Food Web Builder

How to use it

Choose a boreal forest, a pond or an ocean (a kelp forest off the coast of British Columbia). In Build mode, tap a species that is eaten, then tap the species that eats it, to draw an arrow from food to eater. With a mouse you can also drag from the food to the eater. Tap an arrow to remove it, or open the list of arrows under the web. With a keyboard, Tab to a species, press Enter, then Tab to its eater and press Enter. Press Escape to cancel.

Check my web marks correct arrows in green and wrong ones in red, explains each mistake and counts how many are missing. Show the answer adds the missing arrows in blue. In Explore mode, tap a species to see what it eats and what eats it, then remove it to see who loses food, who could starve, and who might increase. The toggles add role colours, role labels and the 10% energy rule.

Food chains and food webs

A food chain is one path of energy, such as willow, snowshoe hare, lynx. A food web joins many chains, because most animals eat more than one thing and are eaten by more than one thing. Producers (plants, algae and phytoplankton) make their own food from sunlight. Primary consumers eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers. Decomposers such as fungi and bacteria break down dead remains and wastes from every level, returning nutrients to the soil or water.

The arrows point from the food to the eater because they show which way energy flows. Only about 10% of the energy at one level passes up to the next, so there are always far fewer predators than plants. Many animals eat at more than one level, so the rows here are a simplification.

When a species disappears, its predators lose food. If it was their only food, they starve or move away, and that knocks on to whatever ate them. Its prey can increase, and then eat more of their own food. Remove the sea otter in the ocean web to see a famous example: more urchins, less kelp.

• Follow one food chain from a producer to the top. How many links does it have?
• Which species, if removed, affects the most others? Why?
• Why are there fewer wolves than snowshoe hares in a forest?
• What would happen to a pond with no decomposers?

Free to use, no account needed. It runs in your browser: nothing you type, and no sound from your microphone, is sent to Fieldbook.