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Worm-like Animals

Worm-like Animals. Characteristics. Invertebrates. Cephalization. Sense organs and nerve cells located at anterior end. Coelom. Characteristics. Phylum Platyhelminthes “Flatworms”. Flattened with no coelom. Unsegmented. No circulatory or respiratory system.

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Worm-like Animals

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  1. Worm-like Animals

  2. Characteristics • Invertebrates. • Cephalization. • Sense organs and nerve cells located at anterior end. • Coelom.

  3. Characteristics

  4. Phylum Platyhelminthes“Flatworms” • Flattened with no coelom. • Unsegmented. • No circulatory or respiratory system. • Digestive cavity with one opening. • Mostly parasitic. • 1 mm to 5 m in length.

  5. Phylum Platyhelminthes Class Cestoda • Parasitic tapeworms. • Suckers and hooks attach tapeworm to intestines. Watch This!!!

  6. Phylum Nematoda“Roundworms” • Unsegmented cylindrical bodies. • Pseudocoelom. • Complete digestive tract. • No circulatory or respiratory system. • Mostly parasitic. • 2 mm to 2 m in length. Watch This!!!

  7. Phylum Nematoda

  8. Phylum Annelida“Segmented Worms” • Segmented bodies. • Presence of a coelom. • Complete digestive tract. • Has a circulatory system. • Gas exchange via gills or skin.

  9. Phylum Annelida • Many have bristles on outer surface to aid with movement. • 0.5 mm to 3 m in length. • E.g., Earthworms and leeches. Watch This!!!

  10. Phylum Mollusca

  11. Characteristics Soft-bodied. Coelom. Two body openings. Bilateral symmetry.

  12. Body Plan Three unsegmented body parts: Foot: Locomotion and feeding. 2. Mantle: Wraps around body and secretes shell. In some, shell may be reduced or absent. 3. Visceral Mass: Internal Organs.

  13. Body Plan

  14. Body Plan Complete digestive and circulatory system. Gills for respiration. <1 cm to 20 m in length.

  15. Class Bivalva E.g., clams, oysters, scallops & mussels. Hinge connects two shells. Primarily sessile. Foot may be modified to burrow. No head. Filter feeders. 0.5 mm to 1.4 m in size. Watch This!!!

  16. Class Gastropoda E.g., snails and slugs. Foot used for locomotion. Respiration through gills and moist skin. Spiral shell except for slugs. 0.5 mm to 75 cm in size. Watch This!!!And This!!!

  17. Class Cephalopoda E.g., squids and octopi. Shell reduced to internal rod. Only mollusk with closed circulatory system. Tentacles with suckers. Well-developed brains; capable of learning. Move via jet propulsion (by funnel). 10 mm to 20 m in size.

  18. Class Cephalopoda Watch This!!!And This!!!

  19. Phylum Echinodermata

  20. Phylum Echinodermata E.g., sea stars, sea urchins, sand dollars and sea cucumbers. Larvae: Bilaterally symmetrical. Adults: Radially symmetrical around 5+ arms.

  21. Phylum Echinodermata Complete digestive system. Simple circulatory and nervous system. No respiratory or excretory system. No head. Endoskeleton with spiny projections. Watch This!!!

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