Lecture5Nitrogen&Phosphorus

Lecture5Nitrogen&Phosphorus - Global Cycles...

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Global Cycles – Nitrogen & Phosphorus
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Nitrogen Cycle
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1. Oxidation/reduction reactions drive the movement of nitrogen Nitrogen Cycling 3. Nitrogen cycling is also driven by physical factors (lightning/combustion) 2. Nitrogen oxidation/reduction can be driven by an organism’s need for growth , or by an organism’s need for energy 4. Ultimate source of nitrogen to organisms is N 2 from the atmosphere. Many temperate zone ecosystems limited by availability of nitrogen
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Nitrogen Cycle 1. Oxidation/reduction forms of inorganic nitrogen N 2 (nitrogen gas) NH 3 /NH 4 + (ammonia/ammonium) NO 2 -2 (nitrite) NO 3 - (nitrate) NO (nitric oxide) N 2 O (nitrous oxide) N 2 3. NO, N 2 O, N 2 are gases that are lost from ecosystems to the atmosphere 2. NO 3 - and NH 4 + are used by plants and microbes for protein synthesis
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Nitrogen Fixation Nodules on plant roots Nitrogen fixation is the chemical transformation of N 2 to NH 3 Nitrogen fixation is energetically costly Nitrogen fixation is done by microbes, often in a symbiosis with plants
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Lecture5Nitrogen&Phosphorus - Global Cycles...

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