Download CH. 16.1 – Genes and Variation How Common Is Genetic Variation

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Transcript
CH.16.1–GenesandVariation
HowCommonIsGeneticVariation?
VariationandGenePools
Geneticvariationisstudiedin_______________________orgroupof
individualsofthesamespeciesthatinterbreed.
A___________________________consistsofallgenes,includingallthedifferent
alleles,thatarepresentinapopulation.
Therelativefrequencyofanalleleisthe___________________________________
______________________inagenepool,comparedwiththe_____________
______________________________(usuallyexpressedasapercent).
Howisevolutiondefinedingeneticterms?
Ingeneticterms,evolutionis___________________________intherelative
frequencyofallelesinapopulation.
Whatarethemainsourcesofheritablevariationinapopulation?
SourcesofGeneticVariation
Thetwomainsourcesofgeneticvariationare________________________
andthe_________________________thatresultsfromsexualreproduction.
Mutations
Amutationis___________________________inasequenceofDNA.
Mutationsoccurbecauseof_____________________inDNA____________________
orasaresultofradiationorchemicalsintheenvironment.
Mutations___________________alwaysaffectthewayanorganismlooks,or
itsphenotype.
GeneShuffling
Mostheritabledifferencesaredueto___________________________.
Crossing-over,whichoccursduringmeiosis,_____________________the
numberofgenotypesthatcanappearinoffspring.
Sexualreproductionproduces______________________phenotypes,butit
doesnotchangetheamountofallelesinapopulation.
16-2EvolutionasGeneticChange
Naturalselectionaffectswhichindividuals________________________and
______________________and___________________________.
Ifanindividualdieswithoutreproducing,it_______________________
contributeits_______________________tothepopulation’s____________________.
Ifanindividualproduces_____________________________,its____________________
___________________________andmayincreasein_________________________.
Evolutionisanychangeovertimeintherelativefrequenciesofallelesin
apopulation.
_______________________,notindividualorganisms,can________________________
__________________.
NaturalSelectiononSingle-GeneTraits
Howdoesnaturalselectionaffectsingle-genetraits?
Naturalselectiononsingle-genetraitscanleadto_____________________
________________________andthusto____________________.
Organismsofonecolormayproducefeweroffspringthanorganismsof
othercolors.
Forexample,alizardpopulationisnormally__________________,buthas
________________________thatproduce____________and_______________forms.
Redlizardsaremorevisibletopredators,sotheywill____________________
____________________________________.Therefore,thealleleforredcolorwill
become________________.
Blacklizardsmaywarmupfasteroncolddays.Thismaygivethem
energyto_______________________________________.Inturn,theymayproduce
_________________________________.
Thealleleforblackcolorwill________________________________________________.
NaturalSelectiononPolygenicTraits
Howdoesnaturalselectionaffectpolygenictraits?
Naturalselectioncanaffectthedistributionsofphenotypesinany
ofthreeways:
•___________________________selection
•___________________________selection
•disruptiveselection
DirectionalSelection
Whenindividualsatoneendofthepopulationcurvehave________________
_______________________thanindividualsinthemiddleorattheotherend,
directionalselectiontakesplace.
Therangeofphysicalcharacteristics,________________________,shiftsas
someindividualssurviveandreproducewhileothersdonot.
Inthiscase,birdswithlargerbeakshave__________________________.
Therefore,theaveragebeaksize______________________.
Drawgraphbelow…
StabilizingSelection
Whenindividualsnearthe_________________________________havehigher
fitnessthanindividualsateitherendofthecurve,stabilizingselection
takesplace.
Thiskeepsthecenterofthecurveatits________________________________,but
itnarrowstheoverallgraph.
Humanbabiesbornatanaveragemassaremorelikelytosurvivethan
babiesborneithermuchsmallerormuchlargerthanaverage.
Drawgraphbelow…
DisruptiveSelection
Whenindividualsatthe____________________and_____________________ends
ofthecurvehavehigherfitnessthanindividualsnearthemiddle,
disruptiveselectiontakesplace.
Ifthepressureofnaturalselectionis__________________enoughand
____________________enough,thecurvewill______________,creatingtwo
distinctphenotypes.
Ifaverage-sizedseedsbecomescarce,abirdpopulationwillsplitinto
twogroups:onethateatssmallseedsandonethateatslargeseeds.
Drawgraphbelow…
16.2cont…
GeneticDrift
Whatisgeneticdrift?
A__________________________________in_______________________________________is
calledgeneticdrift.
In_________________populations,individualsthatcarryaparticular
allele,orcharacteristic,mayleavemoredescendantsthanother
individualsdo,just_____________________________.
_______________________,aseriesofchanceoccurrencesofthistypecan
causean_____________________tobecome_________________inapopulation.
Geneticdriftmayoccurwhena________________________ofindividuals
colonizesa_______________habitat.
Thoseindividualsmaycarry_________________ofa___________________________
thanthelargerpopulationhad.
Thenewpopulationwillbe________________________________________________
fromthe________________________population.
Whenallelefrequencieschange________________________________ofasmall
subgroupofapopulationitisknownasthe_______________________________.
EX.Largerpopulationismadeupof…
FoundingpopulationAismadeupof…
FoundingpopulationBismadeupof…
DescendantsofpopulationAaremadeupof…
DescendantsofpopulationBaremadeupof…
EvolutionVersusGeneticEquilibrium
TheHardy-Weinbergprinciplestatesthat_________________frequencies
inapopulationwillremain_________________unlessoneormorefactors
causethosefrequenciesto_______________.
Whenallelefrequenciesremainconstantitiscalledgenetic
equilibrium.
Whatfiveconditionsareneededtomaintaingeneticequilibrium?
_______________conditionsarerequiredtomaintaingenetic
_____________________________fromgenerationtogeneration:
•theremustbe_____________________mating,
•thepopulationmustbevery__________________,
•therecanbe______________________________intooroutofthepopulation,
•therecanbe______________________________,and
•therecanbe________________________________________.
RandomMating
Randommatingensuresthat____________________________hasan____________
________________________ofpassingonitsallelestooffspring.
Doesthishappeninnature?
Arematesselectedduetosomedesirablecharacteristic?
LargePopulation
Smallpopulations_____________________reachgeneticequilibriumeasily
duetogeneticdrifthavinga________________________onasmallpopulation.
Allelefrequenciesoflargepopulationsare_______________________tobe
changedthroughtheprocessofgeneticdrift.
NoMovementIntoorOutofthePopulation
Becauseindividualsmaybring_____________________intoapopulation,
theremustbe___________________________________intooroutofapopulation.
Thepopulation'sgenepoolmustbekept_______________________andkept
______________________fromthegenepoolsofotherpopulations.
NoMutations
Ifgenesmutate,________________________maybeintroducedintothe
population,andallelefrequencies____________________________.
NoNaturalSelection
_______________________inthepopulationmusthave_______________
probabilitiesof______________________and________________________.
_______________________________canhaveaselectiveadvantageoveranother.
Therecanbe__________________________________operatingonthepopulation.
16-3TheProcessofSpeciation
Naturalselectionandchanceeventscan____________________________________
_____________________________________inapopulationandleadtospeciation.
Speciationistheformationof_______________________.
Aspeciesisagroupoforganismsthat__________________withoneanother
andproduce__________________________________________.
Thegenepoolsoftwopopulationsmustbecome__________________________
forthemtobecomenewspecies.
IsolatingMechanisms
Asnewspeciesevolve,populationsbecomereproductivelyisolated
fromeachother.
Whenthemembersoftwopopulations_____________________________________
andproducefertileoffspring,reproductiveisolationhasoccurred.
Reproductiveisolationcandevelopinavarietyofways,including:
•___________________________isolation
•___________________________isolation
•___________________________isolation
BehavioralIsolation
Behavioralisolationoccurswhentwopopulationsarecapableof
breedingwithoneanotherbuthave_________________________________________
orotherreproductivestrategiesthatinvolvebehavior.
GeographicIsolation
Geographicisolationoccurswhentwopopulationsareseparatedby
geographicbarrierssuchas___________________or___________________________.
Geographicbarriers_____________guaranteethecreationofanewspecies.
TemporalIsolation
Temporalisolationoccurswhentwoormorespecies___________________
_________________________________.
SpeciationinDarwin'sFinches
SpeciationintheGalápagosfinchesoccurredby:
•_________________________ofanewpopulation
•geographic__________________________
•changesinnewpopulation's________________________
•___________________________isolation
•ecological_________________________
FoundersArrive
SpeciesAcomesfrom____________________________totheGalapagos,
_______________________and_________________________
GeographicIsolation
SpeciesAtravelsto_________________________andcreatesanew
___________________________.
ChangesintheGenePool
________________________onthesecondislandfavorbirdswith
_________________beaks.
Pop.Bappearson_______________________with____________________________.
ReproductiveIsolation
IfpopulationBbirdscrossbacktothefirstisland,they__________________
___________________withbirdsfrompopulationA.
PopulationsAandBare____________________________.
EcologicalCompetition
AsspeciesAandBcompeteforavailableseedsonthefirstisland,they
continueto______________________inawaythatincreasesthedifferences
betweenthem.
A______________________________—C—___________________________.
ContinuedEvolution
Thisprocessofisolation,geneticchange,andreproductiveisolation
probablyrepeateditselfoftenacrosstheentireGalápagosislandchain.
Chapter17Notes
Section17.4PatternsofEvolution
Whatisadaptiveradiation?
Drawadiagramofadaptiveradiation.
Whatisconvergentevolution?
Giveanexampleofconvergentevolution.
Whatiscoevolution?
Giveanexampleofcoevolution.