Scivra
Pro 🔒~15 min

Food Web Dynamics

Explore energy flow and trophic levels in an ecosystem

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.

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Step-by-step

  1. Select an ecosystem to explore its food web.
  2. Watch energy flow from the sun through producers to top predators — the width of each arrow shows how much energy transfers.
  3. Use the species removal slider to see what happens when you take out a top predator, mid-level consumer, or producer.
  4. Adjust energy transfer efficiency to see how it changes the biomass pyramid.

Key formulas

  • En+1=En×efficiency100(energy transfer between levels)E_{n+1} = E_n \times \frac{\text{efficiency}}{100} \quad \text{(energy transfer between levels)}Energy available at the next trophic level depends on transfer efficiency (typically ~10%)
  • Biomass pyramid: Bproducers>Bprimary>Bsecondary>Btertiary\text{Biomass pyramid: } B_{\text{producers}} > B_{\text{primary}} > B_{\text{secondary}} > B_{\text{tertiary}}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.