Food Web Builder — Create and Explore Ecosystem Energy Flow

Trophic Levels at a Glance

How to Use the Food Web Builder

1. Open the Food Web Builder
2. Click Add Organism, enter a name, and select its trophic level (Producer, Primary Consumer, etc.)
3. Switch to Connect mode, then click one organism and then another to draw a "eats" arrow between them
4. Drag organisms to rearrange the layout and reduce overlapping arrows
5. Switch to Delete mode and click a node or arrow to remove it
6. Use Clear to reset the canvas or explore the pre-loaded example ecosystem

Energy Flow and the 10% Rule

Energy flows through trophic levels, but most is lost at each transfer. The 10% rule states that only approximately 10% of energy is passed from one trophic level to the next — the remaining 90% is lost as heat, used for respiration, or goes to decomposers.

This explains why food chains rarely exceed 4–5 levels: by the fifth trophic level, less than 0.01% of the original producer energy remains. It also explains why eating lower on the food chain is more energy-efficient — a field of grass supports far more people than the same field converted to beef production.

Food Web Concepts

Keystone species

A keystone species has a disproportionately large effect on its ecosystem relative to its abundance. Sea otters are a classic example: they eat sea urchins, which eat kelp. Without otters, urchin populations explode and eliminate kelp forests, collapsing the entire ecosystem. Removing a keystone species can cause trophic cascade — a chain reaction of population changes across multiple levels.

Trophic cascade

Trophic cascades occur when changes at one trophic level ripple through others. The reintroduction of wolves to Yellowstone is a celebrated example: wolves reduced elk grazing pressure, allowing riverside vegetation to recover, which stabilised stream banks, changed water flow, and increased biodiversity — all from the addition of a single predator species.

Omnivores and complex webs

Many organisms feed at multiple trophic levels — bears eat salmon and berries; humans eat both plants and animals. Omnivores create loops in the food web that make them harder to model as simple chains. In the food web builder, an omnivore can receive arrows from both producer and consumer levels.

Decomposer loop

Decomposers (bacteria, fungi, detritivores) receive energy from dead organisms at all trophic levels. They break down organic matter into inorganic nutrients (nitrogen, phosphorus, carbon) that are recycled back to producers. Without decomposers, ecosystems would quickly become buried in dead matter and run out of the nutrients needed for primary production.

Common Questions

What is the difference between a food chain and a food web?

A food chain is a single linear sequence (grass → rabbit → fox → eagle). A food web is a network of overlapping food chains showing the full complexity of feeding relationships. In reality, most organisms eat multiple species and are eaten by multiple predators — a food web is always a more accurate representation than a food chain.

Why do invasive species disrupt food webs?

Invasive species enter an ecosystem without the predators, pathogens, and competitors that kept them in check in their native range. They can outcompete native species at their trophic level, prey on organisms that have no evolved defences, or introduce diseases. The cane toad in Australia and the brown tree snake in Guam are examples of invasives that dramatically restructured local food webs.