Science 9 - Nitrogen Cycle

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the NitrogenCycle
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Nitrogen Cycle?

• A nutrient cycle in which nitrogen atoms are
  circulated through the living and non-living
  environment
• Problem
• 79 of atmosphere made of nitrogen (N2)
• Living things cant use nitrogen directly

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Getting Nitrogen

• Organisms cant get nitrogen directly, so get it
  in a usable form called nitrates

Nitrogen (N2) (in atmosphere)
Nitrates(NO3)-
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Getting Nitrogen

• Examples
• Heterotrophs animals obtain nitrogen stored in
  the food they eat
• Autotrophs plants obtain nitrogen in the form of
  nitrates from soil

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Why is Nitrogen Important?

• Nitrogen atoms are an important part of
• Proteins building material of
  living things.
• Example muscles are made of protein

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Lawn with little nitrogen
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Lawn with adequate nitrogen
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Fertilizer source of nitrogen
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Fertilizer source of nitrogen
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Protein in hemoglobin (Blood)
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Protein in muscles
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Protein in hair
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Protein in Fingernails
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Why is Nitrogen Important?

• DNA molecule in body which contains
  hereditary information (instructions for
  life)

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Steps of the Nitrogen Cycle
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Overview

• Nitrogen cycle
• Nitrogen Fixation Obtaining nitrogen from air,
  to be used by living things
• Denitrification Returning nitrogen back into the
  air

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Nitrogen Fixation

• Nitrogen Fixation is conversion of nitrogen from
  atmosphere into nitrates to be used by plants
• Nitrogen Nitrates
• ?
• Nitrogen Fixation occurs in two ways 1)
  lightning and 2) nitrogen fixing bacteria

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1) Lightning

• Energy from converts nitrogen and oxygen in the
  air into nitrates.

• Energy Nitrogen Oxygen ? Nitrates

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1) Lightning (cont)

• Rain carries nitrates down into soil
• Plants absorb nitrates and water through their
  roots
• Note nitrates contain nitrogen!

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1) Lightning (cont)

• Plants stored nitrogen in their bodies
• Nitrogen is passed through the food webs in the
  food we eat.

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2) Nitrogen Fixing Bacteria

• Bacteria in the soil convert nitrogen into
  nitrates.
• Why?
• Bacteria get food (sugar) from plants
• Bacteria release nitrates into soil which plants
  absorb

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2) Nitrogen Fixing Bacteria (nodules)
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2) Nitrogen Fixing Bacteria

• NOTE not all plants have nitrogen fixing
  bacteria, only legumes (clover, pea, alfalfa).

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2) Nitrogen Fixing Bacteria

• QUESTION How would clovers growing on your front
  lawn benefit the grass?

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Denitrification

• The opposite of nitrogen fixation
• Bacteria convert nitrates into nitrogen
• Completes nitrogen cycle, ensures a balance of
  nitrates in soil and nitrogen in atmosphere

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Decomposers

• When an animal dies, its body contains nitrogen
  (obtained from the food eaten)
• Decomposers help release this nitrogen back into
  the nitrogen cycle

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INTERFERING WITH THE NITROGEN CYCLE
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SUBSISTENCE FARMING

• Natural farming. Farming to the natural
  tolerance of the soil.
• Advantage does not overuse the soil, no
  fertilizers, eco-friendly
• Disadvantage small amounts of food

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SUBSISTENCE FARMING
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COMMERCIAL FARMING

• This is large scale farming, in which fields are
  overplanted
• Crop plants use up naturally occurring nitrates
  in the soil

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ONTARIOs GREEN BELT
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NIAGRA the Fruit belt
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• Problem
• Crops planted yearly, using up all nitrogen in
  soil
• Nitrogen needs to be replaced

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Commercial farming

• Replace nitrogen by placing
• Chemical Fertilizers or Natural Fertilizers
  (manure) directly into the soil

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Algal bloom

• Fertilizers washed out by rain into streams and
  rivers
• Extra nitrogen stimulates growth of water plants
• Plants use up all oxygen in the water

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Algal bloom

• Plants use up all oxygen in the water
• Kills all life in the pond

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Algal bloom
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Algal Bloom