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TAMU BIOL 112 - CH26

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Chapter 26 Phylogeny and the Tree of LifeClassification and PhylogenyLinnaean classification- Binomial nomenclature for species (scientific name)o Genus (family group) + “specific epithet” (species name)o Felis catus (genus is always capitalized and always written in italics)- Taxonomyo Groups (taxa) are based on similarities and differences But it is very subjective- Linnaeus’s hierarchical classification system is nestedo Groups of lower taxa (species, genus) form higher taxa All species in any taxon share certain featuresPhylogenetic Trees- Phylogeny is the evolutionary history of a species and its relationship to other specieso Shown as a tree (fig 26.4 and 26.5)- Branch point is where lineages diverge- Polytomy is an unresolved pattern of divergence- Sister taxa are the par that shares the most recent common ancestor- Basal taxon is a n old/remnant species that hasn’t changed for a long timeSystematics- Systematics is the overall study of phylogenetic relationships- Based on homologieso Of morphology (26.11)o Of DNA sequences (26.8)- But morphological differences can be much greater than DNA differenceso Adaptive radiation of Hawaiian plants- Taxa and trees should correspond- The goal is a monophyletic taxa (26.10)o Each taxon includes an ancestor and all of its descendants- Paraphyletic is a taxon that leaves out a common descendant- Polyphyletic is a taxon that includes species with different ancestorsSystematicsCladistics- Purpose: Hypothesize phylogeny in the form of a dichotomous tree (2 branches)- Method: Identify characteristics as ancestral or derivedo Create the most “parsimonious” tree based on shared derived characteristics (synapomorphies)- Interpreting cladistic tree (clado=branch)o Clade= all the species on a brancho All species in a clade share homologies The more shared derived characteristics, the closer the relationshipo Infer the sequence of evolutionary events Characteristics shared by all are the earliest in history Unique characteristics are the most recento Trees may be scaled to geological time Look at where the latest common ancestor for the group is.Tree of LifeOlder way of grouping life- 2 kingdom system-Linnaeuso Animals- animals and unicellular motile protozoanso Plants-fungi, bacteria, algae, unicellular organisms- 5 kingdom- Whitakero Monera-bacteria and archaeo Animalso Plantaeo Fungio Protista- Current 3 domain systemo Eukaryao Archaeao BacteriaThere was a common ancestor for ALL life (LUCA)Horizontal gene flow was likely in early organismsMitochondrion develop into chloroplastsSome see the tree with tangled


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TAMU BIOL 112 - CH26

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