Food Web Dynamics

Explore energy flow and trophic levels in an ecosystem

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.