A biological cycle, or rhythm, that is approximately 25 hours long is called

Answer: Circadian Rhythms

There are three types of biological rhythms.

→The one that occurs about every day (approx 24 hours) is known as Circadian Rhythms. For example, Hormone secretion, urine production, sleep etc.

→The one that occurs after more than a day like menstrual cycles of women (28 days) is known as Infradian Rhythms.

→The one that occurs more than once a day is known as Ultradian Rhythms like sleep, hormone levels etc.

Therefore, a biological cycle that is approximately 25 hours long is called Circadian Rhythms.