Bio Exam 2 notes

Bio Exam 2 notes - 2/28/2008 I. II. III. IV....

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Unformatted text preview: 2/28/2008 I. II. III. IV. Whatisevolution? Earlyideasonevolution Darwin Adaptation Whatisevolution? Accumulationofinheritedchangeswithpopulationsovertime Population o Groupofindividualsofonespeciesandlivein Samearea Atsametime Evolutiondoesnot o Refertochangeinoneindividualinitslifetime Evolutiondoes o Refertochangesincharacteristicsofpopulationsovermanygenerations Species o Groupoforganismswith: Similarstructure Function Behavior 2MainTypes: o Microevolution Minorevolutionarychangesofpopulationsoverafewgenerations o Macroevolution Majorevolutionaryeventsoveralongtimeperiod Formationofanewspeciesfromcommonancestors Evolution.. o Linksallfields o Commonthreadsbetweendifferentorganisms o Practicalapplications: Fluvaccinedevelopment Bioremediation Drugdesignanddevelopment PreDarwinianIdeas Aristotle(384322BC) o Sawnaturalaffinities o Arrangedorganismswin"scaleofnature" LeonardodaVinci(14521519) o Correctlyinterpretedfossilrocks CarolusLinnaeus(17071778) o Sweedishphysician/botanist o Founderoftaxonomy Naming/classifyingsystem Genusspeciesnamingsystem Hierarchyofsimilarity Didnotincludeevolutionarykinship Religionhadamajorinfluenceonevolutionarytheory JeanBaptistedeLamark(17441829) o Organismsundergochangeovertimeduetophenomena o Changingenvironmentscausedanorganismtoalteritsbehaviorchangingitsshape o DiscreditedwhenMendel'stheoriesrediscovered~1900 o Lamark'sTheory Giraffestretchesit'sneckwhileeating Neckbecomeslonger Giraffepassesdownthislongernecktoitsoffspring Darwin CharlesDarwin(18091882) o Careerpath:medicinetheologybotanynaturalworld o EmbarkedonHMSBeaglein1831 5yearcruisearoundworldtomakenavigationchartsforGreatBritain Didnotpublishhisfindingsuntil1859 SpentalotoftimeinGalapagosIslands HMSBeagletrip o BasisforDarwin'sTheoryoEvolution o Similaritiesbetweenanimals,plantson: AridGalapagosIslands(volcanic) Andbetweenislands HumidSouthAmericanmainland o Collected,categorizedthousandsofplant,animalspecimens Darwinnoticed o MostanimalsonGalapagoslivednowhereelseonearth o ResembledSouthAmericanspecies o Galapagosrelativelyyoung o Wasitcolonized? InfluencesonDarwin o PrinciplesofGeologybyLyell Geologicalprocessesdevelopedslowly Earthisold o Artificialselection Breedersdevelopingmanyvarietiesofdomesticatedanimalsinfewgenerations Chicken,dogs Plantvarieties 7foodplants,samespecies o ThomasMathus(17661834) Britisheconomist Populationgrowthnotalwaysdesirable Populationgrowthincreasesgeometrically:124816 Foodsupplyincreasesarithmetically:12345 Consistentcheckonpopulationgrowth(disease,war,faminenecessary) Adaptations Individualsinstruggletosurvive Inheritedvariationsfavorabletosurvivalpersevere Unfavorablevariationseliminated Eventuallyenoughchangestoformnewspecies Timeneeded AlfredRussellWallace o LivedatsametimeasDarwin o Englandnative o Naturalhistorycollector ButterfliesinMalaysia o Observedsameprocessesofadaptation WallaceandDarwin o Formulatedthesameideasaboutnaturalselectionatthesametime 2/27/08 NaturalSelection 1. Adaptation/TheoriesofEvolution 2. Modernsynthesis 3. Evidenceofevolution Adaptation Variationsfavorabletosurvivalarepassedon Unfavorablevariationsareeliminated Enoughchangesnewspecies Anotherscientist... o AlfredRussellWallace LivedatthesametimeasDarwin England Naturalhistorycollector Butterflies,etc Alsoobservedadaptations WallaceandDarwin o Formulatedthesameideasofnaturalselectionatthesametime Darwin o PublishedTheOriginofSpeciesin1859 TheoryofEvolutionbyNaturalSelection o Variationofspecies Individualsinpopulationsexhibitvariation Sometraitsincreasesurvivalandreproduction Somedon't Traitsheritablefornaturalselection o Overproduction Reproductiveabilityofaspeciescanmakeapopulationincreasegeometrically 2frogs4816 2frogs61854 o Limitsonpopulationgrowth Resourcesarelimited Water,food,light,space,etc Organismsinstruggletosurvive o Differentialreproductivesuccess Individualswithmostfavorablecharacteristicsmostlikelyto Survive Reproduce Successfultraitsareinherited Overenoughtime.. o Naturalselection,geographicseparationmayproducenewspecies o RecallDarwin'sfinches 1speciesonSouthAmericanmainland 13speciesonGalapagosislands GiraffesbyDarwin o Thosewithlongernecks: Getbetterfood Havemorebabies Thushaveadvantages o Longernecksbegetlongernecks(variationisheritable) o Results Overtime,averagenecklengthincreases Darwindidn'tknowaboutDNA;couldnotexplain o Howevolutionbynaturalselectionoccurs o Whyindividualsinpopulationvary RecallGregorMendel o Botanicalexperiments Peaplants o Variationsheritable Modernsynthesisofevolution o Beganin1930s/1940s o Manyscientists o Combinesprinciplesof: Naturalselection Mendellianinheritance Modernsynthesis o Mutationprovidesgeneticvariabilityonwhichnaturalselectionacts DNA o Includesknowledgein: Genetics Systematics Ecology,etc Whataboutchance?(Naturevs.Nurture) o Evolutionoffruitflies(differenceinwingsize) o NorthernEuropeanflieshavelargerwingsthansouthern o In1970saccidentalintroductionsto: NorthAmericaandSouthAmerica Results: 10yearsafterward: Nosignificantdifferenceinwingsize 20yearsafterward: SamepatternasinEurope Unknownwhywingsizevariesbyclimate Evidenceofevolutionin: o Fossilrecords o Molecularbiology o Developmentalbiology o Andotherfields Typesoffossils: o Dinosaurs o Petrifiedwood o Footprints o Amber o Imprints Fossilinformation o Organismburiedinconditionsthatslow/preventdecay Trappedinfinesoil(likeamudflat) Morefossilsfoundthatare: Aquaticvs.terrestrial Polar/temperatevs.tropical Hardbodyparts Fossils o Directevidenceofevolution o Progressionfromearliestunicellularorganismtoday o Showslifehasevolvedthroughtime o Earthis4.5billionyearsold Eachfossilisaseparatetestofevolution o Sedimentarylayers Youngerolder Butsedimentarylayersshift o Insteaduseradioactiveisotopes(Carbon14dating) o 2/29/08Evidenceofevolution Fossils o Progressionfromearliestunicellularorganismstotoday o Earthis4.5billionyearsold o Eachisaseparate`test'ofevolution Sedimentarylayers o Youngerolder o Sedimentarylayerscanshift o Insteaduseradioactiveisotopes(C14) Infossils/volcanicrock Datesfossilandrock Emitradiationasnucleuschangesthroughradioactivedecay Eachhasownrateofdecay/characteristicnumber Halflifetimeforoftheatomstochangeintodifferentatoms Carbon14 o Continuouslyproducedintheatmospherefromnitrogen14 o RatioofC14andC12isstableinatmosphere o Livingorganismsabsorbbothcarbons o Whentheydie,C14N14 o Halflife=5736years Comparativeanatomy o Examinestructuraldetailsofspecies o Homologousfeatures: Derivefromsamestructureincommonancestor Homologyinanimals Homologyinplants:modifiedleaves Homoplasticfeatures o Similarfunctionsindistantlyrelatedspecies o Homoplasy(thornandspinesamefunction)dealwiththesameproblemandsolution,done in2differentways o Homoplasyshows... Convergentevolutionindependentevolutionofsimilarstructures Indistantlyrelatedspecies Example:mammalswhoeatantsandtermites o Anteater o Aardvark o Pangilion Vestigialstructures(noevolutionaryadvantage,noreasontohavethem/getridofthem) o Africanrockpython o Inhumans: Thirdmolars(wisdomteeth) Coccyx(fusedtailbone) Nipples(inmales) Earth o Evolutiononearth Continentaldriftveryimportant AlfredWagener(1915) Similarityincontentshapes 1960sevidencebecameclear(onemassivesupercontinentexistedatonepointin time) PlateTectonics(finishandfix) Pangea Continentaldrift o Separatespopulationsoforganisms o Changesclimatepatternsandoceancurrents Molecularevidence o ProteinsandDNAcontainrecordofevolutionarychange o Closelyrelatedtospecieshavecloselyrelatednucleotidesequence Molecularclock o Mutationsoccuroverfairlysteadyrate o Overmillionsofyears o LookatalterationsinhomologousDNAsequencestoestimatetimeofdivergence 3/3/2008HardyWeinberg Apopulation'sgenepool o Includesallallelesforalllocipresentinthepopulation o Diploidorganisms: Max.of2differentallelesofeachgeneticlocus o Usually,1individualhassmallfractionofallelespresent EvolutionofPopulations o Genotype o Phenotype o Allele Genotypefrequencies(forall1000individualsofapopulation) Genotypes Number AA 490 Aa 420 Aa 90 Total 1000 CalculatingPhenotypes o Dominant:AA+Aa o Recessive:aa Phenotypefrequencies Phenotype number Dominant 910 Recessive 90 Total 1000 Calculatingallelefrequencies Genotypefrequency 0.49 0.42 0.09 1.00 Phenotypefrequency 0.91 0.09 1.00 If1000individuals,thereare2000alleles AlleleA 490AAx2+420Aa=1400 o Allelea 420Aa+90aax2=600 Allelefrequencies o o Number 1400 600 2000 Allelefrequency 0.7 0.3 1.0 Allele A A Total Geneticequilibrium o Populationwhosegenotype,phenotypeandallelefrequenciesdonotchange o HardyWeinberg(1908) Mathematicaldescriptionofthis HardyWeinbergEquilibrium: o Stabilityofsuccessivegenerationsinpopulationaequilibrium o Essentialtounderstandingevolutionarychange o HardyWeinbergequation p=frequencyofdominantallele q=frequencyofrecessiveallele p+q=1 (p+q)2=1 Genotypefrequencies o P2+2pq+q2=1 p2=frequencyofhomozygousdominantgenotype 2pq=frequencyofheterozygousgenotype q2=frequencyofhomozygousrecessivegenotype Aa Aa 0.42 0.09 /\ 0.210.21 Frequencyingametes \/\/ 0.700.30 o ifexpectedF1genotypesmatchedtheobservedF1genotypes,populationisingenetic equilibrium o ifnot..naturalselectionisoccurring HardyWeinberg o Dominantallelesnotnecessarilymorecommonthanrecessivealleles o Ifpopulationislarge,inheritancedoesnotchangeallelefrequencies Geneticequilibriumrequires... o Randommatings o Nonetmutations o Largepopulationsize o Nomigration Genotype Frequencyin population AA 0.49 o o 3/5/08GeneticVariations Microevolution Geneticvariation Microevolution o Intergenerationalchangesinallele/genotypefrequencies Withinapopulation o Involvessmallandminorchanges o Occursinfewgenerations o Changescausedby... Nonrandommating Interbreeding o Interbreedingdepression(fitnessofapopulationdrops) Assertivemating(similarphenotypes;generallypositivebetterabletosurvive, moredesirablemate) Increasefrequencyofhomozygotes o Increasesvariationinpopulation Mutation: Unpredictable Spontaneous OnlythoseinDNAofreproductivecells o Changescausedby... Geneticdrift=productionofrandomeventschangesinsmallpopulations Changesinallelefrequenciesovertime Randomevens Decreasesvariationwithinpopulation Increasesvariationamongpopulations Bottleneck(severedeclineingeneticfrequencies/variationsaren'ttolerated) Nonaturalselection Example:HumanMNbloodgroups Antigensonsurfaceofbloodcells 1groupsisMN M,Ncodominant MMproducesMantibodies MNproducesM,Nantibodies NNproducesNantibodies MN Allgenotypesarevisible o MM320 o MN480 o NN200 o Total1000 Determine: o FrequencyofM,Nalleles o ExpectedMM,MN,NN o Doesthismatchobserveddata? o Howdothefivefactorsplayarole? o Seetextp.415 Geneflow Migrationofindividualsbetweenpopulations Movementofallelesbetweenpopulations Increasevariabilitywithinrecipientpopulation Reducesthevariationbetweenpopulations o Naturalselection Leadstoadaptiveevolutionarychange Explainsdiversityoflife,adaptation Operatesonphenotype Noselection Stabilizingselection Directionalselection(segregation) Disruptiveselection(selectedagainstpopulations) Geneticvariationcausedby... o Mutations o Sexualreproduction Allowsnewphenotypes o Geneticpolymorphisms 2ormorealleles/locus Howisthismaintained? Decreasesovertime Heterozygousadvantage o Heterozygousadvantage Heterozygotehashighestfitness Sicklecellalleleexample NormalhemoglobinHbA SicklecellalleleHbS HbSHbSusuallydieatyoungage HbAHbA,HbAHbSlivelonger Malaria HbSismoreresistanttomalariaparasite Heterozygoteadvantagewheremalariaispresent o Frequencydependentselection Fitnessofphenotypedependsuponitsfrequencyinthepopulation Greaterselectivevaluewhenrare Ofteninpreyspeciesorinplants Examplecichlids o o examplecheetahs Foundereffect(reducedvariationingenesisolation) Notusuallyadaptive 3/7/08ReproductiveIsolation Whatisaspecies? o Notonmorphologyalone Polymorphisms Siblingspecies(morphologicsimilaritybutnoninterbreeding) Examplethetwotypesoffruitflies Biologicalspeciesconcept o ErnstMayr1942 o 1ormorepopulationswhose: Membersdo/mayinterbreedinnature Producefertileoffspring Donotinterbreedwithotherspecies Reproductivebarriers Genepool o Problem#1 Whataboutasexualreproducers? Bacteria Nointerbreeding Classifiedbasedon: Structure Biochemistry o Problem#2 Individualindifferentspeciessometimecaninterbreed Examplezebras EvolutionarySpeciesConcept o Orphylogeneticspeciesconcept o Tobeaspecies: Apopulationmusthaveundergoneevolutionlongenoughtohavesignificant differencesinsometraits Istestable o Problems Evolutionaryhistoryofmostgroupspoorlyunderstood Woulddoublethenumberofspecies Sowhatisaspecies? o Willgenerallyusebiologicalspeciesconcept Prezygoticbarriers(preventsfertilizationfrombeingpossible) o Reproductiveisolation Preventsgeneflowbetweenspecies Prezygoticbarriers Preventmating/fertilization Postzygoticbarriers Reproductivefailureafterfertilization Prezygoticbarriers o Reproductiveindividualsdonotmeet(seasonal/habitatisolation) o Matesmeetbutdonotmate(ethologicalisolation) o Copulationattemptedbutnospermtransfer(mechanicalisolation) o Fertilizationisunsuccessful(gameticisolation) o Examples: Temporalisolation Woodfrog/leopardfrog o OverlappingregionsinUSandCanada o Differinreproducingtimes(temperaturedifferences) Mateatdifferenttimesofday o 2speciesofDrosphila o 1activeinthemorning/1activeintheafternoon Habitatisolation Differenthabitatsinthesamearea 5flycatchersrangeissame Behavioralisolation Malebowerbirdbuildsabowertoattractfemales Requirescourtshipbehaviors Courtshipdancesspeciesspecific Vocalizations Mechanicalisolation Commoninfloweringplants Flowerpartsadaptedforspecificpollinators(insects) o Geneticorgansincompatible o Example2sagespeciesinCA Gameticisolation Matingoccurs Eggandspermareincompatible Duetoproteindifferences Releaseofgametesatsametime Postzygoticbarriers o Zygotedies(zygotemorality) o ZygoteproducesF1ofreducedviability(hybridinviability) o F1hybridisviablebutsterile(hybridsterility) o F2hybridisproducedbutaresterile(hybridbreakdown) Hybridinviability Embryospontaneousaborts Genesdonoregulatenormaldevelopment Exampleirishybridembryosdie Hybridsterility Problemsduringmeiosiscauseabnormalgametes o Examplemule(horse+donkey) 3/10/08Speciation Howdoesanewspeciesarisefromexistingones? o Speciation Evolutionofanewspecies o Populationbecomesreproductivelyisolatedfromotherpopulations o Genepoolsdiverge o Nogeneexchange Speciation o Mostlikelytooccuriforiginallyisolatedpopulationissmall Thinkofgeneticdrift Foundereffect Allopatricspeciation o 1populationbecomesgeographicallyseparated o Evolvesby: Naturalselection o o o o Geneticdrift Intoanewspecies Changesinalleles,allelefrequencies Mostcommonmethodofspeciation Responsibleformostanimalspecies: 2differenttypes: Dispersal(onecontinuouspopulationsmallgrouptoanew islandislandpopulationbeginstodivergeduetodriftand selection2populationsisolatedfromoneanother) o Example:HawaiiangeeseNene Feetnotcompletelywebbed Footpadsthicker Toenailsstronger Allowsforwalkinginlavaflows OriginatedfromNorthAmericangeese o Example:PortoSantoRabbits Early1400s,rabbitswerereleasedonanislandnear Portugal Nocompetitors/predators 1800s,rabbitsdiffered Halfaslarge Differentcolorpatterns Can'tmatewithmainlandrabbits Aretheyanewspecies? Orisspeciationinprogress? Vicariance(continuouspopulationchanceeventthatchangesthe landscapeisolatedpopulationbeginstodivergeduetodriftand selection2populationsisolatedfromoneanother) Usuallyoccursamongaquaticanimals Continentaldrift Evolutionofmanyspecies Example:Ratiteslargeflightlessbirds Example:desertpupfish o LastIceAge(until~12,000years ago) Largeinterconnectedlakes inCAandNV Populatedbypupfish o Climatebecamedrierlakesdried up o Isolatedpoolsremain o Smallnumberofpupfishineach pool o Divergingfromcommonancestor via Naturalselection Geneticdrift o o Sympatricspeciation o Newspeciesevolveswithinthesamegeographicareaasparent o Reproductiveisolatingmechanismevolvesatstartofspeciationprocess o Morecommoninplants ChangeinPloidy: Chromosomenumberdoublesbeforemeiosis Polyploidy o 2setsofchromosomes o Arisesin1generationresultsinanewspecies 2typesofPolyploidy: o Autopolyploid Multiplesetsofchromosomesfromasinglespecies Rare o Allopolyploid Multiplesetsofchromosomesfrom2ormore species Muchmorecommon Hybridization80%offloweringplantsare polyploidy ChangeinEcology: Frequencyisdebated Parasiticinsectsandhosts Example:Maggotfly o Populationoffruitmaggotfliesswitchedhosts o Fromnativehawthorn o Tonewdomesticapple o Nogeneflow o Why?Mutationleadstodisruptiveselection Hightemperature,salt concentration,lowoxygen Today:20speciesofpupfish 3/12/08Macroevolution Evolutionarychange Macroevolution Rateofevolutionarychange: o Problems: Fossilrecordisnotcomplete(yet?) Intermediateformslacking o 2differingviews/models: Punctuatedequilibrium Paleontologists1970s Fossilrecorddoesaccuratelyreflectevolution Longperiodsofstasis(nochange) Shortperiodsofrapidspeciation(muchchange) o Triggeredbychanges? o Spurts 100,00years Vs.millionsofyearsofstability Promptedbyenvironmentalchange(quickanddramatic) Thus,fewtransitionalformsinfossilrecordsincefew occurred Gradualism Traditionalview Evolutioncontinuous,overlongperiods Rarelyseeninfossilrecordduetoincompletestatus Whichisright? Probablysomeofboth Somemutationsmaynotbevisibleinfossils Mostmutationsdon'tcausespeciation Macroevolution o Largescalephenotypicchangesinpopulations o Placementinnewtaxonomicgroups o Appearanceofevolutionary"novelties"--somethingadvantageous o Preadaptations Featuresthatoriginallyfulfilledonerole Butbecomeadaptiveindifferentrole feathersoriginallyprovidedthermalinsulation aftergradualchange,servednewfunctioninflight arisesduetochangesindevelopment regulatorygenescontroldevelopment changesingenesmajorstructuralchangesinorganism o Allometricgrowth Inhumans,headlargeatbirth Duringgrowth,torso,etc.growfaster o Development Changesintiming Ex.Juvenilecharacteristicsretainedintoadulthood Salamanderpaodomorphosis o Adultwithexternalgills o Abletoincreaseenvironmentalrange o Adaptiveradiation One/fewancestralspecies Manyrelatedspeciesinshortperiodoftime Adaptivezones: Mayappearwhenenvironmentchanges Ecologicalniche o Vacantadaptivezones Morecommononislands Islandshavefewerspeciesthanmainlandareasofsimilarsize,etc Onespeciesmaycolonizeislandanddiversifyintoseveral Ex.BirdsofHawaii--differentbillsadaptedtocoordinatewiththe environmenttheylivein,sotheycaneffectivelygettheirfood o Extinction o Occurswhenthelastindividualofaspeciesdies Ispermanent ~1speciesaliveforevery2000extincttoday Makesanadaptivezonevacant Providesanewopportunityforotherspecies Extinctionrates Backgroundextinction Continuouslowlevelrate Massextinction 56timesinEarth'shistory Manyspeciesdieinshorttimeperiod o 9095%oforganismsdies o Short=fewmillionyears Adaptiveradiationfollows(canexploitresources) Climatechange Particularlyforspecieswith o Narrowtemperaturerange,especiallymarine Catastrophes Comet/asteroidcollision Dustejectedintoatmosphere Blocksunlight Reducephotosynthesis Disruptfoodchain Loweredtemperatures ...
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This note was uploaded on 07/24/2008 for the course BIO 102 taught by Professor Thornber during the Spring '06 term at Rhode Island.

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