PRODUCERS AND CONSUMERS
FOOD PYRAMIDS
On the left is a food pyramid.
It shows how consumers can get larger in size, but smaller in number, as you go along the food chain.
When a moth caterpillar eats a leaf it uses up some of the energy from the leaf for itself.
So there is less to pass on to a robin. That means the robin needs to eat several moth caterpillars to get enough energy. So there are fewer robins than caterpillars.