Definition: The biological clock is the mechanism found within living organisms that coordinates the timing of physiological functions and behaviors to the natural day-night cycle.
The master clock is within the suprachiasmatic nucleus, a small region of the brain, and exerts hormonal control to peripheral clocks that have been described in many cell types. Coordination of these rhythms is believed to allow maximal use of resources, access to food, and protection from predators across species.
Examples: The biological clock controls the body's activities through the release of hormones based on the time of day.
