What is the term for the biological cycle connected to the Earth's 24-hour rotation?

The term that refers to the biological cycle linked to the Earth's 24-hour rotation is circadian rhythm. Circadian rhythms are natural, internal processes that follow a roughly 24-hour cycle, influencing various physiological and behavioral patterns such as sleep-wake cycles, hormone release, and body temperature. These rhythms are governed by external cues, primarily light, which helps to synchronize them with the day-night cycle.

Circadian rhythms are crucial for maintaining the body's internal clock and ensuring that physiological processes occur at the optimal times for health and functionality. The term "biological clock" is often associated with this concept, but circadian rhythm specifically refers to the 24-hour cycle aspect. Ultradian rhythms, on the other hand, are cycles that occur more frequently than once a day, and infradian rhythms are those that occur less frequently than once a day, such as menstrual cycles. Understanding circadian rhythms can provide insights into various health-related issues, including sleep disorders and the effects of shift work on health.