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Lecture 20

Lecture 20 Speciation.docx

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Maria Arts

Lecture 20 Speciation CH 26 261264 Can Research 261 Can Issues 261 How Species Form defining a speciesspecies conceptssubspeciesecological and gnetic conditions required for speciation to occurreproductive isolating mechanismsspeciation modes allopatricsympatricpolyploidyhybridizationadaptive radiation Speciationpopulations of the same species become genetically isolated by lack of gene flow and diverge from each other due to selectiongenetic drift mutation and evolve independently Splitting event in which 2 species created from single ancestral groupSpeciesevolutionary independent populationgroup of pops How are Species Defined and Identifiedbiologists commonly define species by all 3 1 biological species concept 2 morphospecies concept 3 phylogenetic species concept Biological Species Concept groups of actuallypotentially interbreeding pops which are reproductively isolated from other such groupsErnst Mayt Biological Speciespopulations that can interbreed with one anotherve potential 2 pops put together can interbreed but dont because geographically isolated no gene flowreproductive isolation between population1 pre zygotic isolation different individuals cant mate temporal habitat behavioural genetic barrier eggssperm mechanical 2 postzygotic isolationoffspring do not survive or reproduce low fitness hybrid viability die as embroyssterlity mature but are steriledisadvantage cannot be evaluated in asexual reproductive organism bc its cell fertilizationthis concept does not apply to themor in fossils also when closely related populations do not overlap ex grizzly bears in europe north americato know if they are same species must bring them together Morphospecies Concept observed by looking at population morphology
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