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Final Review (Units 6, 7, & 8).docx

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University of Guelph
BIOL 2400
Cortland Griswold

Unit 6Species Concepts1Darwins Morphological ConceptoSpecies Varieties between which there are few or no morphological intermediates Groups of organisms that are morphologically distinct from other groups of organisms2Phylogenetic Species Concepts by HenningoA species is the smallest monophyletic group within which theres a contemporary pattern of parental ancestry and descent3Mayrs Biological Species ConceptoSpecies are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups Key reproductive isolation4Dobhanskys Biological Species ConceptoSpecies are systems of populationsthe gene exchange between these systems is limited or prevented by a reproductive isolating mechanism or perhaps by a combination of several mechanisms Key More open to interbreeding and reproductive isolation mechanismsprevent mating between speciesSummaryoNo definition of species works universallyoUsefulnesshighlights properties that we think are important for speciesShared Properties Between Species ConceptsInterbreeding individualsReproductive isolationSpecies Concepts in Bacteria and ArchaeaFocus on reproductive isolation does not make sense due to clonal reproductionTypically use a phylogenetic approach based on gene sequence similarityo97 Ruleif a specimens 16s RNA gene sequence is 97 similar to a known species then specimen is assigned to that species If not indication that its a new speciesIssues With this Approach as we probe deeper into genetic composition of species that theyre more complicated then they appear to beOccurrence of horizontal gene transfer and degree of gene sharing is changing our understanding of microbial speciesCauses of Reproductive Isolation Figure on next PagePrezygoticprocesses that occur before a zygote forms eg green lacewings hummingbirds Mimulus lewisii and M cardinalisoPremating Behavioural IsolationEcological IsolationMechanical isolationoPostmatingCopulatory Behavioural IsolationGametic IsolationPostzygoticprocesses that occur after a zygote forms eg Adenostoma and CeanothusoIntrinsicoExtrinsicThe Speciation processModes of Speciation1Allopatriceg lobsters when gulf of mexico was cut off from the pacific
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