Food Web Builder — Create and Explore Food Webs Online
A food web maps the feeding relationships between organisms in an ecosystem — who eats whom. Unlike a simple food chain (a single linear sequence), a food web shows the complex network of interconnected chains, reflecting how most organisms eat multiple things and are eaten by multiple predators. The food web builder on PublicSoftTools lets you add organisms, define feeding relationships, and visualise energy flow through any ecosystem.
Trophic Levels
| Trophic level | Type of organism | Energy source | Examples |
|---|---|---|---|
| Level 1: Producers (Autotrophs) | Plants, algae, phytoplankton, cyanobacteria | Photosynthesis (light) or chemosynthesis | Grass, oak trees, seaweed, wheat, pond algae |
| Level 2: Primary consumers (Herbivores) | Animals that eat only producers | ~10% of producer energy captured | Rabbits, caterpillars, deer, zooplankton, aphids |
| Level 3: Secondary consumers (Carnivores/omnivores) | Animals that eat primary consumers | ~10% of primary consumer energy | Foxes, ladybirds (eat aphids), small fish, frogs |
| Level 4: Tertiary consumers | Animals that eat secondary consumers | ~10% of secondary consumer energy | Eagles, sharks, killer whales, large predatory fish |
| Apex predators | Top predators with no natural predators | Top of the chain | Orca, polar bear, tiger, great white shark |
| Decomposers / detritivores | Break down dead organic matter | Dead organisms at any trophic level | Bacteria, fungi, earthworms, woodlice, dung beetles |
How to Use the Food Web Builder
- Open the food web builder.
- Add organisms using the Add organism button. Categorise each as producer, primary consumer, secondary consumer, tertiary consumer, or decomposer.
- Draw arrows between organisms to show "is eaten by" relationships. Arrows point from prey to predator (or from producer to consumer).
- The tool automatically calculates trophic levels and visualises energy flow.
- Use the energy pyramid view to see how energy decreases at each trophic level.
- Delete organisms to simulate extinction events and see how the web is affected (cascade effects).
Food Chain Examples Across Ecosystems
| Ecosystem | Food chain | Trophic levels | Notes |
|---|---|---|---|
| UK woodland | Oak leaves → Caterpillar → Blue tit → Sparrowhawk | 4 trophic levels | Classic British woodland food chain; sparrowhawks are apex predators in this chain |
| Ocean (pelagic) | Phytoplankton → Zooplankton → Herring → Tuna → Orca | 5 trophic levels | Marine chain; tuna at level 4; orca apex predator |
| Grassland (savanna) | Grass → Wildebeest → Lion | 3 trophic levels | Simple savanna chain; lions are apex predators |
| Freshwater pond | Algae → Water flea (Daphnia) → Small fish → Pike | 4 trophic levels | UK pond ecosystem; pike are apex freshwater predators |
| Arctic tundra | Lichen → Lemming → Arctic fox → Polar bear | 4 trophic levels | Arctic food chain; highly seasonally variable |
The 10% Energy Rule
When energy passes from one trophic level to the next, approximately 90% is lost — used by the organism for respiration, movement, heat production, and non-digestible material (waste). Only around 10% of the energy stored in biomass at one level is transferred to the next level. This is the 10% rule (also called the Lindeman efficiency).
Consequences:
- A grassland supporting 10,000 kg of grass can support approximately 1,000 kg of herbivores and 100 kg of primary carnivores
- Food chains are rarely more than 4–5 links long — not enough energy remains at higher levels to support populations
- Eating lower on the food chain is more energy-efficient — humans eating plant food require ~10× less land than humans eating meat from animals fed on plants
Food Webs vs. Food Chains
A food chain shows a single linear pathway: A → B → C → D. A food web shows the full network of feeding relationships:
- Most animals eat multiple prey species
- Most animals are prey for multiple predators
- Seasonal changes shift feeding patterns
- Omnivores appear at multiple trophic levels
Food chains are useful for teaching and illustrating specific pathways. Food webs are more realistic but also more complex — they show that removing one species rarely eliminates a predator because alternative prey exists. However, removing a keystone species (one with disproportionate influence) can destabilise the whole web.
Keystone Species
A keystone species has a disproportionately large effect on its ecosystem relative to its biomass. Removing a keystone species causes cascading changes throughout the food web — trophic cascade:
- Sea otters: Eat sea urchins. Without otters, urchin populations explode and overgraze kelp forests, eliminating habitat for hundreds of other species.
- Wolves in Yellowstone: Reintroduced in 1995. Their predation changed elk behaviour (less grazing near rivers), allowing vegetation recovery, which altered river courses — a "trophic cascade to geomorphology."
- Bees: Pollinate flowering plants. Removing bees would eliminate most flowering plants, collapsing ecosystems dependent on them.
Decomposers and Nutrient Cycling
Decomposers (bacteria, fungi) and detritivores (earthworms, woodlice, dung beetles) break down dead organic material from all trophic levels. They are not part of the main energy transfer pathway but are essential to ecosystem function:
- Release nutrients (nitrogen, phosphorus, carbon) back into the soil and atmosphere
- Make nutrients available for producers (plants) to absorb
- Without decomposers, nutrients would be locked in dead organic matter and producers would run out of minerals
The carbon cycle and nitrogen cycle both depend critically on decomposition. Decomposers are sometimes drawn at the base of the food web (receiving input from all levels) or as a separate parallel pathway.
Common Questions
What is the difference between a producer, consumer, and decomposer?
Producers (autotrophs) make their own food from inorganic substances using energy from sunlight (photosynthesis) or chemical reactions (chemosynthesis). Consumers (heterotrophs) cannot make their own food — they obtain energy by eating other organisms. Decomposers are a special type of consumer that break down dead organisms and waste, recycling nutrients back to the environment.
Can an organism be in more than one trophic level?
Yes — omnivores (bears, humans, pigs, badgers) eat both producers and consumers, placing them at multiple trophic levels simultaneously depending on what they eat. This is why food webs (not food chains) better represent reality. Trophic level can also be expressed as a fractional value when averaging across a varied diet.
What happens when an apex predator is removed?
Removing an apex predator causes a trophic cascade. Without the top predator controlling prey populations, the prey (often herbivores) increase in number, increasing grazing pressure on producers. This can lead to vegetation loss, soil erosion, and collapse of habitat that supports many other species. The reintroduction of wolves to Yellowstone is the most studied example of the positive effects of restoring apex predators.
Build a Food Web
Add organisms and define feeding relationships to build and visualise food webs — with energy pyramid and cascade effects.
Open Food Web Builder