Circadian Rhythms affect Living Things

Circadian rhythms are patterns repeating about a day apart. The word, circadian, means about a day. We may be more familiar with monthly or lunar cycles, because women have menstrual cycles monthly (and men, too, have monthly flux in their hormones). But circadian rhythms are quite common: Examples. You can do a lab where you check pulse, breathing rate, body temperature and eye-hand coordination and see some of your own cycles. (Post a comment if you need details.) Plants also have circadian rhythms:

1. Annual Review of Plant Physiology and Plant Molecular Biology. Vol. 52: 139-162 (Volume publication date June 2001) (doi:10.1146/annurev.arplant.52.1.139)
   CIRCADIAN RHYTHMS IN PLANTS by C Robertson McClung .
   
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Math overlaps with science. Here is a Math model for circadian rhythms