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Humans are normally diurnal creatures that are active in the daytime. As with most other diurnal animals, human activity-rest patterns are endogenously regulated by biological clocks with a circadian (~24-hour) period. [citation needed] Chronotypes have also been investigated in other species, such as fruit flies [1] and mice. [2]
A Young Man Reading by Candlelight, Matthias Stom (ca. 1630). A night owl, evening person, or simply owl, is a person who tends or prefers to be active late at night and into the early morning, and to sleep and wake up later than is considered normal; night owls often work or engage in recreational activities late into the night (in some cases, until around dawn), and sleep until relatively ...
A more stringent study conducted in 1999 by Harvard University estimated the natural human rhythm to be closer to 24 hours and 11 minutes: much closer to the solar day. [87] Consistent with this research was a more recent study from 2010, which also identified sex differences, with the circadian period for women being slightly shorter (24.09 ...
[7] [4] More specifically, geckos, which were thought to be naturally nocturnal have shown many transitions to diurnality, with about 430 species of geckos now showing diurnal activity. [4] With so many diurnal species recorded, comparative analysis studies using newer lineages of gecko species have been done to study the evolution of diurnality.
A circadian rhythm is an entrainable, endogenous, biological activity that has a period of roughly twenty-four hours. This internal time-keeping mechanism is centralized in the suprachiasmatic nucleus (SCN) of humans, and allows for the internal physiological mechanisms underlying sleep and alertness to become synchronized to external environmental cues, like the light-dark cycle. [4]
Humans still don’t need to hibernate, Weiss said, nor can we afford to due to our social and occupational obligations. “But we can make adjustments to perform in a better way, to rest in a ...
[15] In infants , the sleep cycle lasts about 50–60 minutes; average length increases as the human grows into adulthood. In cats , the sleep cycle lasts about 30 minutes, though it is about 12 minutes in rats and up to 120 minutes in elephants (In this regard, the ontogeny of the sleep cycle appears proportionate with metabolic processes ...
The pupil of the eye dilates in the dark to enhance night vision. Shown here is a pupil of an adult naturally dilated to 9 mm in diameter in mesopic light levels. The average human eye is not able to dilate to this extent without the use of mydriatics. Nocturnal mammals have rods with unique properties that make enhanced night vision possible.