Food Web Dynamics
Explore energy flow and trophic levels in an ecosystem
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How it works
A food web shows all the feeding relationships in an ecosystem — who eats whom. Energy enters the web through producers (plants, algae) that capture sunlight via photosynthesis. Primary consumers (herbivores) eat producers, secondary consumers eat herbivores, and tertiary consumers (top predators) eat other consumers. At each step, roughly 90% of energy is lost as heat through cellular respiration, leaving only about 10% for the next level. This is the 10% rule, and it explains why ecosystems have many more plants than herbivores, and far more herbivores than top predators. When a species is removed, the effects cascade through the web. Removing wolves from Yellowstone caused elk populations to explode, which overgrazed riverside vegetation, which eroded stream banks — a trophic cascade. Food webs with more connections (higher biodiversity) are more resilient because organisms have alternative food sources.
Step-by-step
- Choose a scenario — Wolves in Yellowstone, Invasive Species, or Kelp Forest (sea otters) — and watch the food web react.
- Drag the predator and prey population sliders to see how a keystone species' numbers ripple through every level: remove the predators entirely (slider to 0) and watch the prey explode, then overgraze.
Key formulas
- Energy available at the next trophic level depends on transfer efficiency (typically ~10%)
- Biomass decreases at higher trophic levels because energy is lost as heat at each step
Frequently asked questions
- If a grassland receives 10,000 kJ of sunlight energy, and plants capture 1% of it, how much energy is available to herbivores? To secondary consumers?
- Plants capture 1% of 10,000 kJ = 100 kJ. With 10% transfer efficiency, herbivores get 100 × 0.10 = 10 kJ. Secondary consumers get 10 × 0.10 = 1 kJ. This dramatic drop explains why top predators need huge territories — there simply is not much energy left for them.
- A forest ecosystem has hawks, snakes, mice, grasshoppers, and grass. Draw the food chain. If grasshoppers are wiped out by disease, what happens to the rest?
- Chain: grass → grasshoppers → mice → snakes → hawks. Without grasshoppers, mice lose a competitor for grass — mice population may increase. More mice means more food for snakes, so snake population may rise. But it depends on whether mice also eat grasshoppers. In a web (not just a chain), effects are more complex because species have multiple food sources.