Chapter1Answers
SectionReviewQuestions
1.1Evolutionaryrelationshipsareideallyreflectedintaxonomy.Closelyrelatedanimalsshare taxonomicclassificationcategories.TheserelationshipsareultimatelybasedonsharedDNA. OrganismsthataremorecloselyrelatedhavemoreDNAincommon.Sincemostmorphological characteristicsaregeneticallybased,whentaxonomistsstudymorphologytheyarestudying geneticrelationships.BothDNAandmorphologycanbeusedinestablishingtaxonomic relationships.
1.2Therearemanyexamples.Oneexampleistheintroductionofthezebramussel(Dreissena polymorpha)intotheUnitedStatesinthe1980’s,probablybeingcarriedhereintheballastwater ofshipscomingfromEurope.ThezebramusselisasmallbivalvenativetosoutheastRussia.It livesasafilterfeederattachedtofirmsubstratesbystrongprotein(byssal)threads.Inthe UnitedStatesthezebramusselhasbecomeaseriousthreattonativemusselsasitout-competes nativemusselsforfoodandsubstrate.Thezebramusselwilloftenusetheshellsofother musselsassubstrateforattachment,killingthenativemussel.Theyalsoclogfactorycooling intakepipes.TheseinvadersfirstappearedintheGreatLakesin1988andhavespread throughouttheGreatLakesandintotheMississippiRiverdrainage. ConceptReviewQuestions
1.Biologyisthestudyoflife.Zoologyisthestudyofoneofthemajorkingdomsoflife,the Animalia.Inadditiontoevolutionandecology,alllife(thusbiologyandzoology)isunitedby commongeneticmolecules(DNAandRNA),andacommonunitoforganizationthecell.
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2.Currentissuesthatinvolvebothzoologyandquestionsofethicsandpublicpolicyarefar reaching.Theseissuesincludespeciespreservation,habitatdestruction,humanpopulation growth,theteachingofevolutioninpublicschools,animalrights,andmanyothers.Zoologists areunitedasscientists.Zoologistscaninformpublicpolicydebatesbyprovidingaccurate informationonanimals,theenvironment,evolutionaryprocesses,andmanyothertopics. Zoologistshavearesponsibilitytoconveyinformationandapplicationstrategiesasclearlyand asaccuratelyaspossibletothepublicandpublicinstitutions.Atthesametime,zoologistsarea diversegroupofscientistswithdifferentworldviews.Wecanexpectdifferencesofopinion amongzoologistsinthelightofinsufficientdataanddifferingworldviews.
3.Somesolutionstoenvironmentalproblemsseemsimplerthantheyreallyarebecausemostof usliveincountrieswherethestandardoflivingmakesecologicalchoiceseithereasyoratleast notamatterofimmanentlifeordeath.Inmanylessdevelopedcountries,day-to-daysurvival choicesarenotnecessarilyecologicallyminded.Culturesthathavebeensustainedbyhunting speciesthatarenowendangeredorclearingtropicalforestsforagriculturalusewillnotchange simplybecausezoologistsindevelopedcountriestellthemtheyneedtochange.Partnership withlessdevelopedcountriescanshowhowpreservationwillprovideresourcesthatwillbenefit thesecountries.
4.ThestoryofcichlidsinLakeVictoriadocumentshowissuesofday-to-daysurvivalinless developedcountriescanleadtowide-rangingenvironmentaldegradation.Itemphasizesthe interconnectednatureofecologicalsystemsandhowdisturbingthesesystemscanhave consequencesthataremoreseverethantheoriginalproblem.Wecanalllearnfromthisaccount andnotrepeatitinthefuture.
Chapter2Answers
SectionsReviewQuestions
2.1SomesimilaritiesbetweeneukaryoticandprokaryoticcellsofEubacteriaandArchaea includethefollowing:1)theyarecomprisedofsinglecellsthatlackamembrane-boundnucleus andextensivecytoplasmicorganelles,2)theybothhaveacellwall,3)vacuolesandvesiclesmay bepresent.
2.2Thevolumewillincreaseby1000times.Remember,acell’ssurfaceareamustbelarge enoughtomeetthemetabolicneedsofitsvolume.
2.3Ifjustasinglelayerofphospholipidswerepresent,thecellwouldnotbeabletoregulateits contentsandwhatmovesintooroutofthecell.Sinceproteinsarenotpresent,itwouldnot functionasaselectivelypermeablemembranetocontrolthepassageofspecificmolecules.
2.4TheconcentrationoftheIVsolutionneedstobeisotonicwithyourredbloodcells.Ifitwere excessivelyhypotonic,waterwouldmoveinandtheRBSswouldburst(hemolyze);ifitwere hypertonic,yourredbloodcellswouldlosewaterandshrinkorcrenate.
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2.5Nuclearpores,vaults,ribosomes,andtheERareallstructuresinvolvedinintracellular transport.
2.6Poresallowtheexchangeofsmallmoleculesbetweenthecytoplasmandnucleoplasm.
2.7Mostorgansaremadeupofmultipletissuetypes.Forexample,theheartcontainscardiac muscle,nervoustissue,connectivetissue,andepithelialtissue.
2.8Bloodisatypeofconnectivetissuebecauseitcontainsalotofextracellularmaterialinthe formofplasmaanditisderivedfrombonemarrowaconnectivetissue.
2.9Theskinisthelargestorganinamammal.
2.10.Yes,theorgansystemscanoverlap.Considerthecirculatoryandrespiratorysystemsbeing dependentoneachotherinordertomaintainhomeostasis.
ConceptReviewQuestions
AnalysisandApplicationQuestions
1.Themitochondrioniscalledthe“powergenerator”ofthecellsincethisiswherethe energymolecule,ATP,isproduced.ATPpowersallenergyrequiringprocessesinthe cell.
2.Theplasmamembraneregulatesthepassageofmoleculesintoandoutofthecell.The conceptof“membranebiology”impliesthiscommonfunction.Thiscommonalityisdue totheselectivepermeability,meaningthatcertainsubstancescanfreelypassthroughthe membrane,somearetransportedacross,andothersareprohibitedfromeitherenteringor leaving.Inadditiontheproteinsembeddedwithintheplasmamembranehavevaried commonfunctionssuchaschannelproteins,transportproteins,cellrecognitionproteins, receptorproteins,enzymaticproteins,andjunctionproteins.
3.The“fluid-mosaicmodel”statesthattheproteinmoleculesembeddedinthemembrane haveapattern(amosaic)withinthephospholipidbilayer.Theproteinpatternvarieswith thetypeofcellandwithinthesamemembraneatdifferenttimes.Cholesterolmolecules presentintheplasmamembraneofeukaryoticcells,lendsupporttothemembrane, givingitthegeneralconsistencyoffluidoliveoil.
4.Anosmoticgradientiscreatedwhentherearemoresolutemoleculesononesideofa membranecomparedtotheotherside;conversely,therearemorewatermoleculesonthe sidewithfewersolutemolecules.
5.Someanimalcellscantransportmoleculesagainstaconcentrationgradientbyusing energytomovemoleculesacrosstheplasmamembranetowardahigherconcentrationof solutemolecules.Notethatthetransportproteinwillchangeshapeduringtheprocess.
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Someinvertebrates,suchasaprotozoan,cansurvivewithoutthisprocessbutitisa necessityinallhigheranimals.
Chapter3Answers
SectionReviewQuestions
3.1Eukaryoticorganismshavemuchmorechromatinthandoprokaryoticorganisms.DNAof thelatterisusuallycircularinformandhistoneproteinsarenotpresentorusedinDNA packaging.Inaddition,prokaryoteshavemanyfewergenes.Forexample,thecommon bacteriumEscherichiacolihasjustover4,000genes.Humanshaveabout20,000protein-coding genes,andmuchmoreDNAthatisnoncoding.Theuseofhistoneproteinsinchromatin condensationisuniquetoeukaryotesandisapparentlyrequiredtofacilitatethedistributionof largeamountsofDNAduringcelldivisionprocesses.
3.2Mitoticcelldivisionresultsindaughtercellsthataregeneticallyidenticaltotheparental cell.Thismeansthata2Ncellundergoingmitoticcelldivisionproduces2Ndaughtercells.If thesedaughtercellswerespermoreggcells,fertilizationwouldresultin4Nzygoteswiththe numberofchromosomesetsdoublingwitheverygeneration.Inaddition,mitoticcelldivision doesnotpromotevariability,whichissoveryimportantforsexualreproduction.(Seethe answerto3.3below.)
3.3Meioticcelldivisionaccomplishestwothingsthataresoveryimportantintheformationof gametes:thereductioninthechromosomenumberfrom2Nto1Nandtheintroductionof variationintotheproductsofmeiosis.Thereductionofchromosomenumberoccursafter homologouspairsundergosynapsisduringprophaseI,lineupattheequatorofthecellin metaphaseI,andsegregatetooppositepolesofthecellinanaphaseI.Thecellsproducedinthe firstmeioticdivisionthuscontainonememberofeachhomologouspairofchromosomesandare 1N.SimilarlythecrossingovereventsofprophaseIandtheindependentassortmentof homologouschromosomesofanaphaseIarethereasonswhycellsproducedfrommeiosisofa parentcellaregeneticallydifferent.Thesecondmeioticdivisionofadaughtercellisjustlike mitoticcelldivisionanddoesnotchangechromosomenumbersorintroducenewgenetic variationintothedaughtercells.
3.4Thesecondstrandwouldbe5’TCACGTAAG3’ ThemessengerRNAwouldbe5’UCACGUAAG3’ Theaminoacidsequencewouldbeserine-arginine-lysine(seetable3.11)
3.5Segregationistheseparationofgenesonhomologouschromosomesintoseparategametes andthisoccursduringanaphaseI.Independentassortmentistherandomdistributionof
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nonhomologouschromosomesintoseparategametes.Thisrandomdistributionininfluencedby howchromosomesinsynapsislineupduringmetaphaseIandtheirseparationduringanaphaseI.
ConceptReviewQuestions
1.c.
2.c.
3.g.
4.d.
5.b.
AnalysisandApplicationQuestions
1.Thesimilaritiesofthestagesofmeiosisandmitosishaveledcellbiologiststotheconclusion thatthetwoprocessesshareanevolutionaryhistory.Theevolutionaryeventsinthiscommon historyareunderinvestigation.Mitosisisbelievedtobetheolderofthetwoprocesses.Itis firstseeninprotistsandprimitivefungi,someofwhichhaveaclosedmitosisinwhichall chromosomaleventsoccurwithoutthedissolutionofthenuclearmembrane.Openmitosis,with thedissolutionofthenuclearenvelope,maybealaterevolutionarydevelopment.Meioticcell divisioninvolvestheuseofmanygenesthatalsocontrolmitoticcelldivision.Obviously,the complexproteinsassociatedwithcarryingoutandcontrollingsomeaspectsofmeiosis synapsis,crossingover,andindependentassortmentareuniquetothisformofcelldivisionand cameaboutlaterinevolution.
2.Bothchromatidsofonechromosomewouldtraveltogethertothesamepoleofthecell.One daughtercellwouldhave5chromosomesandtheotherdaughtercellwouldendupwith7 chromosomes.Changesinchromosomenumberliketheseareusuallydetrimentaltothecell.
3.Thegeneticmaterialforthedevelopmentandfunctionofanentireorganismiscarriedbythe DNAofeverycell,exceptforgametes.Allcells,however,donotexpressallgenes.Stomach cellsaredifferentinformandfunctionfromskincells,andcellsthatformsperminthetestesof amalearenotfullyfunctioninguntilsexualmaturity.Inordertoaccountfordifferencesincell typesanddifferencesinorganismsduringdifferentlifestagesonemustlooktocomplexgenetic controlsystemsthatturnsomegenesonandsomegenesoffindifferentcellsandatdifferent stagesindevelopment.
4.Genescarriedbythesamechromosomearesaidtobe“linked.”Twogenesveryneareach otheronthesamechromosometendtobecarriedtogethertothesamepoleofthecellduring anaphaseIofmeiosis,thustheydonotsegregateindependently.Ontheotherhand,genesthat
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arefarapartonthesamechromosomeundergocrossingoverfrequentlyenoughthatthesegenes dosegregateindependentlyeventhoughtheentirechromosomesonwhichtheyresidedonot.
Chapter4Answers
SectionReviewQuestions
4.1Lamarck’sideaofevolutionarychangewasbasedontheideathatcharacteristicsare acquiredbyorganismsastheenvironmentchangedandanewneedarose,forexamplelonger necksingiraffeswouldhavearisenastheyneededtoreachhigherintotrees.Ifthisideawas true,extinctionwouldbelesslikelybecauseeveryenvironmentalchallengewouldbemetbya changethatwouldpermitsurvival.Clearly,thisisnotthecaseasextinctionhasbeenthefatefor mostspeciesthathavelivedonplanetEarth.
4.2DarwingrewupinruralEnglandwherehisinterestscenteredaroundcollectingandhunting. Darwinhadparentswhoinsistedthathereceiveauniversityeducation.Darwinhadclose relationshipswithCambridgescientistswhoencouragedhisloveofnature.
4.3Adaptiveradiationistheformationofmultipleformsfromoneancestorasaresultofthe openingofnewhabitats.ThefirstfinchpopulationsontheGalapagosIslandsencountered environmentsthatweredevoidofpredatorsandhadfewotherbirdsoccupyingthediverse habitatsavailableontheislands.Fincheswithbillandothervariationsthatallowedthemto exploittheseavailablehabitatspassedtheirvariationsontooffspring.Eventuallymanybird habitatswereoccupiedbythe14speciesoffinchesseentoday,eachwithdistinctiveadaptations notseeninmainlandfinches.
4.4Naturalselectionoccursasaresulttraitsbeingselectedagainstor“weededout”ofa population.Theresultofthis“weedingout”isthatadaptivetraitsaremorelikelytobepassed ontoafuturegeneration.Thesetraitsthatarebeingpassedintofuturegenerationsareoften thoughtofasbeingselectedfor,althoughthesectionforthesetraitsisindirect.Selectingfor adaptivevariationsdoesnotmeanthatnaturalselectionpicks“good”variationsoutofa “variationpool”andpromotestheirperpetuation.Thiskindofthinkingaboutnaturalselection asapositiveforcecanleadtoerroneousteleologicalideas,whereevolutionisrepresentedas occurringinresponsetoneeds.
4.5Laboratory,orexperimental,scienceisjustonemethodinscience.Sciencealsouses observationalandhistoricalmethods.Theselatterapproachestoscienceusefieldobservations andhistoricaldatatodocumentandexplainnaturalphenomena.Thesearethesamemethods thatareused,forexample,inforensicsciencetoreconstructeventsatthesceneofacrime.We aresoveryconfidentintheuseofthiskindofsciencethatindividualsaregivenveryharsh sentencesbasedonthisscience.Inthesameway,biogeography,paleontology,andconceptsof homologyandanalogypresentconvincingevidenceofevolution.Virtuallyallscientistsare
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