Phylogeny Continued 1030.docx

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Craig Albertson

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Phylogeny Continued 10302013 90200 AM thReview session Monday the 4 8pm in here General features of animal diversification Changes in the number of repeated partsMeristic variationDiversificationindividualization of serially homologous partsSeries of reiterated partso whathow it happened Diversification of homologous partsEvolution of morphological noveltiesHox Genes increase in complexity in body plan from sponges to more complicated organismsthe what How did the complexity evolve Expanding genome sizeo Expanding theof hox genes hox genes build organisms the more hox genes the more complicated an organism you can buildo Sponges no hox genes no long axis of body Cnidarian two hox genes dont have a long axis of body but have topbottom o BlueposteriorRedanteriorIncreased number of Hoxincreased complexity in body planIncreasedof hox genes does NOTspecies diversity Increased number of Hoxspecies diversityBony fishes most diverse lots of hox genes but athropods have a fraction of those hox genes and there are 10s of millions of arthropods Metazoan PhylogenyEvolutionary diversification within phyla occurred within the context of shared genetic machineryHow Changes in when and where genes are turned on o ie variation in gene expressionNot differences inof genes but when and where the genes are turned on over development which hox genes are expressed in which segments segment identityincrease diversity Evolutionary diversification within phyla via variation in gene expression 1 Arthropod lineages are defined in part by their unique set of appendages 2 Appendage type depends on which Hox genes are expressed in the corresponding body segment during developmentSeries of head segments each segment has a particular set of hox genes and which ones are expressed determines what will grow from the segment 3 Variation in appendage type between species is due to shifts in Hox gene expression over developmentEg Variation in the expression of UbxAbdA is associated with the evolution of maxilliped number in crustaceans o instead of developing a leg they get a feeding maxillipedo variation inof maxilliped is determined byof UBxEg Variation in the expression of Ubx is associated with the evolution of wings in hexapods o Ubx inhibits wing formationwhyhow some have two or 4 wingsSuperphylum Deuterostomia
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