34-2 Animal Bodies

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34-2 Animal Bodies

• 3 structural features used to classify animals
• 1. Symmetry
• 2. Germ layers
• 3. Body cavities

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• Animal bodies range from those which have no
  body and lack tissues (sponges) to those that
  have tissues and body shape (most animals).

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1. Symmetry

• Symmetry
• (constant overall pattern of
  structure)

• a. Asymmetrical
• b. Radial
• c. Bilateral

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Symmetry
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A. Asymmetrical

• No symmetry (sponge)

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B. Radial

• Similar parts branch out from a central line
  (ex. Hydra)

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C. Bilateral

•      Two similar halves (most animals have
  this type of symmetry)
• dorsal upper surface
• ventral lower surface
• anterior head region
• posterior tail region
• right
• left

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Cephalization

• Bilateral symmetrical animals exhibit
  cephalization
•  Sensory and brain are in anterior region
•  Have a head
• As move through their environment, the head
  proceeds to sense danger, prey or mate

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Lab A21

• Sponge p.694
• Jellyfish p. 48
• Sea urchin p. 783
• Sea star p. 784
• Snail p.727

• Grasshopper p.765
• Crayfish p. 748
• Frog p. 821
• Lizard p. 852
• Sea cucumber p. 784
• Starfish p. 785

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2. Germ Layers

• Tissue type found in embryos of all animals
  except sponges.
• All body features, organs and tissues arise
  from a germ layer.
• All animals but cnidarians ( Jellyfish) and
  ctenophores ( relative) have 3 germ layers. The
  two listed here have only 2 germ layers.

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Germ Layers
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3. Body Cavities (coelom)

• a. Aids in movement by providing a firm
  structure against which muscles can contract
• b. Allows movement of exterior of body,
  gives more freedom of movement
• c. Fluid acts as medium to transport
  nutrients and wastes

• Fluid filled space between digestive tract and
  outer wall of body
• Flatworms lack a body cavity (tapeworms).

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Coelom
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Animal Diversity

• Similarities in body parts and patterns of
  development allow scientists to classify animals
  and hypothesize about their evolutionary history.
•   Animals on same branch are more closely
  related. Chordates more closely related to
  echinoderms
• Fig. 34-5 p. 672

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Invertebrates 10 phyla

• 1.Annelida earthworm
• 2.Arthropoda lobster, crab, spiders
• 3.Echinodermata starfish, sea star
• 4.Cnidarians hydra, jellyfish
• 5.Mollusca clams, snails, octopus, slugs,
  squids
• 6. Rotifera rotifers
• 7. Protista amoebas, paramecium, euglena

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Vertebrates 1 phylum

•   Phylum Chordata (chordates)
• has notochord firm, flexible rod of tissue
  located in dorsal part of body and has dorsal
  nerve cord
• in most vertebrates, the notochord forms
  backbone and dorsal nerve cord develops into the
  brain and spinal cord.

• Subphylum vertebrata
• 1. Chordata amphibians (frogs), reptiles (
  lizards), birds, mammals, fish