Circadian rhythms are crucial for co-ordinating an organism’s physiological and behavioural activities with environmental change, such as daily changes in light and temperature. The term ‘circadian’ is derived from circa, meaning about, and diēm , meaning day. Circadian rhythms are controlled by internal clocks that regulate biological processes. They do not require input from the environment in order to generate their cyclical activity, although they do rely on external signals to synchronise their output with environmental changes.
The fruit fly Drosophila melanogaster is an excellent model organism for investigating circadian rhythms. Its genome has been sequenced, and many mutant strains are available that show changes in both physiology and behaviour. This allows precise genetic manipulation and functional analysis of specific genes. Like humans, Drosophila exhibits well-defined behaviours that are controlled by circadian rhythms. Researchers can observe these circadian responses, identify the genes involved, and analyse related neuronal activity in the laboratory.
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