15. define circadian rhythms. provide two examples of circadian rhythms.

Brief Explanations:

Circadian rhythms are internal biological processes that follow a roughly 24 - hour cycle. They are regulated by the body's internal clock (suprachiasmatic nucleus in the hypothalamus) and are influenced by external cues like light - dark cycles. For the example of sleep - wake cycle: Most humans follow a pattern of sleeping at night (when it is dark) and being awake during the day (when it is light). The body's internal clock promotes sleepiness at certain times (e.g., late evening) and wakefulness at others (e.g., after a night's sleep). For the example of body temperature regulation: Body temperature typically follows a circadian pattern. It is lowest in the early morning (around 4 - 6 am) and highest in the late afternoon or early evening (around 4 - 6 pm).

Answer:

Circadian rhythms are internal biological processes with a ~24 - hour cycle. Examples: sleep - wake cycle, body temperature regulation.