Nitrogen Cycle 4.4

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Stages of the Nitrogen Cycle
Ammonification/Putrefaction, Nitrification, Nitrogen fixation, Denitrification
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Ammonification/Putrefaction - Explain
Decomposers (bacteria and fungi) decompose plants, animals, faeces and urine into ammonium ions
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Nitrification - Bacteria
Nitrosomonas - ammonia to nitrite Nitrobacter - nitrite to nitrate Aerobic conditions
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Nitrification - Explain
Ammonium ions converted to nitrites then nitrates. The bacteria require aerobic conditions
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Nitrogen fixation - Bacteria
Azotobacter - free living Rhizobium - root nodules of legumes
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Nitrogen fixation - Azotobacter - Explain
Reduces atmospheric nitrogen (N2) to ammonia - Accounts for most of nitrogen fixation
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Nitrogen fixation - Rhizobium - Explain
Symbiotic relationship - Enzyme nitrogenase reduces atmospheric nitrogen to ammonia - enzyme inhibited by oxygen so haemoglobin is produced in root nodules to protect the enzyme -- Ammonia + organic acid = amino acid
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Root nodule and plant death - benefits
Allow leguminous plants to grow when soil nitrates are scarce. Plant death means that the nodules break down and the bacteria and ammonium is released into the soil
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Denitrification - Bacteria
Pseudomonas - anaerobic- nitrates + ammonia back to atmospheric nitrogen
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Denitrification - Explain
Nitrogen lost from ecosystem to atmosphere. Waterlogged fields = anaerobic conditions = denitrifying bacteria.
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Improve circulation of nitrogen - Human activities (4)
Sewage disposal, Animal waste from farming stock used as manure (ammonification), Feritilisers fix atmospheric nitrogen artificially, using microorganisms for compost
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Improve circulation of nitrogen - Farming practices (3)
Planting fields of clover (legume) encourages nitrogen fixation, Draining land to reduce anerobic conditions, Ploughing fields to improve soil aeration.
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Other cards in this set

Card 2

Front

Ammonification/Putrefaction - Explain

Back

Decomposers (bacteria and fungi) decompose plants, animals, faeces and urine into ammonium ions

Card 3

Front

Nitrification - Bacteria

Back

Preview of the front of card 3

Card 4

Front

Nitrification - Explain

Back

Preview of the front of card 4

Card 5

Front

Nitrogen fixation - Bacteria

Back

Preview of the front of card 5
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