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CYCLES IN THE BIOSPHERE
Nutrients Cycling
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Matter may be transformed from one type to another, but it
cannot be created or destroyed.
This is called the LAW OF CONSERVATION of MATTER.
Nutrients are matter that organisms require for their life
processes.
Macronutrients – those nutrients that are required in large
amounts. (nitrogen, carbon, phosphorus)
Micronutrients – those nutrients needed in smaller amounts.
What goes in must come out?
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Materials on the planet are constantly being used and re-used.
Those materials are moved through different phases on the
planet in biogeochemical cycles.
Biogeochemical means “life-earth-chemical”.
Different items and elements require different amounts of time
to cycle through the environment.
The amount of matter cycled by biogeochemical cycles is
gigantic! For example, about 90 million metric tons (1 metric ton =
1,000 kg or 2,210 lbs) of nitrogen are cycled per year. 90% of it is
done by bacteria.
The major biogeochemical cycles are: the carbon cycle, the
water cycle, the nitrogen cycle, and the phosphorus cycle.
The Nitrogen Cycle
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The nitrogen cycle is the process in
which nitrogen is cycled between
the atmosphere, bacteria, and
other living things.
All living things need nitrogen to
build proteins, which are used to
make new cells.
Nitrogen makes up 78% of the
atmosphere.
BUT…living things cannot use the
nitrogen in the atmosphere…so
how do we get what we need?
The Nitrogen Cycle
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Nitrogen in the atmosphere must
be “fixed” by nitrogen fixing
bacteria in the ground before it
can be used by plants and
animals.
These bacteria live in little nodules
on the roots of plants called
legumes (ie: beans, peas, clover)
or in the soil.
Once the nitrogen is converted into
the right form, animals get that
nitrogen by eating plants that
contain it. Plants get that nitrogen
by absorbing it through their roots
in the soil.
The Nitrogen Cycle
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There is a good amount of nitrogen
in decaying matter and waste.
Decomposers such as fungus and
bacteria break down animal waste,
leaves, dead trees, dead animals,
etc.
During decomposition, nitrogen that
was once in living things is returned
to the soil and some is returned to
the atmosphere.
If decomposers did not exist,
nitrogen would build up in waste and
dead organisms rather than being
returned to the soil to be used again.
The Phosphorous Cycle
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The phosphorous cycle involves the geosphere
and the oceans. It is a key component of cell
membranes, DNA, and RNA.
Although phosphorous is found in living
things…tons more of it is found in rocks, soil,
sediments, and the ocean.
It is released naturally when rocks are broken
down by water or wind. This makes it difficult
for phosphorous to be released.
Plants can only take up phosphorous through
their roots when it is dissolved in water.
The Carbon Cycle
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The carbon cycle is the process in which carbon is
cycled through the land, water, and living things.
On average it takes one carbon atom 300 years to
complete the full carbon cycle.
Carbon is an essential part of proteins, fats, and
carbohydrates.
Carbon is found in all living things.
The Carbon Cycle
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Carbon dioxide found in the
atmosphere is used by plants and
trees to carry out photosynthesis.
During that process, carbohydrates
and oxygen are made.
All living things carry out cellular
respiration, breathing in the
oxygen and using it to create
energy. Living things breath out
and release carbon dioxide back
into the atmosphere.
The Carbon Cycle
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All living things eventually die and
decay = C returned to the ground.
C is compacted into fossil fuels over
millions of years.
Those fossil fuels such as oil, gas,
and coal were once living things.
Fossil fuels are burned to make
vehicles move, heat homes, provide
electricity, etc. When those fossil
fuels are burned, carbon dioxide is
released into the atmosphere.
The Water Cycle
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The water cycle is the
movement of water
from the atmosphere,
to waterways, the
ground, and back to
the atmosphere.
Water is continuously
in motion on our
planet.