Circadian Rhythms

A fascinating segment recently on Radio 4, discussed the impact and importance of circadian rhythm's(what we may describe as the body clock when referring to sleep) however they are not just present in our sleep.

"These rhythms are generated within organisms and also in response to external stimuli, mainly light and darkness. They are found throughout the living world, from bacteria to plants, fungi to animals and, in humans, are noticed most clearly in sleep patterns" 

A link is provided below for you to listen to the full segment