The Nitrogen Cycle

The Nitrogen Cycle

1. Importance of Nitrogen

   • Animals
     • In animals, Nitrogen is vital for the production of proteins and muscle functions
   • Plants
     • Nitrogen is important in the groth of plants.

2. Sources of Nitrogen

   • Nitrogen is also stored in oceans and as organic matter in soil.
   • Approximately 78% of Earth's is Nitrogen gas making it the largest source of Nitrogen.
   • Smaller Nitrogen stores are found in terrestrial ecosystems and waterways.

3. Cycles

   • Nitrofication/Denitrofication
     • Nitrification occurs when certain soil bacteria convert ammonium into nitrates (NO3-) and nitrite (NO2-)
     • Nitrogen is returned to the atmosphere via denitrification. In this process, nitrates are converted back to Nitrogen gas. Nitrogen gas is also returned through volcanic eruptions.
   • Nitrogen Fixation
     • In the atmosphere, lightning provides energy for N2 gas to react with O2 gas to form nitrate and ammonium ions.
     • In the soil, Rhizobium convert Nitrogen gas into ammonium ions. These bacteria have a mutualism symbiotic relationship with legumes on which they grow.
     • In the water, cyanobacteria also convert Nitrogen into ammonium during photosynthesis.
   • Nitrogen Uptake
     • Uptake is the process in which nitrates enter plant roots. These nitrogen compounds compose plant proteins. Herbivores then eat the plants and use the Nitrogen for DNA and protein synthesis.

4. The Affect of Human Activities

   • An increase of Nitrogen in an ecosystem can cause certain plant species to out compete other species and decrease resources for all other species in the ecosystem.
   • Nitrogen in the biosphere has doubled in the past 50 years.
   • Burning fossil fuels and treating sewage both release Nitrogen Oxide (NO) and Nitrogen Dioxide (N02)
   • An increase of Nitrogen in the atmosphere can cause acid precipitation (HNO3)