精讀團(tuán)期題錄屏篇閱讀真題

4.Theword

meaningtoA.firstB.possiblyC.sometimes

D.Reluctantly

“initially”

in

the

passage

is

closet

in

Amoreconservativestrategywastoplantcropsonly

inareaswithreliablespringsandgroundwatertables.ThatwasthesolutioninitiallyadoptedbytheMimbresandbypeopleinthephaseknownasPueblo

II.However,itthenbecamedangerouslytemptingtoexpandagricultureduringwetdecadeswithfavorablegrowingconditionsintomarginalareaswithlessreliablespringsandgroundwater.Thepopulationmultiplyinginthosemarginalareasmightthenfinditselfunabletogrowcropsandmightstarvewhentheunpredictableclimateturneddryagain.ThatfateactuallybefelltheMimbres,whostartedbyfarmingthefloodplainandthenbegantofarmadjacentlandabovethefloodplainastheirpopulationcametoexceedthefloodplain’scapacitytosupportit.Theygotawaywiththeirgambleduringawetclimatephase,whentheywereabletoobtainhalftheirfoodoutsidethefloodplain.However,whendroughtconditionsreturned,thatgambleleftthemwithapopulationdoublewhatthefloodplaincouldsupport,and

Mimbressocietycollapsedsuddenlyunderthestress.

5.Theword“adjacent”

meaningtoA.neighboringB.higherC.unused

D.additional

in

the

passage

is

closet

in

6.Accordingtoparagraph3,whichofthe

following

wasthecauseofthecollapseoftheMimbressociety?

Theycouldnotovercomethestressofmovingtoanewareawitheachchangeintheclimate.

Thefloodingoftheirfarmlandduringawetclimatephasepreventedthemfromgrowingenoughtofeedtheirpopulation.

Adeclineinpopulationduringdryperiodspreventedthemfromexpandingtheirfarmingintonearbyareas.

Theirpopulationbecametoolargetosurvivewhen

theclimateenteredadryperiod.

Stillanothersolutionwastooccupyanareaonlyfora

fewdecades,untilthearea’ssoilbecameexhausted,thentomovetoanotherarea.Thatmethodworkedwhenpeoplewerelivingatlowpopulationdensities,whenthereweremanyunoccupiedareastomoveto,andwheneachoccupiedareacouldbeleftunoccupiedagainforsufficientlylongafteroccupationsothatitsvegetationandsoilnutrientshadtimetorecover.However,themethodofshiftingsitesafterashortoccupationbecameimpossibleathighpopulationdensities,whenpeoplefilledupthewholelandscapeandtherewasnowhereleftemptytomove

to.

7.Accordingtoparagraph4,thesolutionofmovingto

other,previouslyoccupiedareaswaseffectiveonlywhen

A.thesoilonthepreviouslyoccupiedlandhadbeenusedforfarmingatleastonceB.thevegetationand

nutrientsofthepreviouslyoccupiedareahadtimeto

recoverC.thereoccupations

timeD.thereoccupiedareas

populated

didnotlast

becamemore

along

densely

4

8.Thesolutionforunpredictablerainfalldescribedin

paragraph5involvedallofthefollowingEXCEPTA.plantingcropsinmanydifferentplaces,regardlessofpredictedrainfall

usingasimplepoliticalandsocialsystemforthecoordinationofagriculturalactivities

harvestingcropsfromthosesitesthatdidreceiveadequaterain

sharingharvestedcropswithpeoplewhosecrops

didnotgrowwell

Onemorestrategywastoplantcropsatmanysites

eventhoughrainfallwaslocallyunpredictableandthentoharvestcropsatwhicheversitesdidgetenoughraintoproduceagoodharvestandtoredistributesomeoftheharvesttothepeoplestilllivingatallthesitesthatdidnothappentoreceiveenoughrainthatyear.Butredistributionwasnotwithoutrisksbecauseitinvolvedacomplexpoliticalandsocialsystemtointegrateactivitiesbetweendifferentsites,sowhenthatcomplexsystemcollapsed,

lotsofpeopleendedupstarving.

9.Theword“dependable”inthepassageisclosetin

meaningtoA.adequateB.familiarC.reliable

D.plentiful

10.Whichofthefollowingcontributedtothesuccess

ofthestrategydiscussedinparagraph6?

Cropswereplantedhighenoughtoavoidbeingcarriedawaybyfloods.

Cropswereplantedwhereverthereweresourcesofwater,regardlessoftheirproximitytowherepeopleactuallylived.

Farmingwaslimitedtoecologicalzonesthatweresimilartoeachother.

Insteadofaimingatbecomingself-sufficient,eachvillagebecamepartofanetworkofdiverseeconomic

activities.

Theremainingstrategywastoplantcropsandlive

nearpermanentordependablesourcesofwater,butonlandscapebenchesabovethemainfloodways,soastoavoidtheriskofaheavyfloodwashingoutfieldsandvillages,andtopracticeadiverseeconomy,exploitingecologicallydiversezonessothateachsettlementwouldbeself-sufficient.Thatsolution,adoptedbypeoplewhosedescendentslivetodayintheSouthwest’sHopiandZunivillages,hassucceeded

formorethanathousandyears.

5

Whichofthefollowingbestdescribestheorganizationofthepassage?

AhistoricalaccountofthevariouspeoplethathavelivedinsouthwesternNorthAmericafollowedbyconflictingviewsabouttheaccuracyoftheaccount

AcomparisonandcontrastofthehistoricalroleofagricultureindifferentpartsofthesouthwesternregionofNorthAmerica

AnexplanationofhowthesolutionsdevelopedtoimprovelivingconditionsinsouthwesternNorthAmericaspreadtootherneighboringregions

Adescriptionofalong-standingproblemfacedbythepeopleinsouthwesternNorthAmericafollowedbya

discussiononstrategiesthathavebeenusedtoovercometheproblem

12.Lookatthefoursquares[■]thatindicatewherethefollowingsentencecanbeaddedtothepassage.

Anotherriskofirrigationwasthatfloodscouldsimplywashawaythedamsandchannels,asindeedmayhavehappenedeventuallytotheHohokam.

13.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.Completethe

summarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageor

areminorideasinthepassage.Thisquestionisworth2points.

PeopletryingtogrowcropsinthedrysouthwesternareaofNorthAmericaexperimentedwithvariousstrategies

foralmostathousandyears.

Experimentsinagriculturesucceededinthoseareasthatexperiencedclimatechangesthatincreasedtheamountofrainfallgraduallyovermanycenturies.

Inspiteofusuallydryconditions,waterrunofffromrainstormswasusedbytheHohokamtofloodfieldsanddeepenchannelsinirrigationsystems.

Shiftingsitesorplantinginareaswithgoodsourcesofwaterwassuccessfulonlyinareaswithlowpopulationdensities.

Farmingathigherelevationsmeantriskingfailurefromcoldweather,whileextensiveirrigationatthelowerelevationsriskeddestructivefloodsfromsuddenrainstorms.

Farmingindryclimatephaseswassuccessfulonlyathigherelevations.

Sharingfoodproducedatdifferentsiteshadlimitedsuccess,whileself-sufficientandecologicallysoundfarming

continuedtosucceed.

6

P2Earlylife-formsandEarth’sAtmosphere

1.Theword”altered”

meaningtoA.transformedB.protectedC.madeuseof

D.adaptedto

in

the

passage

is

closet

in

WhyhaslifeflourishedonEarth?Thisquestionhasa

two-partanswer.First,EarthhasbeenacradleforlifebecauseofitspositionrelativetotheSun.second,oncelifebeganonEarth,simpleearlylife-forms(photosyntheticbacteria)slowlybutinexorablyalteredtheenvironmentinamannerthatnotonlymaintainedlifebutalsopavedthewayforlater,complexlife-forms.Thesechangesallowedlater

organismstoevolveandthrive.Humansandother

2.Paragraph1

inferences?

supports

whichofthe

following

AftercomplexlifeformsaroseonEarth,bacteria

quicklyevolvedinordertomaintainfavorableconditionsforlife.

EarlylifeformsonEartharosefromtheprocessofphotosynthesis.

ThedevelopmentofcomplexlifeonEarthdependedonthepresenceofbacteriathatcouldbeconsumedbylargerorganisms.

ComplexlifeformsonEarthmaynothaveevolvedifEarthhadbeenfartherfromorclosertotheSun.

higher

organisms

owe

their life-supporting

environmenttotheseearlylife-forms.

3.Theword”emitted”

meaningtoA.disappearingB.examinedC.released

D.taken

in

the

passage

is

closet

in

Earth’searliestatmospherecontainedseveralgases:

hydrogen,watervapor,ammonia,nitrogen,methane,andcarbondioxide,butnooxygen.Gasmixturesemittedfrompresent-dayvolcanoesresemblethisearlyatmosphere,suggestingitsoriginfromvolcaniceruptions.InEarth’searliestatmosphere,methaneandcarbondioxideoccurredatmuchhigherlevelsthanatpresent—acircumstancethatwasfavorableforearlylife.Methaneandcarbondioxidearegreenhousegasesthatwarmatmospheresbyretardinglossofheattospace.ThesetwogaseskeptEarthwarmduringtheSun’searlyhistory,whentheSundidnotburnasbrightlyasitnowdoes.(Anearlydimperiod,withlaterbrightening,isnormalforstars

ofourSun’stype.)

4.Theword

meaningtoA.regulatingB.slowingC.restoring

D.directing

”retarding”

in

the

passage

is

closet

in

7

Inparagraph2,whydoestheauthorprovidethe

informationthatmethaneandcarbondioxidekepttheEarthwarmduringtheSun’searlyhistory?

ToexplainhowtheearlyEarthandtheearlySunwererelated

Tosupporttheclaimthatmethaneandcarbondioxidearegreenhousegases

ToexplainwhythehighlevelsofmethaneandcarbondioxideinEarth’searlyatmospherewerefavorableforearlylife

Tosuggestthatthesegasesaffecthowbrightlythe

Sunburns

Paragraph2supportswhichofthefollowing

statementsaboutmethaneandcarbondioxidepresentinEarth’searliestatmosphere?

TheysloweddownthelossofheatfromEarth’satmosphere.

Theycausedthesunlighttobelessbrightthanitcurrentlyis.

Theyoccurredinsmalleramountsthantheycurrentlydo.

Theypreventedthedevelopmentofearlylife-forms.

7.Theword

meaningtoA.pureB.balancedC.plentiful

D.warm

”abundant”

inthe

passage

is

closet

in

Earth’smodernatmosphere,whichis78percent

nitrogengas,21percentoxygen,andabout1percentargon,watervapor,ozone,andcarbondioxide,differsdramaticallyfromtheearliestatmospherejustdescribed.ThemodernatmospheresupportsmanyformsofcomplexlifethatwouldnothavebeenabletoexistinEarth’sfirstatmospherebecausetheoxygenlevelwastoolow.Also,ifatmosphericmethaneandcarbondioxidewereasabundantnowastheywereinEarth’searliestatmosphere,theplanet’stemperaturewouldlikelybetoohotformostspecieslivingtoday.

Howandwhendidtheatmospherechange?

8.According

toparagraph2and3,whichofthe

followingisonewayinwhichEarth’searlyatmosphere

differedfromitscurrentatmosphere?

Ithadfewergreenhousegases.

Itwaswarmer.

Ithadlowerlevelsofcarbondioxide.

Itdidnotcontainmethane.

8

9.Theword

meaningtoA.changeB.generateC.destroy

D.support

”sustain”

in

the

passage

is

closet

in

Theanswertothisriddleliesinthemetabolicactivity

ofearlyphotosyntheticlife-formsthatslowlybutsurelytransformedthechemicalcompositionofEarth’s

atmosphere.Someoftheseearlyorganisms

were

photosynthetic

relatives

of

modern

cyanobacteria(blue-greenbacteria).Intheprocessof

photosynthesis,carbondioxidegascombinedwithwateryieldsoxygen.InEarth’searlydays,allovertheplanetcountlessphotosyntheticbacteriaperformedphotosynthesis.Together,theseancientbacteriaremovedmassiveamountsofcarbondioxidefromEarth’satmospherebyconvertingittosolidorganiccarbon.Theseancientbacteriaalsoreleasedhugequantitiesofoxygenintotheatmosphere.Otherancientbacteriaconsumedmethane,greatlyreducingitsamountintheatmosphere.WhenourSunlaterbecamehotter,thecontinuedremovalofatmosphericcarbondioxideandmethanebyearlybacteriakeptEarth’sclimatefrombecomingtoohottosustainlife.Moderncyanobacteriastillprovidethesevaluable

servicestoday.

10.Accordingtoparagraph4,ancientbacteriachanged

thechemicalcompositionofEarth’satmospherebyperformingallofthefollowingactivitiesEXCEPTA.raisingthetemperatureoftheatmosphere

B.removingmethaneandcarbondioxide

C.creatingorganiccarbonD.producingoxygen

11.Itcanbeinferredfrom

paragraph

5that

early

Thebacterialoxygenreleaseimprovedconditionsfor

lifeintwoways.First,oxygenisessentialforthemetabolicprocessknownascellrespirationthatallowscellstoefficientlyharvestenergyfromorganicfood.Second,oxygenintheupperatmospherereactstoformaprotectiveshieldofozone.■Earthis

constantlybombardedbyharmfulultraviolet(UV)

life-formsonEarthwereconfinedto

because

theoceans

thethickozonelayeratthetimewouldhavemadeit

difficultforthemtosurviveonland

waterwastheonlyavailableprotectiontheyhadagainstultravioletradiation

landprovidedthemwithonlylimitedamountsofwaterneededforsurvival

theirmetabolicsystemswereinefficient

Sun. ■Today,

radiation

from

the

Earth’s

upper-atmosphereozoneshieldabsorbsenoughUVto

allowdiverseformsoflifetosurvive.■ButbecauseearlyEarthlackedoxygeninitsatmosphere,italsolackedaprotectiveozonebarrier.■Asaresult,earlylifeonEarthwasconfinedtotheoceans,wherethewaterabsorbedtheUVradiation.Onlyafteroxygenreleasedbyancientbacteriadriftedupintotheupperatmosphereandreactedwithotheroxygenmoleculestoformaprotectivelayerofozonecouldlifeflourishatthesurfaceandontheland.TheabsenceofanoxygenatmosphereonMarsandotherplanetsinoursolarsystemmeansthattheseplanetsalsolackan

A.Anylifeformsthatmayhaveexistedonother

12.Whichofthesentencesbelowbestexpressesthe

essentialinformationinthehighlightedsentenceinthepassage?Incorrectchoiceschangethemeaningin

importantwaysorleaveoutessentialinformation.

9

planetsprobablyweredestroyedbyUVradiation.

B.OtherplanetsinoursolarsystemlacktheoxygenatmospherethathelpsexplainwhylifeexistsonEarth.C.TheabsenceofoxygenonotherplanetsmeansthatthoseplanetslackanozoneshieldtoprotectlifeformsagainstUVradiation.

D.LifeformscannotsurviveUVradiationwithoutthe

protectionofanozoneshield.

fromUVradiation.ThesurfaceofMarsisbombarded

withdeadlyradiation;ifanylifeexistsonMars,

wouldalmostcertainlybesubterranean.

it

ozoneshieldthatwouldprotectsurface-dwellinglife

13.Lookatthefoursquares[■]thatindicatewherethefollowingsentencecouldbeaddedtothepassage.

Wherewouldthesentencebestfit?Clickonasquare[■]toaddthesentencetothepassage.

Butprotectionagainstwhat?

14.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.Completethe

summarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageor

areminorideasinthepassage.Thisquestionisworth2points.

Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewText.

Earth’searliestatmospherewastransformedinwaysthatallowedthedevelopmentofcomplexlifeforms.

VolcanoeschangedEarth’searliestatmosphereinwaysthatallowedlifetodevelop,andbacteriathatusedoxygenproducedbyphotosynthesisfurtheralteredtheatmospheretowhatwefindtoday.

Whenthesunbecamebrighter,earlybacteriaremovedmethaneandcarbondioxidefromtheatmosphere,preventingEarthfrombecomingtoohotforlifetosurvive.

EarlybacteriaprovidedtheoxygenthatwasneededtosupportthemetabolismofcomplexlifeformsandtoformanozoneshieldagainstdeadlyUVradiation.

VolcaniccarbondioxideinEarth’searlyatmospherekeptEarthwarmenoughforlifetobeginduringthetimewhentheSunwastoodimtoprovidemuchwarmth.

EarthhasbeenabletosupportlifebecauseitspositionrelativetotheSunprovideditwithenoughheat,butnottoomuchheatforearlybacteriatoevolve.

ComplexlifeevolvedontheEarth’ssurface,butnotonMarsorotherplanetsinthesolarsystembecauseon

thoseplanets,earlysurfacelifewaskilledbyUVradiation.

10

P3ConstraintsonNaturalSelection

1.Whichofthesentencesbelowbestexpressesthe

essentialinformationinthehighlightedsentenceinthe

Naturalselectionistheprocessinwhichorganisms

withcertaintraitssurviveandreproducewhileorganismsthatarelessabletoadapttotheirenvironmentdieoff.AsDarwinpointedout,naturalselectiondoesnotnecessarilyproduceevolutionaryprogress,muchlessperfection.Thelimitstotheeffectivenessofnaturalselectionaremostclearlyrevealedbytheuniversalityofextinction.Morethan

99.9percentofallevolutionarylinesthatonceexistedonEarthhavebecomeextinct.Massextinctionsremindusforcefullythatevolutionisnotasteadyapproachtoanever-higherperfectionbutanunpredictableprocessinwhichthebest-adaptedorganismsmaybesuddenlyexterminatedbyacatastropheandtheirplacetakenbylineagesthatpriortothecatastropheseemedtobewithout

distinctionorprospects.

passage?Incorrectchoiceschangethemeaning

importantwaysorleaveoutessentialinformation.A.Evolutionisanunpredictableprocessbecause

in

in

mass extinctions highly-evolved organisms are

exterminated.

B.Evolutiondoesnotprogresssteadilytoever-higherlevelsofperfectionbecause,asshownbymassextinctions,lineagesfavoredbyevolutioncanbesuddenlyreplacedbythosenotfavoredpreviouslywhencircumstanceschange.

C.Catastrophesremindusthatevolutionisaprocessinwhichthebest-adaptedorganismsareexterminatedandtheirplacetakenbylineagesshowntobepoorly

adapted.

D.When

mass

extinctions exterminate

the

best-adaptedorganisms,lessimportantlineages

suddenlybecomebetteradaptedandtaketheirplace.

2.Accordingtoparagraph1,whichofthefollowing

providesevidencethatnaturalselectiondoesnotalwaysleadtoevolutionaryprogress?

A.MostevolutionarylinesthatonceexistedonEarthhavebecomeextinct.

B.Evolutionarylinesusuallyweakenastheyincreaseinage.

C.Thehistoryofevolutionshowsthatmanyevolutionarylinescanbecomeextinctatthesametime.

D.Sofar,lessthanonepercentofevolutionarylineshaveachievedsuchperfectadaptationtotheir

environmentthattheywillneverbecomeextinct.

11

3.Theword”remote”

meaningtoA.correspondingB.distantC.separate

D.direct

in

the

passage

is

closet

in

Therearenumerousconstraints,orlimits,onthe

powerofnaturalselectiontobringaboutchange.First,

the

genetic

variation

needed

to

perfect

a

characteristicmaynotbeforthcoming.Second,during

evolution,theadoptionofoneamongseveralpossiblesolutionstoanewenvironmentalopportunitymaygreatlyrestrictthepossibilitiesforsubsequentevolution.Forinstance,whenaselectiveadvantageforaskeletondevelopedamongtheancestorsofthevertebratesandthearthropods,theancestorsofthearthropodshadtheprerequisitesfordevelopinganexternalskeleton,andthoseofthevertebrateshadtheprerequisitesforacquiringaninternalskeleton.Theentiresubsequenthistoryofthesetwolargegroupsoforganismswasaffectedbythetwodifferentpathstakenbytheirremoteancestors.Thevertebrateswereabletodevelopsuchhugecreaturesasdinosaurs,elephants,andwhales.Alargecrabisthelargesttypethatthearthropodswereableto

achieve.

4.Inparagraph2,why

doestheauthordiscussthe

ancestorsofvertebratesandarthropods?

A.Toexplainhowasinglefeaturecan

extinctionofentiregroupsoforganisms

causethe

Toidentifysomefactorsthatdeterminehowlarge

anorganismcanbecome

Toillustratethepointthatearlierdevelopmentsinfluencethepossibilitiesforfuturedevelopment

Toemphasizetheroleoftheenvironmentinthe

developmentoforganisms

5.Whichofthefollowingcanbe

paragraph2aboutarthropods?A.Therearefewerofthemthan

vertebrates.

inferredfrom

thereareof

Theirancestorshadaselectiveadvantageoverthe

ancestorsofvertebrates.

Theirancestorsoncepossessedinternalskeletons.

Theirbodyfeaturespreventthemfrombecominglargeorganisms.

6.Theword”resistance”inthe

meaningtoA.oppositionB.pressureC.interaction

D.competition

passageisclosetin

Another

constraint

on

natural

selection

is

developmentalinteraction.Thedifferentcomponents

ofanindividualorganism—itsstructuresandorgans—arenotindependentofoneanother,andnoneofthemrespondstoselectionwithoutinteractingwiththeothers.Thewholedevelopmentalmachineryisasingleinteractingsystem.Organismsarecompromisesamongcompetingdemands.Howfaraparticularstructureororgancanrespondtotheforcesofselectiondepends,toaconsiderableextent,ontheresistanceofferedbyotherstructuresandorgans,aswellascomponentsofthegenotype(the

totalityofanindividual’sgenes).

7.Accordingto

paragraph3,whymustorganisms

compromisebetweencompetingdemands?

A.Aparticularorganorstructuremaybeunabletorespondtoselectionpressuresduetotheneedsof

otherpartsoftheorganism.

12

B.Anorganism’sabilitytorespondtotheforcesof

selectiondependsonthedemandsofotherorganismswithinitsenvironment.

C.Anorganism’senvironmentanditsgenotypetryatthesametimetoinfluenceitsabilitytorespondtonaturalselection.

D.Differentelementsoftheenvironmentcallforadaptationsthatareoftenincompatiblewithone

another.

Paragraph4supportsallofthestatementsabout

genesEXCEPT:

Ourunderstandingoftheextenttowhichgenesactindependentlyhaschangedovertime.

Genesareclassifiedintogroupsonthebasisoftheirfunction.

Somegenesseemtohavenofunction.

Studiestoidentifywaysthatgenesinteracthave

beenlargelysuccessful.

Thestructureofthegenotypeitselfimposeslimitson

thepowerofnaturalselection.Theclassicalmetaphorofthegenotypewasthatofabeadedstringonwhichthegeneswerelineduplikepearlsinanecklace.

Accordingtothisview,eachgenewasmoreorlessindependentoftheothers.■Notmuchisleftofthispreviouslyacceptedimage.■Itisnowknownthattherearedifferentfunctionalclassesofgenes,somechargedtoproducematerial,otherstoregulateit,andstillothersthatareapparentlynotfunctioningatall.

Therearesinglecodinggenes,moderatelyrepetitiveDNA,highlyrepetitiveDNA,andmanyotherkindsofDNA.Discoveringexactlyhowtheyallinteractwithoneanotherisstillaratherpoorlyunderstood

areaofgenetics.

9.Theword

meaningtoA.harmfulB.continuousC.strong

D.excessive

”adverse”

in

the

passage

is

closet

in

Afurtherconstraintonnaturalselectionisthe

capacityfornongeneticmodification.Themoreplastictheorganism’sbodycharacteristicsare(owingtodevelopmentalflexibility),themorethisreducestheforceofadverseselectionpressures.Plants,andparticularlymicroorganisms,haveafargreatercapacityforindividualmodificationthandoanimals.Naturalselectionisinvolvedeveninthisphenomenon,sincethecapacityfornongeneticadaptationisunderstrictgeneticcontrol.Whenapopulationshiftstoanewspecializedenvironment,geneswillbeselectedduringthefollowinggenerationsthatreinforceandmayeventuallylargelyreplacethecapacityfor

nongeneticadaptation.

13

dangerous

randomC.common

D.powerful

10.Whatpointdoesparagraph6makeaboutthe

individualsthatsurviveaparticularnaturaldisaster?A.Theywerethesmallnumberoforganismsthathappenedtobewell-adaptedtosurvivethatkindofnaturaldisaster.

Theirdescendantswilllikelybeshapedbynaturalselectiontoevolvegenesthatwillmakethemfittosurvivethenextnaturaldisaster.

Theirsurvivalmayhavebeenduetochance,butfitnessalsocontributestotheirsurvivalovertime.

Theywillprobablyhavecomparativelyweak

offspringbecausethenaturaldisastereliminatedthe

individuals

combinations.

that

had

more

favorable gene

Finally,whichorganismssurviveandreproduceina

populationispartlytheresultofchance,andthisalsolimitsthepowerofnaturalselection.Chanceoperatesateveryleveloftheprocessofreproduction,fromthetransmissionofparentalchromosomestothesurvivalofthenewlyformedindividual.Furthermore,potentiallyfavorablegenecombinationsareoftendestroyedbyindiscriminateenvironmentalforcessuchasstorms,floods,earthquakes,orvolcaniceruptions,withoutnaturalselectionbeinggiventheopportunitytofavorthesegenotypes.Yetovertime,

inthesurvivalofthosefewindividualsthatbecome

11.Accordingtoparagraph6,environmentalforces

limitthepowerofnaturalselectioninwhichofthefollowingways?

A.Theychangethereproductiveprocessinsignificant

ways.

B.They

destroy

potentially

favorable

gene

combinationsbeforetheycanbeselected.

C.They

interfere

with

the

transmission

of

chromosomesfromparenttooffspring.

D.Theyweakentheabilityofindividualstomaintain

highfitnesslevels.

theancestorsofsubsequentgenerations,

fitnessalwaysplaysamajorrole.

relative

12.Theword”indiscriminate”inthepassageiscloset

inmeaningto

14

13.Lookatthefoursquares[■]thatindicatewherethefollowingsentencecouldbeaddedtothepassage.

Wherewouldthesentencebestfit?Clickonasquare[■]toaddthesentencetothepassage.

Newmodelsofthegenotypedepictamuchmorecomplicatedrelationshipamonggenes.

14.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.Completethe

summarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewText

Geneticsandenvironmentalfactorsoftenpreventorganismsfromachievingevolutionaryperfection.

Darwinfirstchallengedtheideaofevolutionaryprogressbyobservingthatmorethan99.9percentofallevolutionarylinesthatonceexistedonEarthhavebecomeextinct.

Asingleadaptationtoanorganism’senvironmentmaydeterminethewayinwhichtheorganism’ssubsequentancestorsareabletoevolve.

Thestructureofthegenotypeitselfrestrictsnaturalselection,sincegenesmustlineuplikepearlsonanecklaceandcannotbemovedoutoftheirproperorder.

Thedevelopmentofvertebrat