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Phylogeny and the Tree of Life

Phylogeny and the Tree of Life. Phylogeny -evolutionary history of a species Systematics- study of biological diversity in an evolutionary context. Phylogenetic Tree. Phylogeny and Systematics. Goal of systematics-biological classification should reflect phylogeny

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Phylogeny and the Tree of Life

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  1. Phylogeny and the Tree of Life Phylogeny-evolutionary history of a species Systematics-study of biological diversity in an evolutionary context

  2. Phylogenetic Tree

  3. Phylogeny and Systematics • Goal of systematics-biological classification should reflect phylogeny • Taxonomy-binomial nomenclature • Monophyletic taxon-single ancestor gave rise to all species in a taxon • Polyphyletic taxon-members are derived from two or more ancestral groups (plants from vascular and mosses) • Papraphyletic taxon-excludes species that share a common ancestor that gave rise to the species included in the taxon (birds and reptiles)

  4. Homology-likeness attributed to shared ancestry Analogy-similarities due to convergent evolution Convergent evolution-acquisition of similar characteristic in species due to sharing similar ecological roles Homology and Analogy

  5. Molecular Biology and Systematics • Molecular comparisons of proteins and DNA • Comparisons are objective and quantitative

  6. DNA, RNA and Protein Comparisons • DNA hybridizations-compare degree of similarity between two species • Restriction maps • DNA sequence analysis • Homologous DNA sequences-mutations accumulate as species diverge • Molecular clocks-number of amino acid substitutions is proportional to the elapsed time since divergence

  7. Jurassic Park? • Fossilized DNA has been isolated from 17 million year old magnolia leaves, 40,000 year old mammoth, and 65 million year old t. rex. • Problem-contaminated with fungus

  8. Two Aproaches to Phylogentic Systematics • Phenetics-decides taxonomic affinities on measurable similarities and differences. • Cladistics-classifies organisms according to the order in time that taxonomic groups diverge.

  9. Cladistics Primary criterion is common ancestory clades-ancestral species with all of its descendents Monophyletic, paraphyletic, and polyphyletic groupings

  10. Phylogenetics-Problems? • Accepts only monophyletic origins-consequences? • Birds and reptiles……………..

  11. Websites and Videos • http://www.youtube.com/watch?v=dK3O6KYPmEw

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