biological clock

biological clock   n.   An internal mechanism in organisms that controls the periodicity of various functions or activities, such as metabolic changes, sleep cycles, or photosynthesis. The progression or time period from puberty to menopause, marking a woman's ability to bear children.

biological clock

The innate rhythm of behavior and body activity in living things. A twenty-four-hour cycle of body activity, which operates in some organisms, is called the circadian rhythm.

Note: Although the term biological clock refers to all innate timing mechanisms, it is often used when describing certain body functions that are subject to this rhythm, such as the loss of fertility with age.

Main Entry: biological clock
Function: noun
: an inherent timing mechanism in a living system (as a cell) that is inferred to exist in order to explain various cyclicalbehaviors and physiological processes

biological clock n.
An innate mechanism in living organisms that controls the periodicity or rhythm of various physiological functions or activities.