Today we

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Today were going to look at nutrient cycling in
the environment particularly at the nitrogen
cycle.
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The Importance of Nitrogen
Why is nitrogen important to living things?
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The Importance of Nitrogen
Proteins contain the elements carbon, hydrogen,
oxygen and nitrogen Proteins are made of units
called amino acids.
Proteins are essential for growth and repair of
body tissues in all living things.
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The Importance of Nitrogen
We and other animals need amino acids to make the
proteins to build our bodies our proteins from
protein rich foods such as
Eggs Red and white meat Fish dairy
products beans lentils peas nuts
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The Importance of Nitrogen
Most plants make their own proteins using
nitrogen. But not from the air as they cant
absorb gaseous nitrogen. instead they absorb it
through their roots as nitrates from the soil
that they grow in.
Fertilisers contain nitrates to help with this.
Animals then eat plants digest the protein and
absorb the amino acids that they are made from
into their blood to be carried to where they are
needed to make protein for growth and repair.
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If all this nitrogen ends up in living things
why doesnt it run out?
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Not all of the protein in plants or prey eaten by
animals end up being absorbed. A lot of it comes
out in faeces (dung).
In the bodies of animals excess amino acids not
needed for making protein for growth and repair
are broken down into urea- a nitrogenous waste
(meaning it contains nitrogen).
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The proteins in dead bodies and dung and
nitrogenous wastes are broken down by bacteria
and fungi (decomposers) into ammonia. This
ammonia is then made into nitrates by bacteria.
Lets summarise all of this.
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ANIMAL PROTEIN
Death and excretion
Eating
DEAD ORGANISMS AND DUNG
Death
PLANT PROTEIN
Decay by fungi and bacteria
AMMONIA
Uptake by roots
NITRITES THEN INTO NITRATES
Conversion by bacteria
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nitrogen fixing bacteria
Other bacteria take nitrogen from the air and
convert it to a form that plants can use some
live free in the soil and others such as
Rhizobium live in a special relationship with
legumes- plants such as peas, beans and clover.
Here is a clover plant showing the root nodules
in which the Rhizobium lives.
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NITROGEN GAS IN THE AIR
Nitrogen fixing bacteria
Denitrifying bacteria
ANIMAL PROTEIN
In the roots of peas, beans and clover (legumes)
and free in soil.
Death and excretion
Eating
DEAD ORGANISMS AND DUNG
Death
PLANT PROTEIN
Decay by fungi and bacteria
AMMONIA
Uptake by roots
NITRITES THEN INTO NITRATES
Conversion by bacteria
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A
F
G or E
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E
F
D
B
C
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Summary video- WARNING- This has some bad words
in it and so may not be suitable for your
teacher!
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5.
thrush
snail
grass
A habitat is the place where an organism lives.
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Bacteria or fungi.
Decomposers break down organic matter by
respiration. In the nitrogen cycle they convert
protein and nitrogenous wastes into ammonium and
nitrates that may be used by plants to build
protein.
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6.
oak
wood mouse/ shrew/owl/fox
fungi
squirrel/ caterpillar
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oak
caterpillar
shrew
fox
wood mouse
earth worm
leaf litter
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9.
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13.
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nitrate
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nitrifying bacterium
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Learning Outcomes

• Animal and plant proteins are made up of amino
  acids that contain the element nitrogen.
• Plants and animals cannot absorb nitrogen from
  the air.
• Plants gain their nitrogen in the form of
  nitrates through their roots in a process known
  as uptake.
• Nitrifying bacteria convert ammonia into
  nitrates.
• Denitrifying bacteria convert nitrates into
  nitrogen gas.
• Nitrogen fixing bacteria convert nitrogen from
  the air to a form that plants can use. Some are
  found free in the soil and others in the root
  nodules of legumes (peas beans and clover).
• Decomposers (bacteria and fungi) convert proteins
  and nitrogenous waste in urine and faeces (pee
  and poo) into ammonia.