Ans. The biological rhythms are mainly classified based on their function routine. They are classified into four types namely, circadian rhythms, diurnal rhythms, ultradian rhythms, and infradian rhythms. The circadian rhythm takes 24 hours cycle and it takes responsibility for physiological and behavioural changes like sleeping, eating..etc. Diurnal rhythms help to syncs the day and night for circadian rhythm, it also adjects according to the environment clues. Ultradian rhythms last for the shortest period at high frequency. Infradian rhythms last for more than 24 hours. The best example of the infradian rhythms is the menstrual cycle. Usually, mutation or changes in certain genes impact biological rhythms. Shift work and light from electronic devices also affect biological rhythms.