[Evolution of sleep].

Evolution is a continuous process that changes population genetics towards greater adaptation. Sleep is an example of a conservative trait that appears everywhere and is regulated similarly in the animal kingdom. Because of this similarity in sleep regulation different animal models and genetic modification can be used in basic research and in studies of sleep related diseases. Recent research has enlightened the function of the clock genes and the synaptic plasticity during sleep, so that we can better understand the need for sleep and the effects of sleep loss. This knowledge is needed in order to prevent and treat sleep related diseases.