Circadian Rhythms A Very Short Introduction PDF Free Download
Circadian rhythms are found in nearly every living thing on earth. They help organisms time their daily and seasonal activities so that they are synchronized to the external world and the predictable changes in the environment. These biological clocks provide a cross-cutting theme in biology and they are incredibly important. They influence everything, from the way growing sunflowers track the sun from east to west, to the migration timing of monarch butterflies, to the morning peaks in cardiac arrest in humans. Despite the diversity of life on our planet, there are many similarities in the way in which circadian rhythms are generated and synchronized to the solar cycle.
There is a molecular feedback loop—the transcription–translation feedback loop (TTFL)—that underpins all these processes, and our understanding of this molecular clockwork provide the best example to date of how genes and their protein products interact to generate complex behaviour. Circadian rhythms are found in bacteria, algae, fungi, plants, and animals, but we have had to concentrate our discussion on mammals. Although rats and mice are familiar, the terminology used to describe the circadian rhythms in these species may be alien to readers, and it is this terminology that makes some of the diagrams seem daunting, but the concepts are, we hope, much easier to follow.