ABSTRACT
Circadian (daily) rhythms are biological rhythms that are observed in virtually all eukaryotes [reviewed in 1] and in some prokaryotes [reviewed in 2, 3]. The circadian rhythm we are all most familiar with is our daily sleep-wake cycle. Daily rhythms in biochemical, cellular, and behavioral activities are produced and controlled by a rhythm generator composed of one or more oscillators, herein referred to as the “clock.” The clock generates daily rhythmicity in a wide variety of processes, ranging from the control of development in fungi, cell division in the marine protist Gonyaulax, and photosynthesis in plants, to cognitive functions in people [reviewed in 1].
