Final answer:
Melatonin, produced by the pineal gland, is responsible for regulating the sleep-wake cycle and other circadian rhythms, adjusting physiological processes according to the day-night pattern.
Step-by-step explanation:
The hormone responsible for daily changes in physiological processes that follow a day-night pattern is melatonin. Melatonin is secreted by the pineal gland and plays a crucial role in regulating the sleep-wake cycle and other circadian rhythms. Its secretion is stimulated by darkness and inhibited by bright light, aligning our biological clocks with the natural day-night cycle.