Chapter   16 - ANIMAL CLASSIFICATION, PHYLOGENY, AND ORGANIZATION


CLASSIFICATION of ORGANISMS


A TAXONOMIC HIERARCHY

  1. Carolus Linnaeus (1707-1778)
  2. more on classification from the University of Minnesota, General Zoology

MAJOR DIVISIONS OF LIFE

Molecular Approaches to Systematics
comparing DNA and RNA sequences
Ribosomal RNA
         evolutionary conservation

Three Domains: Eubacteria, Archaea, Eukarya [fig. 16.2b]

 


ANIMAL SYSTEMATICS

Arranging Organisms into Groups  [fig 16.3]

Using the Evidence of Evolution: Classifying life.  A great overview from Kimball's Biology Pages

Philosophies of Classification

  1. Numerical Taxonomy:
  2. Evolutionary Taxonomy:
    1. phylogenetic tree of vertebrate phylogeny (Fig. 16.4)
  3. Phylogenetic Systematics (cladistics)
    1. clade: a monophyletic group
    2. cladogram (Fig. 16.5)
      1. a branching diagram displaying evolutionary relationships
    3. To learn more
    4. Cladistic Terminology
      1. monophyletic:
      2. paraphyletic
      3. polyphyletic:
      4. synapomorphy:
      5. clade
    5. try this exam from Dr. David Altoff, Vanderbilt University

Evolutionary Relationships and Tree Diagrams

cladogram showing vertebrate phylogeny (Fig. 16.6)


PATTERNS OF ORGANIZATION

ANIMAL SYMMETRY [Table 16.2]


OTHER PATTERNS OF ORGANIZATION

  1. Unicellular (Cytoplasmic) Organization
    1. "cytoplasmic" grade
      • unicellular, includes most protozoans - all functions within a single cell
    2. cellular grade
      • aggregate of cells
        • division of labor e.g. Volvox
        • somatic and reproductive cells
      • perhaps sponges (which are multicellular, but with no germ layers or true tissues, extracellular digestion)
  2. Eumetazoa: tissues and organs present
    1. germ layers: three embryonic tissues [Table 10.1]
      • tissues derived from the 3 germ layers-figure from Loyola University
        1. ectoderm: outer embryonic layer - skin and nervous tissue
        2. endoderm: inner embryonic layer - lines digestive tract
        3. mesoderm: middle embryonic layer - muscles, bones, circulatory system, organs
    2. diploblastic Organization [fig 16.10]: ectoderm and endoderm separated by a noncellular mesoglea
      • cell-tissue grade: aggregations of similar cells into definite patterns or layers
      • Cnidaria
    3. Triploblastic Organization [fig 16.11]:
      • three germ layers are present
      • bilateria: bilateral symmetry (may be lost)

BODY CAVITIES

acoelomate - left
pseudocoelomate - center
eucoelomate - right
Red = ectoderm
Yellow = endoderm
Blue = mesoderm

Image courtesy of BIODIDAC

 
  1. acoelomates:
    1. no body cavity [fig. 16.11a]
    2. body double-walled sac surrounding digestive cavity
    3. single opening to outside
    4. characteristic of flatworms.
  2. coelom
    • tube within a tube = body cavity
    • Illustrations from UT Biology 301
    •  advantages
      1. body cavity allows more room for organs in fluid filled cavity with no pressure from muscles
      2. cavity can serve as circulatory system
      3. more efficient and longer digestive system
      4. more room for gonads, gametes, etc.
      5. can function as a hydrostatic skeleton.
    1. Pseudocoelomate [fig 16.11b]
      1. body cavity between mesoderm and endoderm (cavity from blastocoel)
      2.  characteristic of roundworms
    2. Eucoelomate) [fig. 16.11c]
      1. body cavity completely lined with a thin mesodermal sheet (outer peritoneum and inner serosa

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