Yes...
Did you know the daily biological clock maintains rhythms in many living organisms even in the absence of an apparent environmental stimulus. This so-called circadian (circa= approximately, dian=day) rhythm has a frequency of approximately 24-hours, although in nature it is typically synchronized to exactly 24h by the light/dark or temperature cycles that result from the rotation of the Earth. Within each individual, an orchestra of rhythms conducts essential biological processes. The clock creates an endogenous temporal framework in fungi, plants, and animals, and in at least some bacteria. In the case of humans, the timing program dictates when we sleep and awaken.
It has been estimated that there may be 15 to 30 million species of organisms living on earth. Do all of these have a biological clock? Most organisms are exposed to 24-hour cycles in environmental conditions and they show corresponding cycles in physiology and behaviour. Importantly, when the clock is physically removed or when so-called clock genes are mutated, an organism is out-competed by one with an intact circadian clock, suggesting an evolutionary advantage to a functional daily timing system. We therefore project that endogenous timing systems will be pervasive throughout nature and indeed, circadian clocks have been found in organisms from unicells to , for instance, animals, with established experimental model systems in the bacteria, fungi, plants and animals.
People often ask about organisms that live in ‘constant conditions’ in nature, such as bacteria living around the ‘black smokers’ in the deep ocean or cave fish. Although the environment as concerns light and temperature might be constant in these special niches, there should be echoes of the 24 hour daily cycle that leach into these environs. Anything in the environment that changes with a regular and predictable frequency (food source?) could possibly stimulate evolution of an endogenous temporal structure...?
