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.
Unlock Food Web Dynamics
Plus 148+ other Pro labs covering AP Physics, Biology, Chemistry, Earth Science, and Math — with unlimited simulation time, advanced parameters, and detailed analytics.
Already have an account?
Sign in →What is Food Web Dynamics?
A food web is a diagram of who eats whom in an ecosystem. Unlike a simple food chain with a single path, a real food web shows all the overlapping feeding relationships — most animals eat more than one thing, and most organisms are eaten by more than one predator. Energy enters the web through producers: plants and algae that capture sunlight via photosynthesis. Primary consumers (herbivores) eat the producers, secondary consumers eat the herbivores, and so on up to top predators. At each step, roughly 90% of the energy is lost as heat, which is why most simplified food webs show more producer biomass and far fewer top predators than lower-level consumers. This energy loss creates the biomass pyramid: a wide base of producers supporting progressively fewer and fewer animals at higher levels. The simulation lets you choose different ecosystem types, experiment with different energy transfer rates, and remove species to trigger trophic cascades — chain reactions that ripple through every level of the web when one species disappears.
Parameters explained
- Predator Population
- Predator Population sets how many predators begin the simulation, from none to a dense predator group. A low value lets prey grow with little hunting pressure, while a high value can push the system toward prey decline and possible predator collapse later if food becomes scarce. Use this slider after selecting a preset to test whether the same food web is stable under different starting conditions. In the Yellowstone and kelp examples, changing predators helps students connect keystone species to population balance without treating predators as simply good or bad.
- Prey Population
- Prey Population sets the starting number of prey organisms available to support predators, from a small prey base to a crowded prey population. Raising prey can temporarily support more predators, but it may also show how rapid prey growth changes the balance reading before predators respond. Lowering prey makes food limitation visible: predators may not have enough energy intake to remain stable over time. Compare this slider across the Wolves in Yellowstone, Invasive Species, and Kelp Forest presets to separate the effect of web structure from the effect of starting population size.
Common misconceptions
MisconceptionRemoving one species from a food web only affects the species that ate it.
CorrectA change in one species can trigger a trophic cascade — effects ripple both up and down the web. A predator increase, prey crash, invasive species, or keystone-species loss can change food availability for several connected organisms. In real ecosystems these effects sometimes travel through four or five trophic levels before stabilizing.
MisconceptionThe 10% rule means exactly one-tenth of the energy transfers perfectly at every step.
CorrectTen percent is a useful approximation that varies in real ecosystems — it can range from about 5% to 20% depending on the organisms and environment involved. The key concept is that energy is always lost at each step, not that the fraction is precisely 10% in every case.
MisconceptionTop predators are the most important species in a food web because they are at the top.
CorrectAll levels are important, and in many ways producers are the most critical because they are the only source of new energy in the system. Removing producers collapses the entire web. Top predators often have an outsized effect on ecosystem structure (keystone predator effect), but a food web cannot exist without its producer base, no matter how many predators are present.
MisconceptionOcean food webs work differently from land food webs.
CorrectThe same fundamental principles apply in all ecosystems: energy flows from producers to consumers, only a fraction transfers at each step, and population changes can trigger cascades. The specific organisms differ — phytoplankton replace grasses, zooplankton replace insects — but the structural rules are similar. This is why ecologists can apply related models across very different biomes.
How teachers use this lab
- Start with the Wolves in Yellowstone preset, set Predator Population to 10 and Prey Population to 100, and have students describe the visible connections before pressing Play.
- Keep the Yellowstone preset active, lower Predator Population to 0, and ask students to predict how reduced hunting pressure could affect prey and vegetation in a real trophic cascade.
- Use the Invasive Species preset to discuss competition: students identify which organisms may gain or lose resources, then test different Prey Population values and record the balance status.
- Use the Kelp Forest preset as a keystone-species case study. Students compare low and high Predator Population settings and explain how otters can indirectly protect kelp by limiting urchins.
- Run a three-preset comparison activity where groups keep both sliders unchanged, switch between Yellowstone, Invasive Species, and Kelp Forest, and argue how web structure changes ecosystem resilience.
Frequently asked questions
What is the difference between a food chain and a food web?
A food chain is a single linear sequence of who eats whom — grass to grasshopper to frog to snake to hawk. A food web shows all the interconnected feeding relationships in an ecosystem at once. Most real organisms eat multiple food sources and have multiple predators, so a food web is a much more accurate representation of how energy actually flows through an ecosystem. Food chains are simpler and easier to analyze mathematically, which is why they appear in textbooks, but food webs are closer to ecological reality.
Why do ecosystems with more biodiversity tend to be more stable?
Higher biodiversity means more species at each trophic level and more connections in the food web. If one species disappears, other species can often fill its role — predators have alternative prey, and herbivores have alternative plants to eat. A food web with few species and few connections is more fragile: losing one species can disconnect large parts of the web. This is why conservation biologists often focus on protecting entire ecosystems and their biodiversity rather than single species in isolation.
Which NGSS standards does this experiment address?
This simulation supports MS-LS2-3 (develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem) and MS-LS2-4 (construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations). The predator and prey sliders model population interactions, while the presets provide ecosystem cases for comparing energy flow, keystone species, invasive species, and cascade effects.
How does energy transfer efficiency affect the number of trophic levels?
With about 10% efficiency, energy drops by a factor of 10 at each level. Starting with 10,000 kJ in producers, herbivores get roughly 1,000 kJ, secondary consumers get 100 kJ, and tertiary consumers get only 10 kJ. By four or five levels, there often is not enough energy left to support a breeding population of top predators. This is why food webs usually have broad producer and prey bases supporting smaller predator populations.
What is a keystone species?
A keystone species has a disproportionately large effect on its ecosystem relative to its abundance — like a keystone in an arch that holds the whole structure together. Sea otters are a classic example: they eat sea urchins, which eat kelp. Without otters, urchins multiply and demolish kelp forests, destroying habitat for hundreds of other species. Use the Kelp Forest preset and predator slider to explore how predator abundance can indirectly protect or destabilize other parts of the web.