Food Web Builder — Drag and Drop Ecosystem Tool
Build ecosystem food webs by adding organisms at different trophic levels and drawing predator-prey connections. A preloaded example shows a woodland ecosystem — reset, modify, or clear it to create your own. No signup, runs entirely in your browser.
Connect mode: Click the predator first, then its prey — the arrow shows what eats what. Use Move to drag nodes. Click arrows in Delete mode to remove connections.
How to Use the Food Web Builder
- 1Add organisms and place them at the right trophic level — producers at the base, consumers above.
- 2Switch to Connect mode, click the predator, then click its prey to draw a feeding arrow.
- 3Build up the network — most organisms have several food sources and several predators.
- 4Start from the preloaded woodland web, or clear it and design your own ecosystem.
Worked Example: The 10% Rule Across a Grassland Chain
Build a simple chain: grass → grasshopper → frog → snake. Suppose the grass captures 10,000 kJ of energy from sunlight per square meter. Only about 10% transfers at each step, because the rest is lost as heat through respiration and in undigested matter. So the grasshoppers hold roughly 1,000 kJ, the frogs about 100 kJ, and the snake just 10 kJ — a thousandth of where the chain started.
That steep drop is why the builder's trophic levels form a pyramid and why food chains rarely exceed four or five links: there simply isn't enough energy left to support another level of predators. It also explains biomagnification — a fat-soluble toxin that doesn't break down gets concentrated tenfold at each step, so the snake carries a far higher dose than the grass ever held. Add more predators and prey to see how a real web cushions against the loss of any single species compared with a fragile linear chain.
Ecology Concepts
Energy pyramids
Each trophic level contains less energy than the one below it due to the 10% transfer rule. An energy pyramid visualises this: wide base (producers with most energy), narrowing toward apex predators. Biomass and population pyramids follow the same pattern in most ecosystems.
Trophic cascades
Removing a top predator causes its prey population to explode (mesopredator release), which decimates the prey's prey and so on through the web. Reintroducing wolves to Yellowstone in 1995 changed even river morphology by altering elk grazing behaviour.
Bioaccumulation
Toxins like DDT and mercury accumulate in organisms and become more concentrated at each trophic level (biomagnification). Apex predators receive the highest doses. This is why large fish like tuna accumulate more mercury than small fish like sardines.
Decomposer role
Decomposers (bacteria, fungi, detritivores) break down dead organic matter and return nutrients to the soil, completing the nutrient cycle. Without decomposers, nutrients would be locked in dead biomass and ecosystems would collapse.
Frequently Asked Questions
What is a food web?
A food web shows the network of feeding relationships between organisms in an ecosystem. Unlike a linear food chain, a food web captures the complexity of real ecosystems where most organisms have multiple food sources and predators.
What are trophic levels?
Trophic levels describe an organism's position in the energy flow. Level 1 (producers): plants and algae that photosynthesise. Level 2 (primary consumers): herbivores that eat producers. Level 3 (secondary consumers): carnivores that eat herbivores. Level 4 (tertiary consumers): apex predators. Decomposers break down dead organic matter at all levels.
How do I connect organisms?
Switch to Connect mode, click the predator first, then click the prey. An arrow is drawn from predator to prey showing the "eats" direction. This represents energy flow — arrows point from eaten to eater, or from prey to predator depending on convention; here arrows go from predator to prey to indicate what each organism eats.
How much energy is transferred between trophic levels?
Approximately 10% of energy is transferred from one trophic level to the next — the rest is lost as heat through respiration. This is why food chains rarely exceed 4–5 levels; there is not enough energy to support larger populations at higher levels.
What is a keystone species?
A keystone species has a disproportionately large impact on its ecosystem relative to its biomass. Removing one can trigger a trophic cascade — causing population explosions or collapses at multiple levels. Classic examples include sea otters, wolves, and sharks.
Is the data saved?
No. Your food web exists only in your browser session. Use screenshots or screen recording to save your diagrams.