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. Trichinosis- disease caused by trichinella, live in hosts intestines
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 Soft-bodied animals
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