Bio1151 Chapter 26 Phylogeny and The Tree of Life
  1.            is the study of the evolutionary history and relationships of organisms.

    Phylogenetic relationships.

    Molecular evidence has revealed that animals and fungi share a more recent common ancestor than either do with plants.

    Thus kingdom Animalia and kingdom Fungi are more closely related to each other than either are to kingdom Plantae.

     
     
     
     
  2. Carolus Linnaeus introduced a system of           , for classifying species in seven hierarchical categories (taxa).

    Carolus Linnaeus published his Systema Naturae in 1758.

    This was the first scientific approach to classifying organisms.



    Traditional taxonomy uses a hierarchical classification where organisms are placed into progressively more restricted groups (taxa).

    Starting from the most comprehensive taxon, Linnaeus classified organisms into kingdom, phylum, class, order, family, genus, and species.

    Leopards and humans belong to kingdom Animalia, phylum Chordata, class Mammalia.

    While leopards are in order Carnivora, humans are in order Primates.

    A taxon above kingdom called domain was added after Linnaeus proposed these 7 levels.



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  3. Phylogenetic relationships are shown as branching trees where a branch point represents the divergence of two       when they shared a common           (homology).

    Binomial nomenclature.

    The scientific name of an organism uses a binomial nomenclature composed of its genus and specific epithet.

    Thus genus Panthera and specific epithet pardus uniquely identifies the leopard (Panthera pardus), and humans are Homo sapiens.

    The cat family, Felidae, is a sister taxon with other families in the order Carnivora, which is a branch of class Mammalia.



      The scientific name for humans is Homo sapiens (kingdom Animalia).

      The genus is Homo, while the specific epithet is sapiens.



    A phylogenetic tree shows evolutionary relationships by homology.

    A homology is a shared derived character, such as hair among the mammals.

    Each homology is inherited from a common ancestor.

     
     
     
     
    •                similarity can be misleading due to             evolution.

      Convergent evolution.

      Organisms from different evolutionary lineages may evolve similar (analogous) adaptations to similar environments; this is called convergent evolution

      Large front paws, small eyes, and a tapered nose all evolved independently in the marsupial Australian mole and eutherian North American mole.

       
       
       
       
    •            homologies can reveal many relationships not attainable by other methods.


    Identifying homologous DNA.

  4. Ancestral DNA segments from 2 species are identical.
  5. Deletion and insertion mutations shift these sequences as the 2 species diverge.
  6. Homologous regions no longer align.
  7. Homologous regions realign after a computer program adds gaps in sequence 1.
     
     
     
     
  8. Shared ancestry and shared          characters are drawn on a            to show evolutionary relationships; this practice is called             .

    Constructing a cladogram from a character table. A character table shows shared derived characters inherited among organisms. A 1 indicates a character is present; a 0 indicates that it is absent. The shared derived characters can be arranged as a cladogram to track descent from a common ancestor.


    A cladogram is used to track relationships by shared derived characters inherited from a common ancestor.

    Clades are defined by an evolutionary novelty at the branching point, which constitutes a shared derived character (homology) for the clade (ingroup).

    An outgroup does not possess that character.

     
     
     
     
  9. A clade must be               , and consists of the           species and all its descendants.

    Which group constitutes a clade? Monophyletic
  10. group? + yes.

    Paraphyletic

  11. group? + no.

    Polyphyletic

  12. group? + no.

      Monophyletic.

      Group I (species A, B, C) is a monophyletic group, or clade, made up of an ancestral species (X) and all of its descendant species.



      Paraphyletic.

      Group II is paraphyletic and is not a true clade.

      It consists of an ancestor (X) and some (D, E, F), but not all (excludes G), of that ancestor's descendants.



      Polyphyletic.

      Group III is polyphyletic and is not a true clade.

      It lacks a common ancestor of all the species in the group.

     
     
     
     
  13. The tree of life is divided into three great clades called          :           (Monera),          , and          .

    Tree of life.

    Based on rRNA gene sequences, organisms are divided into 3 domains: Bacteria, Archaea, and Eukarya.

    Eukarya and Archaea share a common ancestor, and are more closely related to each other than to Bacteria.

    Note: Archaea and Bacteria are "prokaryotes" that lack organelles such as a nucleus.

    The lack of organelles is not a shared derived character, thus "prokaryotes" do not constitute a monophyletic clade.