What are rhythms synchronized to environmental cues called?

Rhythms synchronized to environmental cues are called circadian rhythms.

Imagine you're a little plant that lives on your windowsill. Every day, it gets brighter outside, that's sunlight, and every night, it gets darker, that's darkness. The plant knows when to wake up and when to rest because of these changes in light. That’s kind of like how you know when to go to bed or when to get up, your body uses clues from the world around you.

Your body has a kind of internal clock, just like the plant has its own way of telling time. This internal clock helps your body know when it's time to be active and when it's time to rest. Scientists call this kind of rhythm circadian rhythms, "circa" means around, and "dian" means day.

When you see the sun rise, that’s a clue (or cue) telling your body it's time to wake up. When the sun sets, that’s another cue saying it's time for sleep. Just like how the plant uses sunlight to know what to do next!