Nitrogen Cycle
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What are the four biological processes that participate in the cycling of nitrogen through the biosphere?
Nitrogen fixation Decomposition / Ammonification Nitrification Dentrification
What are the three processes that are responsible for most of the nitrogen fixation in the biosphere?
Biological fixation by certain microbes Atmospheric fixation by lightning Industrial fixation - haber process
Describe nitrogen fixation
• nitrogen molecule is broken down • so that its atoms require the input of substantial amounts of energy
Describe ammonification
• at each trophic levels - proteins’ etabolism produces organic nitrogen compounds - return to environment mainly as excreted waste • Saprobiontic bacteria break down the molecules in excretions and dead organisms into ammonia
Describe nitrification
• Nitrifying bacteria oxidises NH3 to nitrites • the bacteria then oxidises the nitrites to nitrates - oxidation reactions • nitrifying bacteria requires oxygen • these reactions release heat energy
Define autotroph
An organism that is able to form nutritional organic substances From simple organic substances
Describe dentrification
• dentrification reduces nitrates to nitrogen gas from the atmosphere, thus replenishing the atmosphere • anaerobic bacteria - denitrifying bacteria • waterlogged solids result in more anaerobic denitrifying bacteria being present + less aerobic nitrifying bacteria