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Nutrient Cycles
8th Grade Science
A Generalized Cycle
Materials often move
between the regions of
the earth- Atmosphere
- Hydrosphere
- Lithosphere
- Ecosphere
Cycle Terminology


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Reservoirs: areas where things are stored;
things can move in and out
Sinks: areas where materials are stored over
long periods of time and in large quantities
Fluxes: processes that move materials
Carbon

Importance: Life on Earth is carbon based- we
are made of molecules that contain carbon.
The Carbon Cycle
Reservoirs:




BiosphereTissues of
plants, animals,
fungi, bacteria,
etc.
Lithospheretop soil
Atmosphere
Hydrosphere
The Carbon Cycle
Sinks:
- Fossil Fuels
(coal, oil,
natural gas)
- Rock- limestone
The Carbon Cycle
Fluxes:
- Photosynthesis
- Respiration
- Burning fossil
fuels
- Burning trees
- Decomposition
- Consumers
The Carbon Cycle
Human Impact:
Humans have
increased the
amount of CO2
in the
atmosphere
from burning
fossil fuels and
wood.
Nitrogen

Importance: nitrogen is needed to make many
compounds found in the body



DNA
Protein
Enzymes
The Nitrogen Cycle

Reservoirs/Sinks:


Atmosphere (78%
N2 gas, but we
can’t use it!)
Ecosphere (tissues
of living things)
The Nitrogen Cycle

Fluxes

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
Bacteria perform
many processes in
the nitrogen cycle
(nitrogen fixation,
ammonification,
denitrification,
decomposition).
Lightning
Consumers
The Nitrogen Cycle

Our Impact:
The Haber-Bosch
Process removes
N2 from the
atmosphere and
use it to make
fertilizer.
Potassium

Importance: It is a mineral that is needed for
muscle growth and for the normal function of
cells and tissues.
Potassium Cycle

Reservoirs/sinks:


Lithosphere: Mineral
deposits and surface soil
Ecosphere: Tissues of
living things
Potassium Cycle

Fluxes:

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
Weathering
Uptake by plants
Decomposition
Consumers
Phosphorus

Importance: needed for many biological
compounds such as DNA and for bone
formation.
Phosphorus Cycle

Reservoirs/Sinks:


Lithosphere: Earth’s
crust and top soil
Ecosphere: tissue of
living things
Phosphorus Cycle

Fluxes:



Decomposers
Consumers
Weathering of rocks
Phosphorus Cycle

Human Impact: Runoff from farms contains
high levels of
phosphorus which make
their way into streams,
rivers, etc.
Too much of a good thing:

Eutrophication: build-up of too many nutrients
such as nitrogen or phosphorus in a body of
water.

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Excess nutrients cause excessive algae growth.
The algae blocks sunlight from reaching the
bottom, causing other algae to die.
The algae at the surface die and fall to the bottom.
Feces from fish and zooplankton that feed off the
algae fall to the bottom


Bacteria populations increase and feed off of the
dead algae and feces and use up all the oxygen in
the water.
Low oxygen levels cause other aquatic organisms
to die or leave the area.
Eutrophication
Eutrophication