Food chains, energy pyramids and the carbon cycle
BiologyEcology & EnvironmentAges 17–18
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Ecology & Environment
Solar energy fixed by producers is passed along a food chain through successive trophic levels; at each level most energy is lost as respiration, heat and waste, and only about 10% moves up to the next level, which is why an energy pyramid always has a wide base. Students can change the number of trophic levels, the ecological efficiency and the food chain (grassland or pond), click each level to see energy received, lost and transferred, and watch carbon cycle through photosynthesis, consumption, decomposition, respiration and fossil-fuel combustion. A Pyramid types tab compares pyramids of numbers, biomass and energy in a grassland, an oak tree and the open sea, including inverted pyramids.
Lesson: Ecosystems: food chains, energy flow, ecological efficiency, pyramids of numbers, biomass and energy; biogeochemical cycles (carbon)
What it shows
Energy enters most ecosystems as sunlight captured by producers and passes up a food chain as organisms are eaten. At each trophic level most of it is used in respiration or lost as heat and waste, so only about 10% reaches the next level, which limits food chains to four or five levels. Carbon, by contrast, is recycled. The Pyramid types tab compares pyramids of numbers, biomass and energy: one oak tree feeding thousands of caterpillars gives an inverted pyramid of numbers, the open sea an inverted pyramid of biomass, but a pyramid of energy is never inverted.
How to use
On Energy and carbon, pick a food chain with the Chain button, set the Efficiency and Levels sliders and click a level to read the energy received, lost and passed on; turn on Carbon cycle to trace carbon. On Pyramid types, choose an Ecosystem and a Pyramid of type, switch Bar widths to Log scale to see small levels, and press Upright or Inverted to record each shape.
Parameters you can change
- Number of trophic levels 3–5
- Ecological efficiency between levels 5–20 %
- Energy fixed by producers 1000–1000000 kcal/m²/yr
- Food chain Grassland: grass → grasshopper → frog → snake → hawk, Pond: algae → crustacean → small fish → large fish → kingfisher
- Show carbon cycle
- View Energy and carbon, Pyramid types
- Ecosystem Grassland, One oak tree, Open sea
- Pyramid of Numbers, Biomass, Energy
- Bar widths To scale, Log scale
Questions to explore
- With 10% ecological efficiency, what fraction of the producers' energy reaches the fifth trophic level?
- Why can a pyramid of energy never be inverted?
- How does burning fossil fuels change the balance of the carbon cycle?
