|1.||an inherent periodicity in the physiological processes of living organisms that is not dependent on the periodicity of external factors|
|2.||the hypothetical mechanism responsible for this periodicity|
|the offspring of a zebra and a donkey.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
biological clock n.
An innate mechanism in living organisms that controls the periodicity or rhythm of various physiological functions or activities.
body clock n.
An internal mechanism of the body that is thought to regulate physical and mental functions in rhythm with normal daily activities.
|biological clock (bī'ə-lŏj'ĭ-kəl) Pronunciation Key
An internal system that controls an organism's circadian rhythms, the cycles of behavior that occur regularly in a day. In mammals, the biological clock is located near the point in the brain where the two optic nerves cross. In many birds, the biological clock is located in the pineal gland. In protists and fungi, the individual cells themselves regulate circadian rhythms.
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.