Abstract:
The Earth rotates around its axis creating alternate day/night cycles to which almost all
organisms have adapted to create for themselves a distinct spatio-temporal niche (Pittendrigh,
1993; Sharma, 2003; Dunlap et al., 2004; Paranjpe and Sharma, 2005; Vaze and Sharma, 2013).
It is widely believed that fluctuations in geophysical factors have aided the evolution of rhythms
of a wide range of periodicities - tidal (~12 hours), semilunar (~14 days), lunar (~29 days) and
annual (~a year) time scales. Among the variety of biological oscillations present in the living
world, the most ubiquitous and hence the most widely studied ones are those with circadian
periodicities (circadian rhythms: Latin: circa - approximately, dies - a day).
Circadian clocks time the day-to-day behavioral repertoire of organisms and coordinate
cellular and molecular cycles to ensure that they occur at suitable times of the day (Sharma,
2003; Paranjpe and Sharma, 2005; Vaze and Sharma, 2013). These clocks are known to
synchronize metabolic processes with the environmental cycles to enable organisms to anticipate
cyclic changes in their environment (Pittendrigh, 1993; Sharma, 2003; Dunlap et al., 2004; Vaze
and Sharma, 2013).
