The population of each organism in a food chain can be shown in a type of bar chart called a pyramid of numbers. The bars are drawn to scale – the more organisms it represents, the wider the bar. The producer in the food chain always goes at the bottom of the pyramid of numbers.
Think about this food chain:
clover → snail → thrush → hawk
Clover is a plant and it is the producer in this food chain. Its bar goes at the bottom of the pyramid:
Energy is lost to the surroundings as we go from one level to the next, so there are usually fewer organisms at each level in this food chain. A lot of clover is needed to support the snail population. A thrush eats lots of snails, and a hawk eats lots of thrushes, so the population of hawks is very small.
Sometimes the pyramid of numbers does not look like a pyramid at all. This could happen if the producer is a large plant such as a tree, or if one of the animals is very small. Remember that the producer always goes at the bottom of the pyramid.
Here are two examples of this: