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Examples include circannual or annual cycles that govern migration or reproduction cycles in many plants and animals, or the human menstrual cycle. Ultradian rhythms , which are cycles shorter than 24 hours, such as the 90-minute REM cycle , the 4-hour nasal cycle , or the 3-hour cycle of growth hormone production.
Examples include circannual or annual cycles that govern migration or reproduction cycles in many plants and animals, or the human menstrual cycle. Ultradian rhythms, which are cycles shorter than 24 hours, such as the 90-minute REM cycle, the 4-hour nasal cycle, or the 3-hour cycle of growth hormone production. [citation needed]
Photoperiodism is the physiological reaction of organisms to the length of light or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods.
Biological rhythms are endogenous; they persist even in the absence of environmental cues as they are driven by an internal mechanism, the circadian clock being the best characterized. Of the several possible cues, known as zeitgebers (German for 'time-givers'), which can contribute to entrainment of the circadian clock, light has the greatest ...
The circadian clock in plants has completely different components to those in the animal, fungus, or bacterial clocks. The plant clock does have a conceptual similarity to the animal clock in that it consists of a series of interlocking transcriptional feedback loops. The genes involved in the clock show their peak expression at a fixed time of ...
A circannual clock mechanism could be similar to the circadian master clock, with an environment-independent timer capable of generating a circannual rhythm in conjunction with a mechanism that keeps the clock entertained to local conditions. [13] Nocturnality is when animals are active during the night, and inactive during the day. This ...
A zeitgeber (/ ˈ (t) s aɪ t ɡ eɪ b ər, ˈ z aɪ t-/ (T)SYTE-gay-bər, ZYTE-, German: [ˈtsaɪtˌɡeːbɐ]) is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.
Post-translational feedback loops (PTFLs) involved in clock gene regulation have also been uncovered, often working in tandem with the TTFL model. In both mammals and plants, post-translational modifications such as phosphorylation and acetylation regulate the abundance and/or activity of clock genes and proteins.