SME
Grade 9 Science · Problem type
The nitrogen cycle
Use this for “How do plants such as beans add nitrogen to the soil?”
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Nitrogen goes from the air into the soil, through living things and back to the air.
Assumptions
•
Air is mostly nitrogen gas, N₂, but plants and animals cannot use it in that form.
•
Living things need nitrogen to build amino acids, so proteins, and the bases of DNA.
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Ecosystems: energy pyramids, matter cycles, succession and biodiversity
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Use this for “How do photosynthesis and respiration move carbon between the air and living things?”