Nitrogen Cycle

nitrogen

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Nitrification and Denitrification

Nitrification

Ammonium compounds ----> Nitrites ----> Nitrates

NITRIFYING BACTERIA carry this out

Denitrification

Nitrates ----> Nitrogen gas

DENITRIFYING BACTERIA carry this out

ANAEROBIC respiration e.g. in waterlogged soils - no oxygen

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Nitrogen fixing

Nitrogen fixing


Nitrogen ----> Nitrates
NITROGEN FIXING bacteria carry this out.

  • Found in the root nodules of leguminous plants e.g. peas/ beans
  • Symbiotic relationship with plants:
    - bacteria provide plants with nitrogen compounds - plant provides them with nutrients
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Biological Control

Definition: An organism is used to kill off another

Example: Aphids

  • pierce PHLOEM - **** plant sap
  • high pressure --> aphids 'bloat up' + exude sap
  • fungal spores grow in sap --> covers leaf
  • less sunlight reaches + stomata blocked so less C0 absorption
  • less photosynthesis --> less growth

Methods of control:
1. ladybirds
2. encarsia (wasp) - larvae inside, hatch and eat from inside

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Greenhouse Gases

Greenhouse gases: absorb INFRARED radiation e.g. CO and CH

  • Sun's rays enter atmosphere ---> heat up Earth
  • Earth produces INFRARED radiation to cool itself down
  • Some escapes but most ABSORBED and REFLECTED back to Earth by greenhouse gases
  • This warms the Earth up and so the cycle continues...

Ozone: nitrogen oxides react with hydrocarbons in reaction CATALYZED by SUNLIGHT
Smog: mixture of pollutants and particulates

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