Ch 27- Worm and Mollusks

1. Ch 27- Worm and Mollusks • Welcome to Discovery Education Player • Characteristics of flatworms • Soft, flattened worms with tissues and internal organ system • Simplest animals to have three embryonic germ layers • Bilateral symmetry • Cephalization • Acoelomates • Phylum Platyhelminthes • Coelom- fluid filled coelom forms between tissues of flatworms

2. No circulatory or respiratory systems • Pharynx- muscular tube that extends out for feeding • Flame cells- specialized cells that remove wastes from body • Ganglia- group of nerve cells that controls nervous system • Eyespot- group of cells that can detect changes in amount of light in their environment • Most are hermaphrodites that reproduce sexually • Hermaphrodite- individual with both male and female reproductive organs • Some reproduce asexually by fission- organism splits into 2 • Muscle cells and cilia to move

3. Groups of flatworms • Turbellarians- class Turbellaria • Free-living • Most live in marine or fresh water- bottom dwellers • Flukes- class Trematoda • Parasitic flatworms • Infect internal organs of host • No eye spots • Hermaphrodites • Burrow into intestines and release embryos into intestine- passed out with feces

5. Tapeworms- class Cestoda • Long, flat, parasitic worms • Adapted to life inside of intestines of host • Scolex enables worm to hook to host • Proglottids- segments that make up body • Contain both male and female reproductive organs • No eyespots • No mouth, grastrovascular cavity, or digestive organs • Hermaphrodites • Raw or undercooked food

6. Sec 2- Roundworms • Phylum Nematoda • Unsegmented worms • Bilateral • Long slender bodies • Cuticle • Most are free living • Have pseudocoeloms and digestive systems with 2 openings- mouth and anus • Pseudocoelom- false coelom, only partial with tissue dervived from mesoderm • Types include hookworms, trichinella, pinworms

7. Parasitic roundworms include trichinella, filarial, ascarid, and hookworms • Trichinosis- disease caused by trichinella, live in hosts intestines • Uncooked pork • Filarial worms- live in blood and lymph vessels of birds and mammals • Tropical regions of Asia, transmitted by biting mosquitos • Elephantiasis • Ascarid worms- live in host’s small intestine • Commonly spread by eating vegetables not washed properly • Can reach 50 cm • Hookworms- live in host’s intestines • Burrow into skin and enter bloodstream • Suck on host’s blood

8. Sec 3- Annelids • Phylum Annelida • Earthworms • True coelom lined with tissue derived from mesoderm • Closed circulatory system • Reproduce sexually, separate sexes and hermaphrodites • Long and narrow segmented bodies • Septa- internal walls that separates the body into segments • Setae- bristles that are attached to each segment • Nephridia- excretory organs that excrete nitrogen containing wastes • Clitellum- band of thickened, specialized segments that secretes mucous that contains eggs and sperm

9. Groups of Annelids • Oligochaetes- class Oligochaeta • Earthworms and relatives • Typically have streamline bodies • Relatively few setae compared to polychaetes • Most live in soil or freshwater • Leeches- class Hirudinea • External parasites that suck blood and body fluids of their host • Live in moist habitats in tropical countries • Polychaetes- class Polychaeta • Sandworms, bloodworms, and relatives • Marine annelids • Have paired, paddlelike appendages tipped with setae

10. Sec 4- Mollusks • Phylum Mollusca • One of oldest and most diverse phyla • Soft-bodied animals • Usually have internal or external shell • Include snails, slugs, clams, squids, and octopi • Trochophore- free-swimming larval stage • Characteristic of aquatic mollusks and annelids

11. Form and function in mollusks • Body plan of most mollusks • Foot, mantle, shell, visceral mass • Radula- flexible tongue shaped structure used for feeding by snails and slugs • Octopi use sharp jaws to eat prey • Clams, oysters, and scallops are filter feeders • Siphon- tubelike structure through which water enters and leaves the body • Open circulatory system

12. Groups of Mollusks • Gastropods- class Gastropoda • Pond snails, land slugs, sea butterflies, sea hares • Shell-less or single shelled mollusks • Move by using muscular foot located on ventral side • Bivalves- class Bivalvia • 2 shells that are held together by one or two powerful muscles • Clams, oysters, mussels, and scallops • Cephalopods- class Cephalopoda • Most active • Octopi, squids, cuttlefishes, nautiluses • Soft bodied mollusks in which head is attached to single foot • Foot is divided into tentacles or arms