One type of a biological rhythm is circadian rhythm.
Circadian rhythm: a cycle, such as sleeping and waking, that occurs daily
The daily cycle of sleeping and waking is influenced by external cues in animals. However, experiments have shown that many animals have an internal clock, often referred to as a biological clock, that maintains the daily rhythm of the sleep/wake cycle of about 24 hours.
Other types can be seasonal or yearly. These cycles are influenced by environmental factors such as temperature changes, the increase or decrease of daylight hours, and the availability of food and water.
