What term describes cyclic phenomena that occur with established regularity in living organisms?

The term that describes cyclic phenomena occurring with established regularity in living organisms is "biorhythms." Biorhythms are natural cycles that regulate various biological processes and functions within organisms. These cycles can be daily, monthly, or yearly and include changes in physiological states such as sleep-wake cycles, hormone levels, and other metabolic processes that happen at predictable times.

Understanding biorhythms can be crucial in fields such as medicine, psychology, and biology, as disruptions in these cycles can lead to health issues or affect overall well-being. In contrast, other options refer to specific medical conditions or terms rather than cyclical biological phenomena. Botulism is a rare illness caused by a toxin from bacteria, bradycardia refers to an abnormally slow heart rate, and bronchiectasis is a lung condition characterized by the abnormal dilation of the bronchi. None of these terms relate to the concept of cyclic biological rhythms.