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Ch 14 Objectives

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Biological Sciences
BIOL 3040
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Chapter Learning ObjectivesChapter 14 Species and Speciation141 The Species ProblemDefine and evaluate the pros and cons of the following species conceptsoEvolutionary species conceptSpecies is a lineage of populations which maintains its identity form other such lineages and which has its own evolutionary tendencies and historical fatePros defines what a species is and what role species play in evolutionary historyCons does not offer a way of how we should identify a species and draw species boundariesoPhenetic species conceptDraws species boundaries around clusters of phenotypically similar individuals or populationsPros helps to delineate species boundariesCons no way of weighing the relative importance of characters or traits used to delineate species boundariesoBiological species conceptA species is composed of groups of actually or potentially interbreeding populations which are reproductively isolated from other such groupsPros uses the pattern of gene flow to determine species boundaries Delineates species by properties possessed by populationsCons hard to apply this concept to extinct species And the occasional hybridization events between individuals in populations that are reproductively isolated Finally it is restricted to sexual speciesoPhylogenetic species conceptSpecies is the smallest monophyletic group distinguished by a shared derived characterPros determines an appropriate taxonomic level at which to draw species boundaries Does not require information about gene flowCons divides up organisms into more finegrained species categories than may seem appropriate Does little to ensure that species will have separate evolutionary fates in the future142 Modes of SpeciationDescribe and give an example of allopatric speciationoAllopatric speciation speciation takes place in populations that are geographically isolated from one another oEx Isthmus of Panama they found that tolerance decreased and aggression increased in transisthmus sister pairs as a function of how long they had been geographically isolated from one another by the isthmus of panama oDistinguish between the dumbbell and peripheral isolate models of allopatric speciation
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