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.