Diurnal rhythms are biological rhythms that occur within a 24-hour period, typically following a daily cycle. Many physiological processes, such as sleep-wake cycles, body temperature, hormone secretion, and certain behaviors, exhibit diurnal rhythms. These rhythms are influenced by external cues called zeitgebers, mainly the light-dark cycle.
Circadian rhythms, on the other hand, refer to the body's internal biological clock that controls various physiological and behavioral processes in a 24-hour cycle, even in the absence of external cues. The term "circadian" comes from the Latin words "circa" (around) and "diem" (a day), emphasizing the inherent 24-hour nature of these rhythms. While circadian rhythms can be influenced by external cues such as light and social interactions, they persist even without these cues, making them endogenous processes.
Free-running rhythms are a specific type of circadian rhythm where an organism's biological clock is not influenced by external cues. In a completely isolated environment without any external time cues, such as artificial light or social interactions, an organism with a free-running rhythm would exhibit a consistent cycle that is not necessarily synchronized with the natural 24-hour day. This can lead to deviations from a typical sleep-wake cycle, hormone secretion, and other physiological processes. Studying free-running rhythms can help understand the inherent biological timing mechanisms within organisms.
4. Distinguish between diurnal, circadian and free�running rhythms.
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