Food webs — Science, 11–13
Living things in an ecosystem are linked by who eats whom. Food webs show that one species can depend on several others, not just one straight chain.
Many chains are joined
A food chain might show grass, rabbit and fox, but a real habitat is more tangled. A rabbit may eat several plants and be eaten by foxes, owls or people. Joining these chains creates a food web, where arrows show the direction of food energy: from the eaten organism to the eater.
Why use a web?
The problem with a single food chain is that it can make nature look like a neat line. If one food source disappears, an animal may switch to another, but its predators may still be affected. A food web helps us reason about these connected changes instead of guessing from one link.
When grass declines
Imagine a meadow web: grass feeds rabbits and grasshoppers; rabbits feed foxes; grasshoppers feed frogs; frogs feed herons. A dry summer reduces the grass. Rabbits and grasshoppers now have less food, so their numbers may fall. Foxes, frogs and herons may later have less prey, although each could be affected differently by other available foods.
Arrows point to the eater
A common mistake is drawing the arrow from the predator to its prey, because we often say that a fox hunts a rabbit. In a food web, the arrow means “energy moves to”, not “chases”. It points from the food to the eater: grass → rabbit → fox. Reading the arrow’s meaning prevents reversed conclusions.
Protecting habitats
Ecologists use food webs when planning wildlife reserves, restoring rivers or deciding how to control an invasive species. Removing one organism can affect many others, while protecting a plant may support insects, birds and mammals. The web is a guide to connections, not a promise that every change has one predictable result.
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