Primitive Invertebrates

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Chapter 39

• Primitive Invertebrates

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Animal Kingdom

• SubKingdom-Parazoa
• PhylumPorifera
• Sponges lacks symmetry

• Subkingdom Eumetazoa
• Radially Symmetrical-Phylum-Cnidaria
• Phylum-Ctenophera
• Bilaterally-Symmetrical ?

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Bilaterally Symmetrical Animals
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Bilateral Symmetry
Chapter 5

• Fig. 5.14 Plane of symmetry in a bilaterally
  symmetrical animal.

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Radial Symmetry
Chapter 5
Fig. 5.8 Planes of symmetry in a radially
symmetrical animal.

• Fig. 5.9 (Top) Undischarged nematocyst (Bottom)
  Discharged penetrant nematocyst.

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Body Cavities
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Acoelomates

• Phylum Platyhelminthes Flatworms
• Characterisitcs
• 1 opening for digestion
• Free living phagocytosis
• Parasitic absorb nutrients through cell
  membrane.
• No circulatory system
• Nervous system 2 ganglias 2 nerve cords
• Examples Planaria, tapeworm flukes.

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Acoelomates (Continued)

• Phylum- Rhynchocolea- Ribbon Worms
• Similar to flatworms
• Complete digestive system
• Closed circulatory system.

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Pseudocoelomates

• Phylum Nematoda
• Characteristics
• Found in marine freswater soil
• Many are parasites
• Complete digestive system with mouth anus.
• Reproduction is sexual
• Examples parasitic in man hookworms,
  pinworms,roundworms, trichinella

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Pseudocoelomates (continued)

• Phylum Rotifera Rotifers
• Characteristics
• Small aquatic with cilia at head region
• Free living
• Sexes are separate.