predictable fluctations resulting from seasons, time of day, etc.
cycles can link to patterns operating at different time frames: circadian (24h period length), ultradian (>24h), tidal (12.4h), lunar (24.8h), circannual (12months); exogenous vs. endogenous cycles
Description of a rhythmic pattern: sequence of events which repeat in cyclical fashion, cycle, frequency, amplitude
Biological clocks are self sustaining oscillators, that is linked to and can be reset by the environment
output pathway(s) through which the pacemaker regulates various output rhythms
periodic expression of immediate early genes (IEG), period (per) and timeless (tim) genes control each other through transcription-translation autoregulatory feedback loop in Drosophila
Pineal gland, and Melatonin in photoperiod
Mammalian suprachiasmatic nucleus or SCN
Reading Assignment
Chapter 9: Biological Rhythms. pp 142-156
Food for Thought
Why does the ruby-throated hummingbirds migrate from Ohio to
Belize and back?
