Nitrogen cycle sim
Drag a nitrogen atom counter round a model board, step by step, naming what moves it (nitrogen-fixing, nitrifying and denitrifying bacteria, decomposers, lightning, roots, feeding, death and waste), then test a drained and a waterlogged soil tank week by week for ammonium and nitrate.
Ecosystems: the nitrogen cycle and the roles of nitrogen-fixing, nitrifying and denitrifying bacteria and decomposers · covers the IGCSE topic
What the sim shows
Nitrogen cycle. A magnetic model board stands on the bench with 6 station tiles: nitrogen gas in the air, nitrate ions and ammonium ions in the soil, protein in plants, protein in animals, and dead matter and waste. Drag the nitrogen atom counter along one step of the cycle, then choose what makes that step happen. Nitrogen-fixing bacteria (some in the root nodules of legumes) and lightning fix nitrogen gas. Plants absorb nitrate ions through their roots and make amino acids and proteins; animals get nitrogen only by eating protein. Death, faeces and urine (urea from deamination) pass nitrogen to the dead matter, where decomposers (bacteria and fungi) release ammonium ions. Nitrifying bacteria turn ammonium into nitrate (they need oxygen), and denitrifying bacteria turn nitrate back into nitrogen gas (fastest in waterlogged soil). At the front, a soil tank with dead leaves dug in shows the bacteria at work: put the drain bung in to keep it waterlogged, or leave it out so it drains, then step one week at a time and test the soil for ammonium and nitrate. Simplified on purpose: one nitrogen atom stands for the many atoms that take each route at once; real nitrogen moves along all the routes all the time; six stations only: nitrite is mentioned inside nitrification but has no tile, and amino acids and urea are mentioned inside the steps; plants take up nitrogen only as nitrate ions on this board, although real plants also take in some ammonium ions; animals that eat other animals are left out, so animal protein comes only from plants here; the soil amounts are illustrative (≈): a simple model with one fixed rate for each step in each kind of soil, read to the nearest whole mg per kg; the tank has no plants, so no nitrate is taken up by roots in part 2; the soil is either fully drained or fully waterlogged, and stays that way for the whole run; real fields change with the weather; the temperature stays the same, and the soil is watered every day; the board, tiles and pictures are not to scale.
- The nitrogen atom counter: drag it along one step at a time
- Numbered arrow: a step you have found, from where the nitrogen is to where it goes
- Soil tank: bung in keeps it waterlogged, bung out lets it drain
Use it in your lessons
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