Food web builder sim
Pin arrows between pond organisms from the food to the feeder, label each organism's level (one can feed at two), then take a species out or put in a perch or a disease and step the seasons, predicting each population's rise or fall and reading why it changed.
Ecosystems: food webs, producers, consumers and decomposers, trophic levels, and interdependence · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Food web builder. A cork pinboard stands on the bench with 9 cards for the organisms of one pond, plus a box for dead matter and waste. Drag from one card to another to pin an arrow: an arrow points from the food to the feeder, the way energy moves. Producers (algae and pondweed) make their own food by photosynthesis; primary consumers eat producers; secondary consumers eat primary consumers, and so on. The decomposers, bacteria and fungi, feed on dead matter and waste and return mineral ions to the producers (a dashed arrow, because it carries matter, not energy). When the web is complete, label each organism's level: one organism can feed at more than one level. Then make one change: drag a card into the taken-out tray, put the perch card on the board, or put the disease token on an animal. Predict, then press Next season to see how each population changes through the links. A species with only one food in this web is hit hardest when that food falls; a species with several foods can switch to the others. Populations can overshoot and swing before settling. Real effects differ: in a real pond the sizes and timings would not match these, and other factors also act. Simplified on purpose: the population numbers are illustrative (≈): each is a percentage of that species' size at the start, worked out by a simple model and rounded to a whole per cent each season; a small web of nine kinds of organism in one pond; a real pond holds hundreds of kinds, so its web is far larger and more tangled; time moves in whole seasons, one click at a time; no migration: nothing flies or swims in or out, so a heron cannot find food at another pond; the same amount of light every season, and no weather; the model is deterministic: the same change always gives the same seasons; each feeder eats its foods in fixed shares at the start, and eats more of what is left when one food runs short; detritus feeders (animals such as some snails that also eat dead matter) are left out, so only bacteria and fungi break down dead matter; the decomposers stand for many kinds of bacteria and fungi together; the cards and pictures are not to scale; crowding pulls each population towards the size its food can support: births follow the food each individual gets, so a species with no food left in this web dies out; the two producers share one supply of mineral ions in the water, which the decomposers refill and the producers use up; light and space slow each producer's growth more and more above about 1.4 times its starting size, so with fewer grazers it can go higher; natural deaths, including being eaten by animals left out of this web, take a fixed share of each population every season; nothing in this web eats the perch, although in a real pond herons do take perch.
- Solid arrow: energy passes from the food to the feeder
- Dashed arrow: mineral ions returned by the decomposers (matter, not energy)
- Bar on a card: that population as a share of its starting size (the tick is 100%)
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
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