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Unraveling Diversity: Taxonomy and Evolutionary Systematics

Explore the classification and relationships of organisms through taxonomy and evolutionary systematics. Learn about binomial nomenclature and molecular taxonomy to understand biodiversity and phylogeny. Discover the significance of monophyletic and paraphyletic taxa.

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Unraveling Diversity: Taxonomy and Evolutionary Systematics

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  1. Chapter 22 Understanding Diversity:Systematics

  2. Systematics • Diversity of organisms • Evolutionary relationships • Biodiversity • The variety of organisms • The ecosystems they form

  3. Taxonomy • Naming • Describing • Classifying • Classification • Grouping organisms by their similarities or relationships

  4. Binomial nomenclature • Genus + specific epithet • Homo sapiens • Quercus alba • Linnaeus, mid-18th century • Facilitates international science

  5. Taxonomic categories • Kingdom • Phylum • Class • Order • Family • Genus • Species

  6. Taxonomic Categories

  7. Six Kingdoms • Based on cell structure & nutrition • Archaebacteria • Eubacteria • Protista • Fungi • Plantae • Animalia

  8. Six Kingdoms

  9. Three domains • Based on molecular differences • Archae • Lack simple RNA polymerase • Eubacteria • Peptidoglycan in cell walls • Eukarya • Eukaryotes

  10. Three Domains

  11. Phylogeny • Evolutionary history of a group of organisms from a common ancestor • Classifications based on common ancestors • Traditionally based on structural similarities

  12. Homology • Structure derived from a recent common ancestor • Wing bones in birds and bats • Homoplasy • Superficially homologous but independently acquired • Body form in sharks and dolphins

  13. Plesiomorphic characters • Shared ancestral characters • Distant common ancestor • Synapomorphic characters • Shared derived characters • More recent common ancestor

  14. Molecular systematics • Determines evolutionary relationships by comparing macromolecules • Ribosomal RNAs 5S, 16S, 23S • Transcribed from highly conserved DNA regions • Mitochondrial DNA

  15. Molecular taxonomy

  16. Molecular clocks • Measure time since divergence from a common ancestor by the number of differences in nucleotide or protein sequences • Rate of change must be constant

  17. Monophyletic taxon • All descendants of most recent common ancestor • Mammals • True evolutionary relationships • Clade

  18. Paraphyletic taxon • Common ancestor but not all descendants • Class Reptilia does not include birds even though they share a recent common ancestor • Avoided by cladistic systematists

  19. Monophyletic and paraphyletic taxa

  20. Polyphyletic group • Does not share recent common ancestors • Protista • Shares homoplastic features • Misrepresents evolutionary relationships

  21. Polyphyletic groups

  22. Evolutionary systematics • Evolutionary branching • Extent of divergence • Structural and other changes • Combination of shared ancestral characters and shared derived characters

  23. Evolutionary systematics

  24. Cladistics

  25. Cladistics • Emphasizes common ancestry over phenotypic similarity • Only shared derived characters • Cladograms • Parsimony guides choices

  26. Using parsimony to evaluate hypotheses

  27. Outgroup analysis • Separate ancestral and derived characters • Outgroup taxon diverged earlier than others • Outgroup represents the ancestral condition

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