ABSTRACT
Depending on where you are on our planet, the environment can change considerably during the course of the day night cycle. For this reason adaptations to time-of-day dependent changes in for example sunlight, temperature, food availability and predation are critical for the survival of organisms. The circadian clock plays an essential role in these adaptations by enabling organisms to anticipate environmental changes. Most aspects of physiology are controlled by this clock and consequently show circadian rhythms. Since it is not a precise 24-hour timer, it requires daily resetting by environmental cues such as light and temperature to ensure it remains synchronized with the day-night cycle. However, the clock also continues to function (“free-run”) under artificial, constant conditions (Pittendrigh, 1993).
