Biological Clock
Biological Clock is the inner system that tells an animal when to sleep, wake, and eat.
A slow-drip jar sits on a counter and fills at a steady rate all day. When the water hits a low mark, a float opens a valve — time to eat. When it hits a high mark, the float shuts the valve — time to rest. An animal's body has the same kind of inner timer that sends signals to wake, eat, or sleep.
Explaining biological clock by grade level
A hamster runs on its wheel at the same time each night. If you change when the lights go on and off, it gets mixed up. For a few days, it runs at odd times. Then it shifts and starts on a new pattern that fits the new light.
Projects that explore biological clock
Hamsters are active at predictable times each day, but disrupting their light cycle shows just how much that steady rhythm depends on the inner system controlling it. You split ten hamsters into two groups and track their time on exercise wheels. After two days on the same schedule, one group gets a sudden shift in their light-dark cycle while the other stays on the original. As a result, the shifted hamsters drop from about 150 minutes of wheel time to under 40 minutes, and it takes roughly a week before they return to normal activity levels.
Social companionship can influence how quickly an animal's inner clock adjusts after a disruption. Every animal has a biological clock — an internal timer that follows day-night cycles — and disrupting that cycle changes behavior. You house six hamsters in four cages: two cages hold single hamsters and two hold pairs. All follow a 12-hours-on, 12-hours-off light schedule for five days, then you shift the schedule by one hour for half the cages. Tracking exercise wheel use over the next five days shows that paired hamsters adapted to the new schedule more quickly, while solo hamsters took longer to return to normal activity levels.
An animal's inner clock can tell it when to eat. Many animals follow patterns in their daily behavior. You can feed fish at the same time each day. Then switch the time and watch how long the fish takes to adjust.