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Nutrient Cycles
8th Grade Science
A Generalized Cycle
Materials often movebetween the regionsof the earth-- Atmosphere- Hydrosphere- Lithosphere- Ecosphere
Cycle Terminology
• Reservoirs: areas where things arestored; things can move in and out
• Sinks: areas where materials are storedover long periods of time and in largequantities
• Fluxes: processes that move materials
Carbon
• Importance: Life on Earth is carbonbased- we are made of molecules thatcontain carbon.
The Carbon CycleReservoirs:
– Ecosphere-Tissues ofplants,animals, fungi,bacteria, etc.
– Lithosphere-top soil
– Atmosphere– Hydrosphere
The Carbon Cycle
Sinks:- Fossil Fuels
(coal, oil,natural gas)
- Rock-limestone
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 burningfossil fuels and wood.
Nitrogen
• Importance: nitrogen in needed to makemany compounds found in the body– DNA– Protein– Enzymes
The Nitrogen Cycle
• Reservoirs/Sinks:– Atmosphere
(78% N2 gas,but we can’tuse it!)
– Ecosphere(tissues ofliving things)
The Nitrogen Cycle
• Our Impact:The Haber-
Bosch Processremoves N2from theatmosphereand use it tomake fertilizer.
• Fluxes– Bacteria perform
many processes inthe nitrogen cycle(nitrogen fixation,ammonification,denitrification,decomposition).
– Lightning– Consumers
Potassium
• Importance: It is a mineral that isneeded for muscle growth and for thenormal function of cells and tissues.
Potassium Cycle
• Reservoirs/sinks:– Lithosphere: Mineral
deposits and surfacesoil
– Ecosphere: Tissuesof living things
Potassium Cycle
• Fluxes:– Weathering– Uptake by plants– Decomposition– Consumers
Phosphorus
• Importance: needed for many biologicalcompounds such as DNA and for boneformation.
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 nutrientssuch as nitrogen or phosphorus in a body ofwater.– 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.