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 2)flukes 3)tapeworms
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).

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

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

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

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

12. Classes
Oligochaeta
earthworm
Polychaeta
many bristled worms
Hirudinea
leeches

17. 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

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

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

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