Abstract:
The rotation of the earth about its axis and its revolution around the sun brings about daily and
annual cycles in geophysical processes such as light and temperature. Almost all organisms on earth
excluding those that live under constant aperiodic conditions (such as organisms living in caves,
subterranean habitats and deep seas) need to be able to cope with these changes, and are therefore
believed to have evolved mechanisms to synchronize their behavioural, physiological and
biochemical processes to the periodically changing environment with the help of endogenous timekeeping
mechanisms or clocks (Vaze & Sharma, 2013).
