Biological clock may refer to:
- Circadian rhythm, living organisms' adaptations to solar related rhythms
- Age and female fertility
Famous quotes containing the words biological and/or clock:
“Man’s biological weakness is the condition of human culture.”
—Erich Fromm (1900–1980)
“He makes his voyage too late, perhaps, by a true water clock who delays too long.”
—Henry David Thoreau (1817–1862)