Abiotic Cycles 22.2

8/14/2019 Abiotic Cycles 22.2

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Definebiogeochemicalycle.o

Tracehestepsf hewater ycle.I

Summarizehemajortepsin henitrogenycle.

aDescribehestepsof he arbonycle.

HC*$Y$?E11[ncYCIINWnit" energ)/ lows hroughon ecosystem,ater andminerals,such as carbon,nitrogen,calcium, and phosphorusare recycled and reused.Each substancetrauels through abiogeochemical (wt-oh-ctt-oh-KEM-i_kuhl) cycle, mou ingfrom the abiotic portion of the enuironment, suchas theatmosphere, nto liuing things,and back again.

THE \ruATER CYCLEwater is crucial to life. cells contain 70 percent to 90 percent watand water provides the aqueous environment in which most of litechemical reactions occur. The availability of water is one of the kfactors that regulate the productivity of terrestrial ecosystemHowever, very little of the available water on Earth is trapped withliving things at any given time. Bodiesof water such as lakes, ivestreams, and the oceans contain a substantial percentage of tEarth's water. The atmosphere also contains water-in the formwater vapor. In addition, some water is found below ground. wain the soil or in underground.folmationsof porous rock is known

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FIGURE2- 5I In hewater ycle,aterallsoEarth'sI surfacesprecipitation.ome aterI reentersheatmosphereyevaporationI and ranspiration.om e aterun snt oI streams,akes,ivers,nd ceans.0therI water eepshroughhesoil nd ntoI theground ater.ollowhepathwaysI of hewater yclen he igure.

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ground water. The movement of water between these various reser-'.oirs, known as the water cycle, is illustrated in Figure22-5.Three important processes in the water cycle are evaporation,:ranspiration, and precipitation. Evaporation adds water as vapor:o the atmosphere. Heat causes water to evaporate from the,:(eans and other bodies of water, from the soil, and from the bod_resof living things. At least 90 percent of the water that evaporates:rom terrestrial ecosystems passes through plants in a processcalledtranspiration. In transpiration, plants take in water throughireir roots, and they release water and take in carbon dioxideirrough the stomata in their leaves.Animals also participate in the'h,-atercycle, but their impact is less significant than that of plants.Animals drink water or obtain it from their food. They release hisb-aterwhen they breathe, sweat, or excrete.water leaves he atmosphere through precipitation. The amountn[ rrater the atmosphere can hold depends on abiotic factors, suchds temperature and air pressure. once the atmosphere becomessarurated with water vapor, precipitation occurs in the form ofraia.snow, sleet, hail, or fog.

TFIE CARBON CYCLEliliiryether, hotosynthesis and cellular respiration form the basis of' '- carbon cycle, which is illustrated in Figure22-6.During photos5m_tfdi'tpsis.lants and other autbtrophs use carbon dioxide (COr), alongmfi water and solar energy, o make carbohydrates. Both autotrophs;snr heterotrophs use oxygen to break down carbohydrates during

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Modeling Ground WaterMaterials isposableloves,abapron,Lplasticottlecu tnhalf),mall tones250mL), rysodwithgrass,atet, raduatedcylinder,00mL eakerProcedureoc1. Put nyourabapron nddisposableloves.2. Inverthe op halfof heplasticbottle ndplacet insidehebottomhalfof thebottle oforma column.3. Placehestonesn hebottomof he nvertedop halfof hebottle. lace chunk f drysodwithgrass n op of hesrones.4. Pour 50mL.of ater ver hesod,andobserveow hewaterpenetrateshesoilan dmovesthroughhecolumn.5. Whenhewater sno ongerdraining,emovehe ophalfof hecolumn ndpour hewater rom he bottom f thecolumnnt oa beaker. easure

th evolume f iquidn hebeaker.Analysis What s hevolume fth ewater hatdrainedhroughth esod?Ho wmuch f hewaterremainedn hesoil?Where oe sth ewater owhenappliedo areal aw nor crop?Whatmighthefateof fertilizer r pesticidesethatar eappliedo a lawnor crop?

Carbonxistsn heatmospheren heformof carbon ioxide. ellularesoira-tion, ombustion,nddecompositionof organicmatter re he hreemajorsourcesf carbon ioxide. yburninglarge mountsf ossiluels, umansare ncreasingheamount f carbondioxiden heatmosphere.

\ Photosynthesis\'-"-trCombustion

ellularrespiration I$-T -* r^ .Es&.

Death anddecomposition

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cellular respiration.The byproducts of cellular respirationare carbdioxide and water. Decomposers release carbon dioxide into :' -atmospherewhen they break down organiccompounds.F{urc"ae.E'tr:?aaeraeexr EeeCarb*ea Cy*E*In the last 150 years, the concentration of carbon dioxide in t:,atmosphere has risen nearly 30 percent. Almost half of this increa..has occurred in the last 40 years. Human activities are responsi: -for the increase. Our industrial society depends on the ener.-released by the burning of fossil fuels-coal, oil, and natural ga'.Fossil uels are the remains of organisms hat have beentransforrni:by decay, heat, and pressure into energy-rich organic molecule'.Burning releases he energy in these molecules,but it also releas=":carbon dioxide. Carbon dioxide is also added to the atmosphere :the burning of vegetation.Today arge areasof tropical rain forest ar.being burned to create farmland and pasture for cattle. The burnir-of vegetation adds carbon dioxide to the atmosphere, and tf-.destruction of vegetationremoves plants that could have absorb'::carbon dioxide from the atmosphere hrough photosynthesis.

fr1rxnNEEe*GsruvcLwAII organismsneed nitrogen to make proteins an d nucleic acic.The complex pathway that nitrogen followswithin an ecosystem .called the nitrogen cycle. Consider how nitrogen cycles within ti-.terrestrial ecosystemshown in Figure22-7.Nitrogen gas,Nr , mak:.up about 78percent of the atmosphere,so it might seem hat njtr--gen would be readily available or living things.However,shortag=.

FIGURE 2-7This igure howshecycling f nitro-genwithinan ecosystem.acteriareresponsibleor many f the stepsn thenitrogenycle,ncludingheconversionof atmosphericitrogenntoammonia.Nitrogen{ixingacteriaive n hesoilor n he roots f plants. lantsakeupth eammoniaroducedy hebacteria.Animalsetnitrogenyeating lantsor other nimals.

Denitrifying \bacteria

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Death Waste Deathi (urine and feces)

Decomposers

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Ammonif icat ioni' \ *w#'

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Nitrates S- b(Nor) b*&tr


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of nitrogen often limit the productivity of plants-and therefore theproductivity of ecosystems.Most plants can use nitrogen only inihe form of nitrate. The process of converting nitrogen gas to:ritrate s called nitrogen fixation. organisms rely on the actions oflacteria that are able to transform nitrogen gas nto a usable form.separate groups of nitrogen-fixing bacteria convert nitrogen gasurto ammonia, hen nitrite, and then nitrate, which plants ca n use.Nitrogen-fixingbacteria live in the soil and in the roots of somehindsof plants,such as beans,peas,clover,and alfalfa.These plantsinve evolveda complex mutualistic relationshipwith nitrogen-fixingaacteria. The plant provides the bacteria with a home-airtightsu'ellingson its roots-and supplies them with carbohydrates. Inatchange, he bacteria produce usablenitrogen for the plant. Excessitrogen produced by the bacteria is released nto the soil.Recycling NitrogenThe bodies of dead organisms contain nitrogen, mainly in proteinsand nucleic acids. Urine an d dung also contain nitrogen. Decom-fosers break down the corpses and wastes of organisms andrclease the nitrogen they contain as ammonia. This process isffiiown as ammonification (ah-vntru-i-fi-KAy-shuhn).hrough ammon_Ldcation, itrogen that would otherwise be lost is reintroduced into:he'ecosystem.

Bacteria n the soil take up ammonia and oxidize t into nitrites,IO , , an d nitrates, NOr-. This process, called nitrificationm:-tri-fi-KAY-shuhn),s carried ou t by bacteria.The erosion of nitrate-nch rocks also releases nitrates into an ecosystem. plants usea.itrates o form amino acids. Nitrogen is returned to the atmos-F,irerehrough denitrification. Denitrification occurs when anaero-n,icbacteria break down nitrates and releasenitrogen gasback intorne atmosphere.

Plants can absorb nitrates from the soil, but animals cannot.Animals obtain nitrogen in the same way they obtain energy_byeating plants and other organisms and then digesting the proteins;andnucleic acids.

1. Descibe he biogeochemicalycle.2. Where o nitrogen-fixingacteriaive?Whatcrucialunction o theyperform?3. Describehe roleof decomposersn the nitrogencycle.4. Howhas he burning f fossil uelsaffectedhecarbon ycle?

5. Through hat process oesmostwatervaporenter he atmosphere?xplainhe process.6. CRITICALHINKING Exptainwo ways ha t heburning f vegetation ffects arbon ioxideev-els n theatmosphere.owdo yo u hink heremoval f vegetation ffectsoxygenevels nthe atmosphere?

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Abiotic Cycles 22.2