Chapter 3 Outline

HEIRARCHY

• ATTRIBUTES OF LIVING ORGANISMS CAN BE ORGANIZED INTO A HEIRARCHY
  • HIERARCHICAL DISTRIBUTION OF FEATURES IS THE MOST FUNDAMENTAL PROPERTY OF THE BIOTA, I.E. ALL LIVING ORGANISMS THAT HAVE POPULATED THE EARTH
    • e. g., all organisms possessing fur (mammals) are a subset of all organisms with backbones (vertebrates) which are a subset of all living organisms
• CHARACTERS
  • ISOLATED OR ABSTRACTED CHARACTERISTIC OF AN ORGANISM
  • CHARACTER ACQUIRES MEANING WHEN ITS DISTRIBUTION AMONG A SELECTED GROUP OF ORGANISMS IS CONSIDERED
    • e. g., possessiom of retractile claws is a characteristic of the group Felidae (cats), including domesticated cats, bobcats, lions, jaguars and extinct saber-toothed tigers
  • POSITION IN THE HIERARCHIY IS OF GREAT SIGNIFICANCE
    • e. g., possession of feathers is characteristic of all birds and distinguishes birds from nonbirds; however, different birds must be distiguished based on characters other than feathers
  • GENERAL VS SPECIFIC CHARACTERS
    • Specific characters characterize all members of a group
    • General characters characterize a larger group
    • e. g., possession of two eyes is a general character among humans (and among all vertebrates) and cannot be used to distinguish different humans, or for that matter a human from a frog; however, possession of two eyes is a specific character for distinguishing vertebrates from nonvertebrates
• CLADOGRAMS
  • BRANCHING DIAGRAMS USED TO DEPICT THE HIERARCHICAL DISTRIBUTION OF SHARED CHARACTERS
  • USES OBSERVABLE FEATURES, NOT FUNCTIONS
  • ARRANGEMENT OF CHARACTERS ON CLADOGRAM IS CONTROLLED BY CHOICE OF CHARACTERS
  • CLADISTIC ANALYSIS HAS PROVEN TO BE A POWERFUL TOOL FOR STUDYING EVOLUTIONARY RELATIONSHIPS AMONG ORGANISMS

ORGANIC EVOLUTION

• PHYLOGENY - HISTORY OF DESCENT OF ORGANISMS
• CLADES = MONOPHYLETIC GROUPS = NATURAL GROUPS
  • GROUPS OF ORGANISMS IN WHICH MEMBERS OF EACH GROUP ARE MORE CLOSELY RELATED TO EACH OTHER THAN TO ANY OTHER CREATURE
  • MEMBERS SHARE A MORE RECENT COMMON ANCESTOR WITH EACH OTHER THAN WITH ANY OTHER ORGANISM
• DESCENT WITH MODIFICATION
  • MODERN ORGANISMS ARE EXTREMELY VARIED
  • ANCIENT ORGANISMS HAVE VARIED THROUGH TIME
  • LATER ORGANISMS HAVE DESCENDED & MODIFIED FROM EARLIER FORMS
• JEAN BAPTISTE DE LAMARCK
  • 1ST ACCEPTED THEORY OF ORGANIC EVOLUTION ­ INHERITANCE OF ACQUIRED CHARACTERISTICS
    • organism acquires traits during lifetime & passes them on to descendants
• CHARLES DARWIN & ALFRED R. WALLACE
  • PROVIDED THE KEY CONCEPT: EVOLUTION PROCEEDS THROUGH NATURAL SELECTION ("THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION"; 1859)
    • 1. there is natural variation among the individuals of a given species
    • 2. some variations are more favorable than other variations
    • 3. organisms produce many offspring that die before maturity
    • 4. individuals surviving to reproduce must be those with the most successful combinations of variable characteristics
• EVIDENCE FOR ORGANIC EVOLUTION
  • EMBRYOLOGY
    • similarities early in development (tails in humans); divergence in later stages
  • COMPARATIVE ANATOMY
    • homologous structures, e. g., tetrapod limbs modified to wings or fins, as opposed to analogous structrures, e. g., bird/bat wings vs. fly wings
    • vestigial organs [non or partially funtional organs], e. g., horse toes & mammalian dewclaws, whale & snake pelvises, human appendix & wisdom teeth
  • BIOCHEMISTRY
    • DNA, activator genes, ADP, blood proteins
  • SMALL SCALE EVOLUTION
    • industrial melanization
    • insecticide/antibiotic resistance
  • FOSSILS
    • fossils are observed to change through time
      • SIMPLEST & LEAST SIMILAR TO MODERN IN OLDEST ROCKS
      • COMPLEX & MOST SIMILAR TO MODERN IN YOUNGER ROCKS
  • HIERARCHICAL DISTRIBUTION OF CHARACTERS AMONG ORGANISMS
• CLADOGRAMS AND THE RECONSTRUCTION OF PHYLOGENY
  • TREE OF LIFE = THE SINGLE PHYLOGENY THAT DOCUMENTS THE INTERRELATEDNESS OF ALL LIFE
  • CLADOGRAMS ARE USED TO DELINEATE BRANCHES ON THE TREE OF LIFE
  • ORGANISMS THAT ARE CLOSELY RELATED SHARE SPECIFIC FEATURES
    • Specific Characters = Derived (aka advanced)
    • General characters = Ancestral (aka primitive)
    • Only derived characters provide evidence of monophyletic groups
• PARSIMONY
  • CLADOGRAMS ARE HYPOTHESES OF RELATIONSHIP
  • WITH A GIVEN SET OF CHARACTERS, IT MAY BE POSSIBLE TO CONSTRUCT SEVERAL POSSIBLE CLADOGRAMS
  • DIFFERENT HYPOTHESES OF RELATEDNESS CAN BE DISTINGUISHED BY THE PRINCIPLE OF PARSIMONY
  • THE SIMPLEST CLADOGRAM, THE ONE WITH THE FEWEST EVOLUTIONARY EVENTS, IS THE PREFERRED CLADOGRAM ACCORDING TO PARSIMONY
• SCIENCE & TESTING HYPOTHESES
  • SCIENCE IS AN APPROACH TO CERTAIN KINDS OF ISSUES ROOTED IN A PARTICULAR TYPE OF LOGIC
  • AN HYPOTHESIS IS PROPOSED AND TESTED
    • The hypothesis is rejected if it is falsified
    • The hypothesis is never really proved - just not falsified
  • CLADOGRAMS CAN BE TESTED BY ADDING CHARACTERS
    • The cladogram is rejected if it is not the most parsimonious
    • Robust cladograms have survived many falsification attempts