Energy Dynamics & Food Web Lab
Investigate how energy moves through ecosystems by manipulating food webs and tracking energy at every trophic level. Remove species to trigger trophic cascades, compare ecosystem types, and collect data to verify the 10% rule experimentally.
Guided Experiment: The 10% Rule Investigation
What fraction of energy do you predict will be transferred from one trophic level to the next? How much energy will reach the top predator?
Write your hypothesis in the Lab Report panel, then click Next.
Food Web Diagram
Arrow width is proportional to energy transferred. Node size is proportional to energy.
Controls
Energy Analysis
where k = number of predators competing for the same prey
Energy by Trophic Level
Energy Budgets
| Species | Energy In | Respiration | Growth | Waste |
|---|---|---|---|---|
| Grass | 6666.7 | 3333.3 | 2333.3 | 1000.0 |
| Wildflowers | 3333.3 | 1666.7 | 1166.7 | 500.0 |
| Grasshopper | 222.2 | 133.3 | 22.2 | 66.7 |
| Rabbit | 388.9 | 233.3 | 38.9 | 116.7 |
| Mouse | 388.9 | 233.3 | 38.9 | 116.7 |
| Frog | 26.7 | 16.0 | 2.7 | 8.0 |
| Snake | 51.9 | 31.1 | 5.2 | 15.6 |
| Hawk | 26.0 | 15.6 | 2.6 | 7.8 |
Data Table
(0 rows)| # | Time Step | Producers(kcal/m²/yr) | Primary Consumers(kcal/m²/yr) | Secondary Consumers(kcal/m²/yr) | Tertiary Consumers(kcal/m²/yr) | Transfer Eff.(%) |
|---|
Reference Guide
Trophic Levels
Every organism in an ecosystem belongs to a trophic level based on its position in the food chain. Producers (plants) form the base, followed by primary consumers (herbivores), secondary consumers (small predators), and tertiary consumers (top predators).
Each level typically receives only 10% of the energy from the level below. This limits food chains to 4-5 levels.
Energy Transfer and Budgets
When energy passes from prey to predator, most is lost. A typical consumer uses about 60% of ingested energy for respiration (heat), 30% is excreted as waste, and only 10% becomes new biomass (growth).
R = respiration, G = growth (new biomass), W = waste. Only the growth component is available for the next trophic level.
Trophic Cascades
Removing a species from a food web can trigger a trophic cascade, where effects ripple through the ecosystem. If a top predator is removed, its prey populations can explode (mesopredator release), depleting species at lower levels.
The classic example is Yellowstone, where reintroducing wolves reduced elk overgrazing, allowing riverbank vegetation to recover and reducing stream erosion.
Top-down control means predators regulate prey populations. Bottom-up control means producer availability limits consumer populations.
Food Web Stability
Food webs are more resilient than simple food chains because they offer multiple pathways for energy flow. If one species declines, predators can switch to alternative prey.
A keystone species has a disproportionately large effect on its ecosystem relative to its abundance. Removing a keystone species can collapse the food web, while other species can be removed with minimal impact.
Higher connectance (the fraction of possible links that actually exist) generally increases food web stability up to a point.