Question

A biological cycle, or rhythm, that is approximately 24 hours long is called a(n) ________ cycle.

A. ultradian

B. diurnal

C. infradian

D. circadian

Answer 1

Answer: D. circadian

Explanation: What are circadian rhythms? Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark and affect most living things, including animals, plants, and microbes.

Answer 2

A biological cycle that lasts about 24 hours is called a circadian cycle, which is regulated by an internal biological clock and includes physiological processes like the sleep-wake cycle.

Step-by-step explanation:

A biological cycle, or rhythm, that is approximately 24 hours long is called a circadian cycle. These are internal rhythms of biological activity that repeat on a roughly 24-hour schedule, manifesting in various physiological processes and behaviors. For example, our sleep-wake cycle, heart rate, and body temperature all follow a circadian rhythm closely linked with the light-dark cycle of our environment. Circadian rhythms are regulated by a biological clock found in the brain, and despite external conditions, these natural cycles persist, demonstrating their innate nature.