Final answer:
An environmental event that resets a biological rhythm, such as the circadian rhythm, is called a zeitgeber. Light and temperature are examples of zeitgebers that can synchronize the body's internal cycles with the external environment.
Step-by-step explanation:
An environmental event that resets a biological rhythm is known as a zeitgeber. Biological rhythms are internal cycles of biological activities, such as the circadian rhythm, which is a cycle that takes around 24 hours to complete and affects various physiological processes like sleep-wake cycles, body temperature, and hormonal changes. Environmental cues, such as changes in light or temperature, act as zeitgebers that can reset these biological clocks, aligning the body's internal processes with the external environment.
For example, exposure to natural light in the morning can help reset our circadian rhythms, which may be disrupted during travel across time zones or shift work. The biological clock, located in a gland at the base of the brain, reacts to these environmental cues. It adjusts the body's cycles to be in sync with the 'new' light-dark cycle or temperature changes, thus maintaining or restoring a healthy balance in our physiological functions. This mechanism is vital for optimal health and well-being.