09 bio 07

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09 bio 07

  1. 1. Nitrogen Cycle
  2. 2. • Nitrogen is needed to make protein and DNA.• N2 (nitrogen gas) is the most abundant gas in the atmosphere (78%)• However, it is not in a usable form for plants to take up.• Animals obtain the nitrates (NO3−) from eating plants.
  3. 3. Nitrogen Fixation• Nitrogen fixation is the process of turning nitrogen gas into a useable form, nitrate, NO3-• Two methods: a) lightning strikes b) by certain types of bacteria which live in the soil.
  4. 4. Nitrogen in Agriculture• Farmers often plant crops like alfalfa and clover to increase the nitrate, NO3-, levels in the soil.• Soil is often aerated (holes are put dug) to allow oxygen to facilitate the process of nitrogen fixation.• Fertilizers also increased the nitrate level.• Sometimes the extra nitrogen runs off into the local stream and river
  5. 5. Denitrification• There are some bacteria (called denitrifying bacteria) which will break down the nitrate, NO3 - back to nitrogen gas in a process called denitrification.

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