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Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

water(H2O).Oxygenhastwonaturallyoccurringvariantscalledisotopes;theyhavethe samechemicalpropertiesbutdifferentweightsbecausetheirnucleihavedifferentnumberso neutrons.BothisotopesofOareincorporatedintothebodiesofanimalsthatconsumethe isotopesinwaterandfood.

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Thehardsurfaceofteeth,calledenamel,ismadeuplargelyofcalciumphosphate, Ca3(PO4)2.Theisotopecompositionoftheoxygenincalciumphosphateenamelvaries dependingonwhereananimalwaslivingwhentheenamelwasmade.Whenwater evaporatesfromtheocean,itformscloudsthatmoveinlandandreleaserain.Waterwiththe heavierisotopeofOtendstofallmorereadilythanwatercontainingthelighterisotope.Asa result,regionsoftheworldthatareclosertotheoceanreceiveraincontainingmoreheavy waterthandoregionsfartheraway,andthesedifferencesarereflectedinthebodiesof animalsthatdwellintheseregions.

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

QandA

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1. Whatinsightsintobiologicalsystemshavebeendiscoveredthroughisotope analysis?(Findtheansweronpage40.)

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

KEYCONCEPT2.1 AnElement’sAtomicStructureDeterminesIts Properties LearningObjectives 2.1.1Comparetheelementsfoundinlivingtissuewithelementsfoundinnonliving matter. 2.1.2Relatetheatomicstructureofanatomtoitsidentityasanelement. 2.1.3Explaintherolethattheoutermostelectronshellplaysindetermininghowan atommaycombinewithotheratoms. 2.1.4Explainhowelementscanbegroupedintocolumnsontheperiodictable accordingtotheirchemicalproperties.

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Allmatteriscomposedofatoms.Atomsaretiny—morethanatrillion(1012)ofthemcould makeuptheperiodattheendofthissentence.Atomsandtheircomponentparticleshave volumeandmass,whicharecharacteristicsofallmatter.Massisameasureofthequantityo matterpresent;thegreaterthemass,thegreaterthequantityofmatter.Atomsalsohave electriccharges.

Atomscontainprotons,neutrons,and electrons Eachatomconsistsofadense,positivelychargednucleus,aroundwhichareoneormore negativelychargedelectrons(Figure2.1).Thenucleuscontainsoneormorepositively chargedprotonsandmaycontainoneormoreneutronswithnoelectriccharge.

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

aroundoutsidethenucleushaveaminussign,withacalloutreading,"Eachelectronhas negligiblemassandanegativecharge.” Themassofaprotonservesasastandardunitofmeasurecalledthedalton(namedafterthe EnglishchemistJohnDalton).Asingleprotonorneutronhasamassofabout1dalton(Da), whichis1.7×10−24grams(0.0000000000000000000000017g),butanelectronhaseven lessmassat9×10−28g(0.0005Da).Becausethemassofanelectronisnegligiblecompared withthemassofaprotonoraneutron,thecontributionofelectronstothemassofanatom canusuallybeignoredwhenmeasurementsandcalculationsaremade.Itiselectrons, however,thatdeterminehowatomswillcombinewithotheratomstoformstable associations. Eachprotonhasapositiveelectriccharge,definedas+1unitofcharge.Anelectronhasa negativechargeequalandoppositetothatofaproton(–1).Theneutron,asitsname suggests,iselectricallyneutral,soitschargeis0.Chargesthataredifferent(+/−)attracteach other,whereaschargesthatarealike(+/+,−/−)repeleachother.Generally,atomsare electricallyneutralbecausethenumberofelectronsinanatomequalsthenumberofprotons.

Anelementconsistsofonlyonekindofatom

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Anelementisafundamentalsubstancethatcontainsonlyonekindofatom.Theelement hydrogenconsistsonlyofhydrogenatoms;theelementironconsistsonlyofironatoms.The atomsofeachelementhavecharacteristicsthatdistinguishthemfromtheatomsofother elements.Thesephysicalandchemicalproperties(howtheyinteractwithotheratoms) dependonthenumbersofparticlestheatomscontain. Therearemorethan100differentelements,althoughonly92ofthemoccurnaturally.About 98%ofthetissueofeverylivingorganism(exceptinskeletons)iscomposedofjustsix elements: Carbon(symbolC) Hydrogen(H) Nitrogen(N) Oxygen(O) Phosphorus(P) Sulfur(S) Althoughlivingorganismsarecomposedofthesameelementsasthenonlivinguniverse,the proportionsinlivingsystemsareverydifferent.Forexample,oxygenmakesup65%ofthe humanbody(excludingbones).Butitmakesup21%ofEarth’satmosphereand46%of Earth’scrust.Carbonmakesup18%ofthehumanbodybutlessthan1%Earth’satmosphere anditscrust.Silicon,bycontrast,makesuplessthan0.01%ofthehumanbodyandisabsent fromouratmosphere,butitmakesup28%ofEarth’scrust.Clearly,livingsystemsare

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Forexample,therearethreeisotopesofcarbon:12C(sixneutronsinthenucleus),13C (sevenneutrons),and14C(eightneutrons).Notethatallthree(calledcarbon-12,carbon-13, andcarbon-14)havesixprotons,sotheyareallcarbon.Mostcarbonatomsare12C,about 1.1%are13C,andatinyfractionare14C.Thecarbonatomsthatmakeupcomplex biologicalmoleculesaremostly12C,butsomeare13C.Theratioof13C:12Cvarieswith locationandcanbeusedtoidentifybiologicalsampleswhoseoriginisnotknown (InvestigatingLife:DeterminingBeefSourceinBigMacsUsingIsotopeAnalysis).All carbonisotopeshavevirtuallythesamechemicalreactivity,whichisanimportantproperty fortheiruseinexperimentalbiologyandmedicine. ▶InvestigatingLIFE DeterminingBeefSourceinBigMacsUsingIsotopeAnalysis Experiment

OriginalPaper:L.Martinellietal.2011.Worldwidestablecarbonandnitrogenisotopesof BigMacpatties:Anexampleofatruly“glocal”food.FoodChem127:1712–1718.

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TheBigMachamburgercanbepurchasedin38,000outletsin120countries.Therecipefor theBigMacisvirtuallythesameeverywhere;itisclaimedthattheburgerhasthesame qualitymeatandnutritionalqualityeverywhereitisserved.Toinvestigatethisclaim,Lesley ChessonandJamesEhleringerattheUniversityofUtahcomparedtheratioof13C:12Cin BigMacpattiesaroundtheworldtodeterminewhetherthemeathadalocaloracommon source.Beefcattleeatplantfood,andcarbonatomsfromthisfoodendupinmeat.Insome typesofplants,theratioof13C:12Cishigherthaninothers.Dependingonwhichtypeof plantsthecattleconsume,thebeefwillalsohaveadifferent13C:12Cratio.

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

•3c:"Ionsacceleratetowardschargedslit."Adiscwithahorizontalslitsitswithinthetube. •3d:"Magneticfielddetectslightestionsmost."Twoflatelectromagnetssitoneithersideof thetube. •3e:"Ionsseparatedbymasscanbemeasured."Particleswithinthetubeareseparatedwith blueparticlesatthebottomandredparticlesatthetop. UndertheResultsheadingisabargraphshowingthatthecarbon-13ratioishigherinmeat fromtheUSBigMacthaninmeatfromtheChineseBigMac.Therearetwobars,labeled “China”and“UnitedStates.”TheY-axisislabeled“13-Cratio(ppm)”andshowsvalues from0.136to0.146inincrementsof0.002.TheChinabarisatapproximately0.139,andthe UnitedStatesbarisatapproximately0.1445. ThisisasamplecontentforLongALTtext

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WorkwiththeData

TheexperimentcomparedthemeatinBigMacsservedin26differentcountriesby measuringtheratioofstablecarbonisotopes(13C:12C)insamplesoftenbeefpattiesfrom eachcountry.ThehypothesiswasbasedonclaimsthatthebeefusedinBigMacscomesfrom asinglesource,andthatthe13C:12Cratioinpattiesfoundeverywhereshouldthusbethe same.TableAshowstheaverage13C:12Cratioforeachofthe26countries.Ahigher numbermeansmoreoftherare,stableisotope13Cthanofthemorecommon12C. TableA Country 13C:12Cratioa All 15.8 Argentina 17.2 Australia 19.4 Austria 22.0 Brazil 11.1 Canada 21.6 China 13.9 England 25.4 France 21.8 Germany 21.7 Hungary 22.0 Indonesia 19.5

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Israel Japan Malaysia Mexico Netherlands Paraguay Portugal Scotland Slovakia SouthAfrica Spain Sweden Turkey UnitedStates Uruguay

20.4 11.8 21.5 13.9 20.7 12.1 20.7 25.2 21.0 13.0 21.1 23.2 20.5 14.5 16.7

aMeasuredinpartspermillionatoms(×100).

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QUESTIONS▶ 1. Dotheaveragelocalratiosdifferfromthe26-countryaverageratio?Whatstatisticaltes wouldyouperformtoshowthatthedifferencesbetweentheindividualcountryaverages andtheall-countriesaveragearesignificant?(RefertoAppendixB.) 2. Thecountriesfromwhichthehamburgerswereanalyzedareindifferentlocationson Earth.Onewaytocomparelocationsisbygeographiclatitude.Youmayrecallthatin latitude,0degreesdefinestheequatorand90degreesdefinesthepoles.TableBshows average13C:12CratiosofBigMacbeefpattiesfromdifferentlatitudes.Plotthedataon agraphofratioversuslatitude.Whatcanyouconcludefromthesedata? TableB 13C:12Cratioa

Latitude 20°S–20°N 20°–40°b

11.4 15.3

40°–60°b

21.8

aAveragevaluemeasuredinpartspermillionatoms(×100). b20°S–40°Sand20°N–40°N;40°S–60°Sand40°N–60°N.

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

GotoAchieveforacompanionDatainDepthexercise. Anelement’satomicweight(orrelativeatomicmass)isequivalenttotheaverageofthemass numbersofarepresentativesampleofatomsofthatelement,withalltheisotopesintheir normallyoccurringproportions.Moreprecisely,anelement’satomicweightisdefinedasthe ratiooftheaveragemassperatomoftheelementto1/12ofthemassofanatomof12C. Becauseitisaratio,atomicweightisadimensionlessphysicalquantity—itisnotexpressed inunits.Theatomicweightofhydrogen,takingintoaccountallofitsisotopesandtheir typicalabundances,is1.00794.Thisnumberisfractionalbecauseitistheaverageofthe contributingmassesofalloftheisotopes.Thisdefinitionimpliesthatinanygivensampleof hydrogenatomsofaparticularelementfoundonEarth,theaveragecompositionofisotopes willbeconstant.Butasyousawintheopeningtothischapter,thatisnotnecessarilyso. SomewaterhasmoreoftheheavyOisotopes.Sochemistsarenowlistingatomicweightsas ranges,forexample,H:1.00784–1.00811.

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Mostisotopesarestable.However,some,calledradioisotopes,areunstableand spontaneouslygiveoffenergyintheformofα(alpha),β(beta),orγ(gamma)radiationfrom thenucleus.Knownasradioactivedecay,thisreleaseofenergytransformstheoriginalatom Thetypeoftransformationvariesdependingontheradioisotope,butsometransformations resultinadifferentnumberofprotons,sothattheoriginalatombecomesadifferentelement. Thisisespeciallytrueofelementswithatomicnumbersgreaterthan92,whichexistonlyin thelaboratory. Scientistscandetectreleasedradiationfromradioisotopes.Forinstance,ifyoufeedan earthwormfoodcontainingaradioisotope,youcanfollowtheworm’spaththroughthesoil byusingadetectorcalledaGeigercounter.Mostatomsinlivingorganismsareorganized intostableassociationscalledmolecules.Ifaradioisotopeisincorporatedintoamolecule,it actsasatagorlabel,allowingaresearcherorphysiciantotrackthemoleculeinan experimentorinthebody(Figure2.4).

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Copyright © 2020. Macmillan Learning. All rights reserved. Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

aresixcolumnsineachrow.Acalloutatthetopofthefirstcolumnreads,“Atomsinthe samecolumnhavethesamenumberofelectronsintheouter(valence)shellandhavesimilar chemicalproperties.”Acalloutatthetopofthethirdcolumnreads,“Electronsoccupyingthe sameorbitalareshownaspairs.”Theatomsineachrowareasfollows,with“none” indicatingablank(noatom) Firstelectronshell:Hydrogen(H)none,none,none,none,Helium(He) Secondelectronshell:Lithium(Li),Carbon(C),Nitrogen(N),Oxygen(O),Fluorine(F), Neon(Ne) Thirdelectronshell:Sodium(Na),none,Phosphorus(P),Sulfur(S)Chlorine(Cl)Argon(Ar) Acalloutatthebottomencompassesthefirst5ofthe6columnsandreads,“Atomswhose outermostshellscontainunfilledorbitals(unpairedelectrons)arereactive.”Theseinclude Hydrogen,Lithium,andSodium(column1,1unpairedelectroninoutershell);Carbon (column2;4unpairedelectronsinoutershell);NitrogenandPhosphorus(column3;4paired and1unpairedelectronsinoutershell;OxygenandSulfur(4pairedand2unpairedelectrons inoutershell);FluorineandChloriine(3pairedand1unpairedelectronsinoutershell). Acalloutatthebottomofthesixthcolumnreads,“Whenalltheorbitalsintheoutermost shellarefilled,theatomisstable”andidentifiesHelium(2pairedelectronsinoutershell) andNeonandArgon(8pairedelectronsinoutershell.) Q:

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1. Whichelementsonthisgraphdonotreactwithotherelements?Why? Atomswithunpairedelectrons(i.e.,partiallyfilledorbitals)intheiroutermostelectronshell areunstableandwillundergoreactionsinordertofilltheiroutermostshell.Reactiveatoms canattainstabilityeitherbysharingelectronswithotheratomsorbylosingorgainingone ormoreelectrons.Ineithercase,theatomsinvolvedarebondedtogetherintostable associationscalledmolecules.Thetendencyofatomstoformstablemoleculessothatthey haveeightelectronsintheiroutermostshellisknownastheoctetrule.Manyatomsin biologicallyimportantmolecules—forexample,carbon(C)andnitrogen(N)—followthis rule.Animportantexceptionishydrogen(H),whichattainsstabilitywhentwoelectrons occupyitssingleshell(consistingofjustonesorbital). KEYCONCEPT2.1RecapandAssess

Hillis, D., Heller, H. C., Hacker, S. D., Hall, D., Sadava, D., & Laskowski, M. (2020). Life : The science of biology. ProQuest Ebook Central http://ebookcentral.proquest.com Created from unimelb on 2021-02-28 20:18:50

Livingorganismsarecomposedofthesamesetofchemicalelementsastherestofthe universe.Anatomconsistsofanucleusofprotonsandneutronsandacharacteristic configurationofelectronsinorbitalsaroundthenucleus.Anatom’schemicalpropertiesare determinedbyitsatomicstructure.Elementsarecomposedofatomswiththesamenumber ofprotons.Elementsaregroupedintheperiodictableaccordingtothenumberofelectronsin theiroutermostshell. 1. Describehowtheconfigurationofthevalenceshellinfluencestheplacementofan elementintheperiodictable. 2. Howdoesbondinghelpareactiveatomachievestability? 3. WouldyouexpecttheelementalcompositionofEarth’scrusttobethesameasthatof thehumanbody?Explainyouranswer. 4. Thereisanisotopeofoxygenwithamassnumbe...