Reading Food Web Diagrams

You have followed food chains from food to eater. A food web connects several chains. Each arrow points from food to its eater. Our pond model has four feeding arrows. Each box below shows one separate link, not a chain of boxes.

Pondweed makes its own food, so it is the producer. The snail eats only pondweed: it is a herbivore and primary consumer. The fish and heron eat only animals here, so they are carnivores. To find food for an animal, find an arrow ending at it and read back to the source.

To trace a chain, follow arrows from a producer to each eater. At a fork, try another route. Here the routes are Pondweed → Snail → Fish → Heron and Pondweed → Snail → Heron. To find shared species, compare both complete lists. Pondweed, snail and heron appear in both; fish appears in only one.

If snails disappear, fish lose their only food in this model, so fish numbers could fall. Another snail-eating predator could increase hunting of snails. Food supply, disease and links omitted from real-world diagrams also matter. Check all links, but describe possible changes rather than certain numbers.

For feeding roles, find the producer that makes food. An animal eating it is a primary consumer. An animal eating that consumer is a secondary consumer. A decomposer, such as a fungus, breaks down dead material. In a diagram, an arrow from dead material to a decomposer shows food reaching it; the dead material is not a producer.