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Related to biological clock: circadian rhythm
1. An internal mechanism in organisms that controls the periodicity of various functions or activities, such as metabolic changes, sleep cycles, or photosynthesis.
a. The time period during which a person who desires to have a biological child, especially a woman approaching the decline of reproductive capability, is still able to do so.
b. The capacity to be fertile, especially in such a woman: She was eager to have a child before her biological clock stopped working.
1. (Biology) an inherent periodicity in the physiological processes of living organisms that is not dependent on the periodicity of external factors
2. (Biology) the hypothetical mechanism responsible for this periodicity
1. an innate mechanism of the body that regulates its rhythmic and periodic cycles, as that of sleeping and waking.
2. such a mechanism perceived as inexorably marking the passage of one's youth and esp. one's ability to bear children.
An internal system of organisms that controls the cycle of various functions, such as sleep cycles in mammals and photosynthesis in plants. See Note at circadian rhythm.