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Taxonomy. J.T. II Olivar, MAEd Faculty of Arts and Letters University of Santo Tomas. Outline of the Lecture. The Categorization of Earth’s Living Things Constructing Evolutionary Histories: Classical Taxonomy and Cladistics. The Categorization of Earth’s Living Things.

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J.T. II Olivar, MAEd

Faculty of Arts and Letters

University of Santo Tomas

Outline of the lecture
Outline of the Lecture

  • The Categorization of Earth’s Living Things

  • Constructing Evolutionary Histories: Classical Taxonomy and Cladistics

The categorization of earth s living things
The Categorization of Earth’s Living Things

  • Taxonomic Classification and the Degree of Relatedness

    A. How to name a species

    • Specificity – each name must indicate one type of organism

    • Universality – Latin used to avoid confusion caused by common names

      • Recognizable by biologists of all nations

    • Binomial nomenclature

      • First names identifies groups of closely related species

      • Second name identifies specific species

B. Genus name

  • Indicates a group of species that share common features

  • “Relatedness” determines which species belong in which genus

    • Indicates a common ancestor at some time

    • Could be millions of years in the past

  • Systematics – branch of biology studying evolutionary history of organisms

C. Taxonomic System

  • Uses eight categories to catalog every identified organism

    • In order from most to least specific – species, genus, family, order, class, phylum, kingdom, domain

  • Taxon – organisms in each category

  • A Taxonomic Example: The Common House Cat

    • Genus: Felis – contains eight other living species

    • Family: Felidae – contains other 14 genera

    • Order: Carnivora – includes all meat-eating organisms

    • Kingdom: Animalia – includes all animals

    • Each level up the ladder includes more organisms

Constructing evolutionary histories classical taxonomy and cladistics
Constructing Evolutionary Histories: Classical Taxonomy and Cladistics

  • Classical Taxonomy Looks for Similarities

    • Classical taxonomy uses morphology to judge similarities

      • Compare physical form of fossil organisms with modern ones

      • Examine skull shape, teeth patterns (dentition), limb structure, etc.

      • Also compare geographic locations

      • Modern taxonomy includes relatedness of DNA and protein sequences

  • Obscuring the trail: Convergent evolution Cladistics

    • Similar features may arise independently in response to environment

      • Homologies – common structures from shared ancestor

      • Analogy – structures that appear similar in appearance or structure without common ancestry

    • Convergent evolution

      • Separate evolutionary lines shaped in similar ways

      • Caused by similar environmental pressures

  • Another System for Interpreting the Evidence: Cladistics Cladistics

    • Cladistics – method to establish relatedness

      • Core of modern phylogenetic work

      • Cladogram – diagram of lines of descent and order of branches

        • Seeks to answer – which organisms have most recent common ancestor

  • Cladistics employs shared ancestral and derived characteristics

    • Ancestral characters

      • Characteristics present in common ancestor

      • Ex: dorsal vertebral column in vertebrates

    • Derived character

      • Characteristic not shared by all organisms descended from common ancestor

  • Assumption characteristics

    • Closely related animals share more derived characteristics than those not closely related

  • Uses the hagfish as reference organism for all mammalian carnivores

    • Outgroup – does not share ancestral characters

      • Reference point for derived characters

  • Should Anything but Relatedness Matter in Classification? characteristics

    • Reconciling classical taxonomy with cladistics

      • Classical groupings uses more than evolutionary relationships

        • Considers many special qualities shared by organisms

        • Concerned with lines of descent and evolutionary relationships

      • Cladistics uses phylogeny to place organisms on tree

        • Concerned most with establishing lines of descent