Lesson 1 - Animal Structure

• How is life organized in terms of complexity?

  From simple to complex
• What does each group in the hierarchical organization represent?

  More complexity than the preceding one
• What are the five grades of organization in animals?

  • Protoplasmic Grade
  • Cellular Grade
  • Tissue Grade
  • Organ Grade
  • System Grade
• What are unicellular groups in the protoplasmic grade?

  Simple eukaryotic organisms
• What functions do unicellular organisms perform?

  All basic functions of life in one cell
• What does protoplasm contain?

  Organelles with specialized functions
• Why is there diversity among unicellular groups?

  Due to varying subcellular components
• How many major phyla of living multicellular animals do zoologists recognize?

  34 major phyla
• What significant event occurred 600 million years ago?

  The Cambrian explosion
• What was the impact of the Cambrian explosion?

  All major body plans evolved rapidly
• What does the basic uniformity of all life derive from?

  Common ancestry and similar cellular construction
• What is the cellular grade of organization?

  Cells combined into larger aggregates
• How do cells in the cellular grade function?

  As specialized parts of the whole organism
• What does the division of labor in cells allow?


  Specialized tasks previously done by subcellular components
• What is the tissue grade of organization?


  Cells grouped into patterns or layers
• What is a coordinated unit of cells called?

  Tissue
• What type of animals are eumetazoans?

  Animals like cnidarians
• What characterizes the organ grade of organization?


  Tissues assembled into larger functional units
• What do organs consist of?


  More than one kind of tissue
• What is the system grade of organization?


  Several organs working together
• Which animal phyla are associated with the highest level of organization?

  Complex animal phyla like annelids
• What are the differences in animal body plans?

  • Grade of organization
  • Body symmetry
  • Number of embryonic layers
  • Number of body cavities
  • Embryonic development
• What is symmetry in animals?


  Balance of proportions and shape correspondence
• What are the types of animal symmetry?

  • Asymmetrical
  • Spherical
  • Radial
  • Bilateral
• What is asymmetrical symmetry?


  No symmetry present
• What is spherical symmetry?


  Divided into mirrored halves by any plane
• What is radial symmetry?


  Divided into similar halves by multiple planes
• What is bilateral symmetry?


  Divided into two mirror portions along a sagittal plane
• What advantage does bilateral symmetry provide?

  Better fitted for directional movement
• What is cephalization?


  Differentiation of a head region with nervous tissue
• What are the regions of bilaterally symmetrical animals?

  Anterior, posterior, dorsal, ventral, medial, lateral
• What is a body cavity?


  Internal space cushioning and protecting organs
• What is the dependence of body cavity formation on?

  Mesodermal pouch formation during gastrulation
• What are the types of body cavities?

  • Acoelomate: no body cavity
  • Pseudocoelomate: partial body cavity
  • Coelomate: true body cavity
• How do sponges relate to body cavities?

  They are acoelomate with no real body cavity
• What happens after blastula formation in sponges?

  Cells reorganize to form adult body
• What is the archenteron?


  The primitive gut formed during gastrulation
• What does the embryo have after invagination?

  Two cavities: gut and blastocoel
• What lines the inside of the gut?

  Endoderm
• What is the outer layer of cells called?

  Ectoderm