Food Chains and Food Webs: Two Wren and Sitka Nature Lessons, Grades 3-5

A food chain is a way of drawing where energy goes. The arrows point in the direction the energy travels, which trips people up. The arrow goes from the eaten to the eater.

It starts with producers. Plants make their own food from sunlight, so nothing had to be eaten for them to live.

Then come consumers. A plant eater is a herbivore. A meat eater is a carnivore. An animal that eats both is an omnivore.

At the end come decomposers. Fungi, bacteria, and some insects break down what is left and return it to the soil, where plants use it again.

Energy is lost at every step, mostly as heat. That is why there are always far more plants than plant eaters, and far more plant eaters than predators.

Real animals have options. A fox eats mice, but also berries, birds, eggs, and beetles. Draw every one of those arrows and the neat chain becomes a tangle.

That tangle is a food web, and it is the honest picture. Most animals appear in several chains at the same time.

Webs matter because they explain what happens when something goes wrong. If one food disappears, an animal with many options shifts to another. An animal with only one option is in trouble.

Scientists call a species that holds a whole web together a keystone species. Remove it and far more collapses than you would expect from one animal.