Download 6 Producers. Nitrogen fixers. Decomposers. Nitrogen fixation The

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fixation by
free-living
bacteria in
soil
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Producers.
Nitrogen fixers.
Decomposers.
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Examples of bacteria are in
italics in the yellow boxes.
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denitrification
by bacteria
industrial fixation
eg Haber process
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Nitrogen compounds in the soil
ammonia and
ammonium
compounds
nitrification
bacteria
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nitrification
bacteria
nitrites
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nitrates
fixation by
symbiotic
bacteria
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Putrefaction / ammonification
by decomposers
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Root nodules.
Professor David Day,
University of Sydney
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ammonium compounds
in root nodules of
leguminous plants
Nitrogen fixation
ƒ Symbiotic –
The roots of leguminous plants such as lucerne and clover are invaded by the
bacteria and swellings or nodules containing the bacteria form on the roots;
The bacteria convert nitrogen gas that has been absorbed by the plant from the
soil air into ammonia (NH3) by reduction;
This requires ATP and the enzyme nitrogenase;
The ammonia is further reduced to ammonium ions (NH4+);
Memory aid Rhizobium in Roots.
These are then built into amino acids.
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Nitrogen fixation
ƒ Free-living –
The bacteria convert nitrogen gas in the soil air into ammonia (NH3) by reduction;
This is further reduced to ammonium ions (NH4+);
Some ammonium ions can be taken up by root hairs using active transport;
These are then built into amino acids.
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feeding
nitrogen compounds
in animals
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nitrogen compounds
in plants
death
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active transport
by roots
nitrogen compounds
in dead organisms
excretion
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IB Biology Option F 2012