Extraocular Light Receptors and Circadian Rhythms

Abstract

For organisms to which functioning in time with the solar day is vital, transitions from light to dark or from dark to light are some of the most reliable Zeitgebers or indicators of real time available to them in their physical environments. In its natural habitat, an animal or plant can use such changes to orient itself precisely to the day-night phases of a world which is characterized by many cyclic geophysical variations which influence and affect organisms and their behavior.