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Modern Taxonomy Reflects Evolutionary History


Modern Taxonomy Reflects Evolutionary History Section 15.4 Taxonomy Identification, naming, & classification of species Common names don t always work well, because ... – PowerPoint PPT presentation

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Title: Modern Taxonomy Reflects Evolutionary History

Modern Taxonomy Reflects Evolutionary History
  • Section 15.4

  • Identification, naming, classification of
  • Common names dont always work well, because they
    have different meanings in different areas.
  • For example, a tortoise might be called a gopher
    in Florida, but in Kansas, "gopher" might refer
    to either a ground squirrel or a pocket gopher.
  • Goals
  • assign universal scientific name to each known
  • Place groups of species into larger groups of
    related species.

Linnean System of Classification
  • Swedish botanist Carolus Linnaeus
  • System has 2 main characteristics
  • 2 part latin name for each species (binomial).
    The 1st part is the Genus name, the 2nd part is
    the species name.
  • Genus is capitalized, species is lower case
  • The whole name is in italics
  • Ex. African lion (Panthera leo)
  • Hierarchy of species into broader and broader
  • Lg ? Sm Sm? Lg

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  • Phylogenic Trees (Cladograms)
  • In a phylogenetic tree, each branch point
    represents a common ancestor of the species above
    that point. In this diagram, the branches are
    labeled to reinforce how taxonomy reflects the
    branching pattern of evolution.

  • Homologous structures are one of the best clues
    to assess how closely organisms are related.
  • Not all similar structures are inherited from a
    common ancestor.
  • Convergent evolution is a process in which
    unrelated species from similar environments have
    adaptations that seem very similar.
  • Similar adaptations that result from convergent
    evolution are called analogous structures.
  • For example, the wings of insects and those of
    birds are analogous, not homologous, flight
    equipmentthey evolved independently. And, they
    are built from entirely different structures.
    There is no evidence that insects and birds
    shared a common winged ancestor.

  • This cladogram shows how derived characters can
    be used to identify clades among certain
    vertebrates (animals with backbones). All the
    species shown here share a common ancestor that
    had a backbone. (Each clade is actually defined
    by several derived characters, not just one.)

  • The key rule in cladistics is that all of the
    organisms of a particular clade must share
    homologous structures that do not occur outside
    the clade.
  • These unique features that unite the organisms as
    a clade are called derived characters.
  • A phylogenetic diagram that specifies the derived
    characters of clades is called a cladogram.
  • For example, compare the animals in the cladogram
    in Figure 15-30. The horse, wolf, leopard, and
    house cat all have hair. This derived character
    unites a clade that doesn't include the turtle.

Comparing Classification Schemes
  • Two- and Three-Kingdom Schemes - Linnaeus divided
    all known forms of life between the plant and
    animal kingdoms.
  • A Five-Kingdom Scheme
  • Three Domains - This newer scheme recognizes
    three basic groups two domains of
    prokaryotesthe Bacteria and the Archaeaand one
    domain of eukaryotes, the Eukarya.

  • For many years, most biologists classified
    organisms according to a five-kingdom system.
    Based on molecular data, however, many biologists
    now prefer a three-domain classification. Within
    each domain there are multiple kingdoms (only
    listed here for Eukarya).