian-rhythm"
class="uri">https://www.sleepfoundation.org/circadian-rhythm</a></p>
<p><a href="https://en.wikipedia.org/wiki/Circadian_rhythm"
class="uri">https://en.wikipedia.org/wiki/Circadian_rhythm</a></p>
<p>From Wikipedia, the free encyclopedia</p>
<p>A circadian rhythm (/s&#x259;r&#x2C8;ke&#x26A;di&#x259;n/), or circadian cycle, is a natural
oscillation that repeats roughly every 24 hours. Circadian rhythms can
refer to any process that originates within an organism (i.e.,
endogenous) and responds to the environment (is entrained by the
environment). Circadian rhythms are regulated by a circadian clock whose
primary function is to rhythmically co-ordinate biological processes so
they occur at the correct time to maximise the fitness of an individual.
Circadian rhythms have been widely observed in animals, plants, fungi
and cyanobacteria and there is evidence that they evolved independently
in each of these kingdoms of life.</p>
