Bio1151 Chapter 26 Phylogeny and The Tree of Life
  1.            is the study of the evolutionary history and relationships of organisms, based on shared          characters inherited from a common           .

      What are the evolutionary relationships among a human, a mushroom, and a tulip? Despite appearances, molecular evidence has revealed that animals, including humans, and fungi, such as mushrooms, are more closely related to each other than either are to plants.
     
     
     
     
  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 species are placed into groups belonging to more comprehensive groups (taxa). Starting from the most comprehensive taxon, Linnaeus classified organisms into kingdom, phylum, class, order, family, genus, and species. Leopards and humans both belong to kingdom Animalia, phylum Chordata, but 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.


      Each group in this hierarchy of organisms is a clade (taxon) with shared derived characters. For example, animals in order Carnivora posses carnassials : the last upper premolars and the first lower molars adapted for shearing food a scissor-like manner. 01_14ClassifyingLife_L.jpg-->
     
     
     
     
  3. Phylogenetic relationships are shown as branching trees where each branch point represents the             of two       when they shared a common           (homology).

      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. ../ch24/24_02bBioSpeciesConceptB-U.jpg-->


      Each group in this hierarchy of organisms is a clade (taxon) with shared derived characters. For example, animals in order Carnivora posses carnassials : the last upper premolars and the first lower molars adapted for shearing food a scissor-like manner. 01_14ClassifyingLife_L.jpg-->


      A phylogenetic tree shows evolutionary relationships by homology. A homology is a shared derived character, such as hair among the mammals, inherited from a common ancestor.
     
     
     
     
    •                similarity can be misleading due to             evolution (analogy).

        Similar environmental pressures and natural selection can produce similar (analogous) adaptations in organisms from different evolutionary lineages: convergent evolution An elongated body, large front paws, small eyes, thicken skin, and a tapered nose all evolved independently in the marsupial Australian mole and eutherian North American mole.


        Convergent evolution. The sugar glider is a marsupial mammal (young finish development in a pouch) that evolved in Australia. While sugar gliders superficially resemble the eutherian flying squirrels of North America, the ability to glide through the air evolved independently in these 2 distantly related mammals. 22_17ConvergentEvolution.jpg-->
       
       
       
       
    •            homologies that make use of computer programs to analyze      segments can reveal many relationships not attainable by other methods.


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

      A character table can show shared derived characters inherited among organisms. A 0 indicates a character is absent; a 1 indicates that it is present. The shared derived characters can be arranged 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 constitues a shared derived character (homology) for the clade (ingroup). An outgroup does not possess that character.
     
     
     
     
  5. A clade must be               , and consists of the           species and all its descendants; paraphyletic and polyphyletic groups do not qualify as legitimate clades.

      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: it consists of an ancestor (X) and some (D, E, F), but not all (excludes G), of that ancestors descendants.


      Polyphyletic. Group III is polyphyletic: it lacks a common ancestor of all the species in the group.
     
     
     
     
  6. The tree of life is divided into three great clades called          :           (Monera),          , and          .

      The tree of life. Based on rRNA gene sequences, living organisms are divided into 3 domains: Bacteria, Archaea, and Eukarya. Eukarya and Archaea appear to share a common ancestor, 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 clade.