Chapter 26Saturday, February 13, 20164:21 PM Chapter 26: Phylogeny and the Tree of Life Classification and Phylogeny-Taxonomy: grouping species togetheroGroups (taxa) based on their similarities and differences (subjective)oEx. Leopard, lion, tiger - similarities: legs, tail, fur; differences: patterns vs. no pattern-Linnaeus's hierarchical classification system is nestedoGroups of lower taxa from higher taxa-All species in any taxonomy-Phylogeny = the evolutionary history of a species and its relationship to other specieso[26.4] Shown as a "tree" o[26.5] each branch point…(rec)-Which of these is different from the other two?oBe able to recognize treesoC is different (C and D are sister taxas in A and B)oTrees may show time of divergence-Based on fossils, genetic evidenceoSystematics = (field of study) study of phylogenic relationshipsoTo create monophyletic taxa-Each taxon includes ancestor and all descendants-[26.10]oParaphyletic taxon = (off to the side) leaves out a common descendant-Leaving out "uncle joe" in group IIoPolyphyletic taxon = includes species with different ancestors-Adding new branch, additional branch without common ancestoroIdeally, taxonomic level relates to phylogeny-[26.4] oCladistics is a method of determining phylogenyoMust identify homologous (because of relationships, not recent adaptations) characters in a group as ancestral or derivedoCreate dichotomous trees-Based on shared derived characters (synapomorphies)oUse principle of "maximum parsimony" to choose best tree-Fewest evolutionary events (assume that that is the actual thing that happened)oInterpreting cladistic treesoClade = all the species on a branch-[] bass including all of its descendants-One clade including frog, turtle, leopard-Living in water: NOT A CLADE-Clip the branch, but turtle and leopard falls toooAll species in a clade share homologies-The more shared characters, the closer the relationshipoCan infer the sequence of evolutionary events from cladistic trees (but not absolute time)-Character shared by all = earliest-Unique character = most recentoHomologous DNA/genes also reveal relationships-Will be passed down in descendent species-Orthologous genes are inherited from common ancestor-Infer: more mutations = more time since divergence and less closely related-Won't be a lot of difference-Can go back after deletion and insertion, and infer "hypothetical sequence whenspecies diverged"-Molecular-based phylogenies can refine or change older trees-Can now say which branched off/separated first-Molecular clocks estimate divergence times-Assumes constant rate of "neutral" homologous DNA mutations over time-Calibrated with known fossil ages The Tree of Life-Older Five-Kingdom SystemoAll placed together in MoneraoCell walls and photosynthetic - PlantaeoCell walls and not photosynthetic - Fungi-Current 3-Domain System-The Tree of LifeoLast universal common ancestor-Common ancestor of eukaryotes and prokaryotesoThe "root" of the tree is complicated by horizontal gene transfer-[26.23] On the left, ancestor to all life-Cells intermingling, sharing genetic information-Taking DNA and transferring it to another species that it is not related to-Horizontal transfers of