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Mind Map by Brénna Goff, updated more than 1 year ago
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Nitrogen cycle
- The nitrogen cycle ensures that nitrogen within these organic
molecules in the biosphere is constantly recycled so that it may be used
- Saprobiotic nutrition; breaking down dead organisms. Decomposers break down solid
organic matter into soluble substances, first step in the decay of dead organisms
- AMMONIFICATION; ammonia from urea and amino acids. Decomposers and
other microorganisms are also involved in the conversion of organic
nitrogen-containing compounds in urea and amino acids into ammonia. This
process is called ammonification. Ammonia can be lost to the atmosphere,
taken up by plants as ammonium ions, or converted to other forms of
nitrogen.
- NITRIFICATION; ammonium ions (in soil and water) are oxidised to nitrites and
nitrates by nitrifying bacteria. Nitrification requires oxygen, so it happens most
rapidly in well aerated soil or well oxygenated bodies of water. The nitrate ions
produced by nitrification can be taken up by plants and used to make proteins.
- NITROGEN FIXATION; nitrogen to nitrogen compounds. Before plants and
animals can use nitrogen, it must first be converted to absorbable nitrogen
compounds. This is called nitrogen fixation and occurs during
thunderstorms. Lightening provides the energy to oxidise nitrogen -->
nitrogen oxides. The fixation is carried out by nitrogen - fixing bacteria. Some
live free in the soil or water. Nitrogen - fixing bacteria passes an enzyme that
enables them to reduce nitrogen to ammonia or ammonium compounds.
- DENITRIFCATION; nitrates back to nitrogen. The nitrogen cycle is
completed by denitrifying bacteria which live in
conditions of low oxygen and reverse the nitrifying process,
converting nitrates to nitrites, and nitrites into nitrogen gas. The
process is called denitrification and leads to the loss of nitrogen from
the biotic component of an ecosystem to the atmosphere.
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