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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
• 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:
– EcosphereTissues of
plants,
animals, fungi,
bacteria, etc.
– Lithospheretop soil
– Atmosphere
– Hydrosphere
The Carbon Cycle
Fluxes:
- Photosynthesis
- Respiration
- Burning fossil fuels
- Burning trees
- Decomposition
- Consumers
Sinks:
- Fossil Fuels
(coal, oil,
natural gas)
- Rocklimestone
The Carbon Cycle
Human Impact:
Humans have increased the amount of
CO2 in the atmosphere from burning
fossil fuels and wood.
Nitrogen
• Importance: nitrogen in needed to make
many compounds found in the body
– DNA
– Protein
– Enzymes
The Nitrogen Cycle
• Reservoirs/Sink
s:
– Atmosphere
(78% N2 gas,
but we can’t
use it!)
– Ecosphere
(tissues of
living things)
The Nitrogen Cycle
• Fluxes
– Bacteria perform
many processes in
the nitrogen cycle
(nitrogen fixation,
ammonification,
denitrification,
decomposition).
– Lightning
– Consumers
• Our Impact:
The HaberBosch 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:
–
–
–
–
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
• Human Impact:
– Run-off 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.
– Excess nutrients cause excessive algae growth.
– The algae blocks sunlight from reaching the
bottom, causing other algae to die.
– Bacteria populations increase and feed off of the
dead algae and use up all the oxygen in the water.
– Low oxygen levels cause other aquatic organisms
to die to leave the area.