Only a fraction of the energy stored at one trophic level is available to the next — most is lost as metabolic heat, movement and undigested matter (the "10% rule").
E(n+1) = E(n) × efficiency
Producers → primary consumers → secondary consumers → apex predators
- Trophic levels — how many tiers the pyramid has, from producers to apex predator.
- Transfer efficiency — the fraction of energy passed up each level; ~10% is typical in real ecosystems.
- Disturbance — removes the apex predator, letting you watch how the levels below cascade out of balance.
Real-world relevance: this energy loss is why food chains rarely exceed 4-5 levels, and why apex predators are always far rarer than the producers that ultimately feed them.