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Worms & Mollusks

Worms & Mollusks. Chapter 27. Flatworms. Phylum Platyhelminthes Bilateral symmetry All 3 germ layers Cephalization One digestive opening Acoelomate. 3 groups of flatworms. 1)turbellarians Class Turbellaria 2)flukes Class Trematoda 3)tapeworms Class Cestoda. turbellarians.

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Worms & Mollusks

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  1. Worms & Mollusks Chapter 27

  2. Flatworms Phylum Platyhelminthes Bilateral symmetry All 3 germ layers Cephalization One digestive opening Acoelomate

  3. 3 groups of flatworms • 1)turbellarians • Class Turbellaria • 2)flukes • Class Trematoda • 3)tapeworms • Class Cestoda

  4. turbellarians • Free living

  5. Flukes • Parasitic • Live in internal organs

  6. tapeworms • intestinal parasites of vertebrates, where they absorb predigested nutrients (they have no digestive tract).

  7. Roundworms • Phylum Nematoda • Bilateral symmetry • All 3 germ layers • Cephalization • 2 digestive openings • Pseudocoelomate • Most are parasitic

  8. Roundworms & Disease • Trichinosis (from undercooked pork) • Filarial worms (elephantiasis)

  9. Ascarid worms (intestine parasites) • Hookworms (25% of world population)

  10. Segmented worms • Phylum Annelida • Bilateral symmetry • All 3 germ layers • Cephalization • 2 digestive openings • Coelomate • segmented

  11. Classes • Oligochaeta • earthworm • Polychaeta • many bristled worms • Hirudinea • leeches

  12. Mollusks Phylum Mollusca Soft bodied invertebrates that usually have an internal or external shell. Bilateral symmetry All 3 germ layers Coelomates Cephalization 2 digestive openings “open” circulatory system

  13. Groups of Mollusks • 1)Gastropods: (class Gastropoda) snails, slugs, limpets, nudibranchs • Move using a muscular “foot”

  14. 2)bivalves: (class Bivalvia) clams, mussels, oysters, scallops • Have 2 shells held together by powerful muscles.

  15. 3)cephalopods: (class Cephalpoda) octopus, squid, cuttlefish, nautilus • Soft bodied mollusk with head atteched to foot. Foot is divided into tentacles • Most intelligent invertebrates

  16. http://www.youtube.com/watch?v=7ujRgSRYE9A • http://www.youtube.com/watch?v=1rDsK9qxxAk&feature=related

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