An atom exists in a gas molecule in the atmosphere. It passes by the nodules of a bean plant, where it is converted into ammonia and absorbed into the soil. Bacteria in the soil then convert the ammonia into a form that can be reabsorbed by the bean plant. When the bean plant dies and decomposes, anaerobic bacteria incorporate the atom into a gas molecule, which returns to the atmosphere. Which geochemical cycle does this sequence describe?
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Water cycle |
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Carbon cycle |
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Nitrogen cycle |
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Phosphorus cycle |
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Sulfur cycle |
