Môn Sinh học - Chapter 24: The origin of species

Ch. 23 Warm-UpUse the following information to help you answer the question below: Population = 1000 people AA = 160 Aa = 480 aa = 360What are the genotypic frequencies? Allele frequencies?Use directional, stabilizing or disruptive selection to answer the following:The mice in the Arizona desert have either dark or light fur.Birds produce 4-5 eggs per clutchAverage human baby weighs 7 lbs.Darwin's finches and beak size during droughtChapter 24The Origin of SpeciesWhat You Need to Know:The difference between microevolution and macroevolution.The biological concept of a species.Prezygotic and postzygotic barriers that maintain reproductive isolation in natural populaitons.How allopatric and sympatric speciation are similar and different.How autopolyploid or an allopolyploid chromosomal change can lead to sympatric speciation.How punctuated equilibrium and gradualism describe two different tempos of speciation.Speciation = origin of speciesMicroevolution: changes within a single gene poolMacroevolution: evolutionary change above the species levelcumulative effects of speciation over long periods of timeHHMI Video Clip: Reproductive Isolation and SpeciationRunning Time: 2:38 minBiological Species ConceptSpecies = population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspringReproductively compatibleReproductive isolation = barriers that prevent members of 2 species from producing viable, fertile hybridsTypes of Reproductive BarriersPrezygotic Barriers:Impede mating/fertilizationTypes:Habitat isolationTemporal isolationBehavioral isolationMechanical isolationGametic isolationPostzygotic Barriers:Prevent hybrid zygote from developing into viable adultTypes:Reduced hybrid viabilityReduced hybrid fertilityHybrid breakdownREDUCED HYBRIDVIABILITYREDUCED HYBRIDFERTILITYHYBRID BREAKDOWNTypes of Reproductive BarriersREDUCED HYBRIDVIABILITYREDUCED HYBRIDFERTILITYHYBRID BREAKDOWNTypes of Reproductive BarriersOther definitions of species:Morphological – by body shape, size, and other structural featuresEcological – niche/role in communityPhylogenetic – share common ancestry, branch on tree of lifeTwo main modes of speciationTwo main modes of speciation:Allopatric Speciation“other” “homeland”Geographically isolated populationsCaused by geologic events or processesEvolves by natural selection & genetic driftEg. Squirrels on N/S rims of Grand CanyonSympatric Speciation“together” “homeland”Overlapping populations within home rangeGene flow between subpopulations blocked by:polyploidysexual selectionhabitat differentiationEg. polyploidy in crops (oats, cotton, potatoes, wheat)Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon2n = 64n = 124n2nAutopolyploid SpeciationSympatric Speciation by PolyploidyAutopolyploid: extra sets of chromosomesFailure of cell division (2n  4n)Eg. Strawberries are 4n, 6n, 8n, 10n (decaploid)!Allopolyploid: 2 species produce a hybridSpecies A (2n=6) + Species B (2n=4)  Hybrid (2n=10)AllopolyploidyAdaptive RadiationMany new species arise from a single common ancestorOccurs when:A few organisms make way to new, distant areas (allopatric speciation) Environmental change  extinctions  new niches for survivorsEg. Hawaiian archepelagoFounding ParentsKAUAI5.1millionyearsOAHU3.7millionyearsHAWAII0.4millionyears1.3millionyearsMAUIMOLOKAILANAIArgyroxiphium sandwicenseDubautia linearisDubautia scabraDubautia waialealaeDubautia laxaNAdaptive Radiation: Hawaiian plants descended from ancestral tarweed from North America 5 million years agoHybrid ZonesIncomplete reproductive barriersPossible outcomes: reinforcement, fusion, stability“Grolar” or “Pizzly”GrizzlyPolarGradualismCommon ancestorSlow, constant changePunctuated EquilibiumEldridge & GouldLong period of stasis punctuated by short bursts of significant changeTempo of EvolutionHHMI Short Film:Lizards in an Evolutionary TreeTopic: Adaptive RadiationRunning Time: 17:50 min