The Nitrogen Cycle - Lab-Aids · •Nitrogen makes up 78% of the air, but most organisms cannot use...

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ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

SGI Ecology: Activity 8 • Living on Earth

The Nitrogen Cycle

1

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Why is nitrogen important?

• Nitrogenisessentialtolivingorganisms

• Itisfoundinallaminoacids,whichmakeupproteins

• ItispartofDNAandRNA

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Where does nitrogen come from?

• Nitrogenisfoundinmanychemicalforms(ammonia,nitrates,etc),onlysomeofwhichcanbeusedbyorganisms

• Nitrogenmakesup78%oftheair,butmostorganismscannotusenitrogendirectlyfromtheair

• Nitrogeniscycledbetweentheatmosphere,organisms,anddifferentreservoirsinaprocesscalledthenitrogencycle

• Duringthiscyclenitrogenistransformedintoseveralchemicalforms

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

The Nitrogen Cycle

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Nitrogen-fixing Bacteria• Nitrogen‐fixingbacteriatransformatmosphericnitrogen(N2)intoammoniumcompounds(NH4

+)

• Symbioticnitrogen‐fixingbacterialiveinrootsoflegumefamilyplant(soy‐beans,peanuts,etc)

• Othertypesofnitrogen‐fixingbacteriaarefoundinthesoil

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Organisms and Nitrogen• Plantsandotherproducersassimilatenitrogen,transformingitfromnitrate(NO3

–)orammonium(NH4

+)ionstoformbiomass.

• Consumersobtainnitrogenfromeatingproducers,orfromeatingotherorganismsthathaveeatenproducers.

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Decomposers and Nitrogen

• Decomposers,primarilybacteriaandfungi,breakdowndeadorganisms.

• Decomposerstransformnitrogenfromorganismsintoammonium(NH4

+)whichgoesintothesoil.

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Nitrifying Bacteria

• Nitrifyingbacteriabreakdownammonium(NH4

+)intonitrite(NO2–)

andthenintonitrate(NO3

–)

• Nitrate(NO3–)

isassimilatedbyorganismsortransformedbydenitrifyingbacteria

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Denitrifying Bacteria

• Nitrate(NO3–)inthesoil

istransformedbydenitrifyingbacteriaintoatmosphericnitrogen(N2).

• DenitrifyingbacteriaalsoproduceN2O,whichcontributestothegreenhouseeffect.

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Atmospheric Nitrogen

• Atmosphericnitrogen(N2)cannotbeuseddirectlybymostproducersorconsumersandmustbetransformedbybacteria.

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

Leaching• Nitrateionsarelostfromthesoilthroughleaching.

• Water‐solublenitrateionsmovewithwaterthroughthesoilandcancontaminatenearbygroundwaterorbodiesofwater.

• Leachingcanleadtopoorsoilconditionsandeutrophicationofcontaminatedwaterbodies.

ECOLOGY•Activity8•LivingonEarth

©2011TheRegentsoftheUniversityofCalifornia

The Nitrogen Cycle