A meadow has grass, rabbits, and foxes. Today we will change the meadow — and you will predict what happens before we run each experiment.
Before we start — picture a field of grass, rabbits, and foxes — what do you think each one needs to stay alive?
Each level is eaten by the level above it. There is lots of grass, fewer rabbits, and only a few foxes — that is why a food chain is shaped like a pyramid.
Each population grows when it has enough food, and shrinks when something eats it. When a population grows and shrinks at the same speed, its numbers stay steady — that is balance.
No foxes meant too many rabbits — until the grass ran out and the rabbits went hungry. The foxes were protecting the grass all along.
The drought never touched a single fox. But less grass meant fewer rabbits — and fewer rabbits meant hungry foxes.
When extra foxes arrived there wasn't enough food for all of them. Within two years, the meadow had pulled itself back to balance.