Chapter 23 - Animals: The Invertebrates

 

  1. Characteristics of animals

    1. multi-cellular, diploid
    2. heterotrophs, either consuming other organsims or absorbing nutrients from them
    3. require oxygen
    4. most reproduce sexually
    5. most are motile in at least part of their life cycle
    6. life cycle includes stages of embryonic development
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  3. Major groups of animal diversity

    1. 32 phyla exist
    2. 2 major groups of phyla
      1. invertebrates
      2. vertebrates
    3. animals grouped and classified based on several characteristics
      1. level of body organization (cellular, tissue, organ)
      2. type of symmetry (none, radial, bilateral) [Figure 23.3]
      3. cephalization (concentration of sensory organs in a head)
      4. type of gut (none, sac-like, tubular)
      5. type of body cavity (none, false, true) [Figure 23.4]
      6. segmentation (repeating body units)
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  5. Invertebrate phyla

    1. Sponges
      1. cells, but no tissues or organs
      2. no symmetry, cephalization, gut, or body cavity
      3. filter feeders [Figure 23.7]
      4. many have skeletons
    2. Cnidarians
      1. tissues, but no organ systems
      2. radial symmetry
      3. sac-like gut
      4. alternation of body forms
      5. have nematocysts
    3. Flatworms
      1. simple nervous system
      2. sac-like gut
      3. no body cavity
      4. are hermaphrodites
    4. Roundworms
      1. beginning of cephalization
      2. complete tubular digestive system
      3. false body cavity
      4. are cylindrical and tapered at both ends
      5. are notorious parasites
    5. Mollusks
      1. fleshy, soft body but most have a shell
      2. respiratory organs of gills or lungs
      3. have a radula (rasping) organ for feeding
      4. some have well developed eyes
    6. Segmented worms (annelids)
      1. complex organ system
      2. body segmented into repeating units
      3. most have bristles on each side of their body
    7. Arthropods
      1. segmented body, segments grouped into functional units
      2. hardened exoskeleton of chitin
      3. jointed appendages
      4. respiratory structures
      5. specialized sensory structures
      6. very diverse
    8. Echinoderms
      1. have a water vascular system
      2. metamorphosis of a bilateral larva to a radial adult
      3. skin is spiny

     


  6. © Carol L. Wymer, 2003