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Chapter 22

Chapter 22. Understanding Diversity: Systematics. Systematics Diversity of organisms Evolutionary relationships Biodiversity The variety of organisms The ecosystems they form. Taxonomy Naming Describing Classifying Classification

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Chapter 22

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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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