https://www.sleepfoundation.org/circadian-rhythm

https://en.wikipedia.org/wiki/Circadian_rhythm

From Wikipedia, the free encyclopedia

A circadian rhythm (/sərˈkeɪdiən/), 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.