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Published byBrock Armfield Modified over 9 years ago
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The nitrogen cycle
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Why is the cycle important and what is nitrogen used for? Not many organisms can use nitrogen directly from the air (78%) Recycling of nitrates allows plants to manufacture proteins for growth. Therefore it is a limiting factor for yield/ dry mass
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4 Main stages Ammonification- production of ammonia from organic compounds. Nitrification- Conversion of ammonium ions to nitrate ions. Nitrogen fixing: 1) Free living bacteria- nitrogen gas reduced to ammonia. 2) Mutualistic bacteria- symbiotic relationship with plants. Denitrification- Conversion of ammonium ions to gaseous nitrogen.
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Non-living/ living stages Nitrogen in the soil is classed as a non-living phase of the cycle. When ions are absorbed or fixed through nodules into producers, consumers and decomposers the ammonium in the macromolecules becomes part of the living phase.
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Final links/ processes in the cycle Death and excretion- Saprobiotic organisms break down urea or dead organisms into ammonium ions. Absorption- Nitrate ions actively transported through root hair cells. Feeding- Consumers obtain nitrates from digestion.
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Put it all together Ammonium ions Nitrite ions Nitrate ions Nitrogen in the atmosphere Nitrogen fixing (free living bacteria) Nitrification De-nitrification Ammonium containing molecules (protein) Producers Ammonium containing molecules (protein) Consumers Ammonium containing molecules (protein) Decomposers Absorption Digestion Nitrogen fixation (mutualistic bacteria) Death Death and excretion Ammonification Non-living living
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Typical questions Where and how does nitrogen entre the living and non-living stages of the nitrogen cycle? How is nitrogen recycled in the nitrogen cycle? Why do farmers achieve a faster rate of crop growth when they plough?
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