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CHAPTER 17 – CLASSIFICATION OF ORGANiSMS

17-1: Biodiversity 17-2: Systematics 17-3: Modern Classification. CHAPTER 17 – CLASSIFICATION OF ORGANiSMS. Biologists have named and classified almost 2 million species

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CHAPTER 17 – CLASSIFICATION OF ORGANiSMS

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  1. 17-1: Biodiversity 17-2: Systematics 17-3: Modern Classification CHAPTER 17 – CLASSIFICATION OF ORGANiSMS

  2. Biologists have named and classified almost 2millionspecies Over time, scientists have created various systems of classification to organize their knowledge of the tremendous # of species each system places species into categories based on particular characteristics 17-1: Biodiversity

  3. Biodiversity • The variety of organisms considered at all levels from populations to ecosystems • # of ID’d species - increased over time • 100s to millions • Terry Erwin (1980s) • Catalogued insect species in tropical rain forest • Found over 1000 species in only 19 trees • Estimate more than 30 million species on Earth Classifying organisms

  4. Every year, biologists discover 1000s of new species and seek to classify them in a meaningful way • Proposed + modified as scientific understanding increases • Ex. – the pangolin • Grouped with lizards + crocodiles due to scales? • Grouped with animals that use sticky tongues to eat ants? Classifying organisms

  5. Taxonomy • The science of describing, naming, + classifying organisms • Taxon • Any particular group within a taxonomic system • Over time, many different schemes have been developed Taxonomy

  6. Aristotle • Classified organisms in 2 taxa: • Plants • Grouped them based on stemdifferences • Animals • Grouped them based on where they lived: • Land, water, or air Taxonomy

  7. Aristotle’s system was inadequate • Common names were not useful either • Ex. Robin or Fir tree • Vary from place to place • More than one common name • Don’t accurately define a species (i.e. Jellyfish) Taxonomy

  8. Carolus Linnaeus • System that grouped organisms into hierarchicalcategories according to their form + structure(morphology) • System had 7 levels The linnaean system

  9. Kingdom Phylum Class Order Family Genus Species Levels of classification

  10. Linnaeus gave an organism a species name, or scientific name, with two parts: • Genus • Species identifier • Examples: • Homo sapiens • Chaos chaos • Thamnophismelanogaster • Drosophila melanogaster Binomial nomenclature Binomial nomenclature

  11. Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapiens Your classification

  12. Subspecies • Species that live in different geographic areas • Example: • Terrapenecarolinatriungui Binomial nomenclature

  13. Classification video

  14. Modern biologists consider not only the VISIBLESIMILARITIES but also similarities in: • Embryos • Chromosomes • Proteins • DNA • Systematics • Goal is to classify organisms in terms of their natural relationships • organize in context of evolution 17-2: Systematics

  15. Systematic taxonomists agree that an organism’s classification should reflect PHYLOGENY(evolutionary history) • Phylogenetics • The analysis of the evolutionary or ancestral relationships among taxa. phylogenetics

  16. Use comparisons to classify: • Living species vs. fossils • Embryonic development + gene expression • Chromosomes or macromolecules (DNA/RNA) phylogenetics

  17. Represent hypotheses by a phylogenetic tree (diagram) • Branching pattern indicates how closely related a subset of taxa are thought to be • May be revised with new discoveries or evidence phylogenetics

  18. Biologists use fossils as important clues for the timing of evolutionary changes + divergence • The fossil record my lack evidence… • May also compare… • Homologous features (jaws of pangolin + dogs) • Analogous features (scales of snakes + pangolin) • Embryology (amnion) • The greater the # of features shared by organisms, the more closely related the organisms are Evidence of shared ancestry

  19. 1966 – WilliHennig • Cladistics • A system of phylogenetic analysis that uses shared+ derivedcharacters as the only criteria for grouping taxa • Shared– feature that all members of a group have in common • Ex. Hair in mammals or feathers in birds • Derived– feature that evolved only within the group • Ex. Feathers Cladistics

  20. Cladistics assume that organisms share one or more derived characters • Probably inherited them from an common ancestor • Group known as a “clade” • Includes its ancestors + all descendants • No other categories (i.e. order, class, etc..) • Creates a cladogramto show their hypothesis Cladistics

  21. Example - A cladogram

  22. Out-group • Organism that is only distantly related to the other organisms • Acts as a starting point for comparisons Constructing a cladogram

  23. Biologist can count the shared, derived amino acids at each position in a protein to make a cladogram Molecular cladistics

  24. “Molecular Clock” • A tool for estimating the sequence of past evolutionary events • Suggests that the greater the differences between a pair of sequences, the longer ago those two sequences diverged from a common ancestor Molecular cladistics

  25. If two species have the samebandingpattern in regions of similarchromosomes, the regions are likely to have been inherited from a single chromosome in the last common ancestor of the two species chromosomes

  26. To classify an organism and represent its systematics in an evolutionary context, biologists use many types of information to build and revise phylogenetic models: • Physical features • Embryos • Genes in nucleus • Mitochondrial DNA • Ribosomal RNA Putting it all together

  27. Taxonomists have revised two Linnaean-inspired categories • Domains • Kingdoms 17-3: modern classification

  28. Based on cell types, scientists can divide all life into two groups: • Eukaryotes • Prokaryotes • Carl Woese - 1977 • Proposed major revision of 6 kingdom system • Compared rRNA sequences of different organisms and grouped them according to their similarities The tree of life

  29. Insights from rRNA analyses: Data is consistent with hypotheses that all living organisms inherited their rRNA genes from ancient organisms or form of life All living things can be grouped into 1 of the 3 domains: BACTERIA, ARCHAEA, or EUKARYA Species in domain ARCHAEA are greatlydifferent than bacteria Three domains of life

  30. Small, single-celled prokaryotes • Have cell walls • Contain peptidoglycan • Reproduce by binary fission • One circular chromosome Domain bacteria

  31. Have distinctive cell membranes • Made of hydrocarbons, not fatty acids • Some are autotrophic (chemosynthesis) • May inhabit harsh environments Domain archaea

  32. Consists of eukaryotic organisms • Includes plants, animals, fungi, + some single-celled organisms Domain eukarya

  33. The 6 kingdoms are more of a traditional taxonomic system • Kingdoms: • Eubacteria • Archaebacteria • Protista • Fungi • Plantae • Animalia Six kingdoms

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