Waking, and Blooming, in Rhythm

These timing systems dictate when plants will bloom, force people to fall asleep at their desks, urge birds to fly south, and influence a host of other activities. While circadian rhythms run on a 24-hour clock, others also exist, including tidal, lunar, and annual rhythms.

A lot; from bread molds to humans. Well-studied rhythms include those in cyanobacteria, the bread mold Neurospora crassa, rice, Arabidopsis, fruit flies, mice, Syrian hamsters, and humans. Some researchers say that the mechanisms found in rice and Arabidopsis might be the same ones found in all plant species. The clock components found in mice and humans also might be universal for all mammals. While all organisms share the same basic mechanism, the individual components differ, suggesting that clocks evolved independently.

Light sets and resets them, but temperature plays a role, too. Cryptochromes, blue-light detectors found in almost all organisms, transmit signals to circadian genes and ...