As humans we live our lives in 24-hour increments—waking, eating, and sleeping at specific times dictated to us not solely by our discerning willpower, but also by the greater underlying persuasion of our circadian rhythm. Based on the earth’s rotation from day into night, we have internalized a deeply rooted clock that drives how we behave in response to our genetic expression patterns. It’s not hard to imagine that several other organisms respond to an internal sense of time. Sure enough, the 24-hour circadian rhythm is a highly conserved behavior—from complex mammals down to plants, fungi, and cyanobacteria. Interestingly, there are also examples of different temporal rhythm patterns—ranging from years and seasons to minutes and seconds. A curious example is that of the bacterium Paenibacillus dendritiformis, which seems to have its own internal clock of a mere 20 seconds.
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