1.5 The Nitrogen Cycle
Do three things: a photo challenge, a hands-on lab, and a quick check.
Unit 1 · Topic 1.5
Air is 78 percent nitrogen. Why are plants so often starved for it?
Do 1Name the step
Look at the photo. Pick the step or input.
Do 2Put the cycle in order
Do 3Quick check
Your topic score
Key terms
- Nitrogen fixation
- Bacteria (ammonia) and lightning (nitrates) convert N₂ into forms plants can use.
- Nitrification
- Soil bacteria convert ammonium into nitrite and then nitrate.
- Assimilation
- Plants take up nitrate or ammonium and build proteins and DNA.
- Ammonification
- Decomposers convert waste and dead matter back into ammonia.
- Denitrification
- Bacteria in low-oxygen soil convert nitrate back to N₂ gas.
- Limiting nutrient
- The scarcest nutrient, which controls how much a producer can grow.
Photo credits
- Lightning storm. Photo: Nick-K (Nikos Koutoulas) (CC BY 2.0)
- Mushrooms on the forest floor. Photo: Rawpixel (CC0)
- Root nodules on a legume. Photo: Macleay Grass Man (CC BY 2.0)
- Rice paddies, Bali, Indonesia. Photo: Artem Beliaikin (CC0)
- Seedling. Photo: Ruth and Dave (CC BY 2.0)
- Liquid fertilizer application. Photo: eutrophication&hypoxia (CC BY 2.0)
Photos are public domain, CC0, or CC BY. Diagrams and data are original to Green Flask Science.
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