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Phylogeny and the Tree of Life Systematics: classifying organisms and determining their evolutionary relationships -taxonomy (classification) and phylogenetics (evolutionary history) Tools used to determine evolutionary relationships:1. Fossils2. Morphology (homologous structures)3. Molecular evidence (DNA, amino acids) Taxonomy – science of classifying and naming organisms-binomial nomenclature (Genus species)-domain – kingdom – phylum – class – order – family – genus – species (dear king Philip came over for great spaghetti) Phylogenetic tree – branching diagram that shows evolutionary history of a group of organisms-starts with an ancestral lineage-the branch point from the ancestral lineage represents the common ancestor of the end-resulting taxa-branch points = where lineages diverge-polytomy = an unresolved pattern of divergence-basal taxon = the one that stays the same as the original-sister taxa = next to each other on the tree ***practice constructing phylogenetic trees*** Cladogram: diagram that depicts patterns of shared characteristics among taxa-clade = group of species that includes an ancestral species + all descendants-shared derived characteristics are used to construct cladograms-monophyletic group, paraphyletic group, polyphyletic groups When constructing phylogenetic trees:-use character tables – lists the characters on the left and the taxa across the top-A 0 indicates a character is absent, while a 1 indicates a character is present-Branch lengths can represent genetic change-Branch lengths can indicate time-Principle of MAXIMUM PARSIMONY: use simplest explanation (fewest DNA changes) for tree – keep it simple-Molecular clocks: some regions of DNA appear to evolve at constant rates – can estimate date of past evolutionary events (ex: origin of HIV infection in humans = 1930s) on the tree of life there are 3 domains: Bacteria, Archaea, Eukarya
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