Chapter 26 Phylogeny and the Tree of Life Classification and Phylogeny Linnaean 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 Taxonomy o Groups taxa are based on similarities and differences But it is very subjective Linnaeus s hierarchical classification system is nested o Groups of lower taxa species genus form higher taxa All species in any taxon share certain features Phylogenetic Trees Phylogeny is the evolutionary history of a species and its relationship to other species o 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 time Systematics Systematics is the overall study of phylogenetic relationships Based on homologies o Of morphology 26 11 o Of DNA sequences 26 8 But morphological differences can be much greater than DNA differences o 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 ancestors Systematics Cladistics Purpose Hypothesize phylogeny in the form of a dichotomous tree 2 branches Method Identify characteristics as ancestral or derived o Create the most parsimonious tree based on shared derived characteristics synapomorphies Interpreting cladistic tree clado branch o Clade all the species on a branch o All species in a clade share homologies The more shared derived characteristics the closer the relationship o Infer the sequence of evolutionary events Characteristics shared by all are the earliest in history Unique characteristics are the most recent o Trees may be scaled to geological time Look at where the latest common ancestor for the group is Tree of Life Older way of grouping life 2 kingdom system Linnaeus o Animals animals and unicellular motile protozoans o Plants fungi bacteria algae unicellular organisms 5 kingdom Whitaker o Monera bacteria and archae o Animals o Plantae o Fungi o Protista Current 3 domain system o Eukarya o Archaea o Bacteria There was a common ancestor for ALL life LUCA Horizontal gene flow was likely in early organisms Mitochondrion develop into chloroplasts Some see the tree with tangled roots
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