what is a circadian rhythm?
What are circadian rhythms? Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment. They are found in most living things, including animals, plants and many tiny microbes. The study of circadian rhythms is called chronobiology.
Although the circadian pacemaker does not generate each and every rhythm individually, the causal connections between different rhythms are not fully known. It is known that the rhythm of body temperature is not caused either by the rhythm of activity or by the rhythm of feeding. Body temperature is under both homeostatic control and circadian control.