The nitrogen cycle
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The nitrogen cycle. Why is the cycle important and what is nitrogen used for?. Not many organisms can use nitrogen directly from the air (78%) Recycling of nitrates allows plants to manufacture proteins for growth. Therefore it is a limiting factor for yield/ dry mass. 4 Main stages.

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The nitrogen cycle

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The nitrogen cycle


Why is the cycle important and what is nitrogen used for?

  • Not many organisms can use nitrogen directly from the air (78%)

  • Recycling of nitrates allows plants to manufacture proteins for growth.

  • Therefore it is a limiting factor for yield/ dry mass


4 Main stages

  • Ammonification- production of ammonia from organic compounds.

  • Nitrification- Conversion of ammonium ions to nitrate ions.

  • Nitrogen fixing:

  • 1) Free living bacteria- nitrogen gas reduced to ammonia.

  • 2) Mutualistic bacteria- symbiotic relationship with plants.

  • Denitrification- Conversion of ammonium ions to gaseous nitrogen.


Non-living/ living stages

  • Nitrogen in the soil is classed as a non-living phase of the cycle.

  • When ions are absorbed or fixed through nodules into producers, consumers and decomposers the ammonium in the macromolecules becomes part of the living phase.


Final links/ processes in the cycle

  • Death and excretion- Saprobiotic organisms break down urea or dead organisms into ammonium ions.

  • Absorption- Nitrate ions actively transported through root hair cells.

  • Feeding- Consumers obtain nitrates from digestion.


Put it all together

Non-living

living

Nitrogen fixing (free living bacteria)

Ammonium ions

Nitrogen in the atmosphere

Nitrite ions

Nitrate ions

Nitrification

De-nitrification

Nitrogen fixation (mutualistic bacteria)

Absorption

Ammonium containing molecules (protein)

Producers

Ammonium containing molecules (protein)

Consumers

Digestion

Death

Death and excretion

Ammonification

Ammonium containing molecules (protein)

Decomposers


Typical questions

  • Where and how does nitrogen entre the living and non-living stages of the nitrogen cycle?

  • How is nitrogen recycled in the nitrogen cycle?

  • Why do farmers achieve a faster rate of crop growth when they plough?


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