Mollusks and segmented worms

1. Mollusks and segmented worms Chapter 6, Section 3

2. Mollusks • Soft-bodied invertebrates that usually have a shell (ex. Snails, mussles, octopus) • Have mantle and large muscular foot • Mantle: thin layer of tissue that covers the mollusk’s soft body • Water-dwelling mollusks have gills • Gills: organs in which carbon dioxide from the animal is exchanged for oxygen in the water • Land-dwelling mollusks have lungs • Lungs: carbon dioxide from the animal is exchanged for oxygen in the air

3. Mollusks- body systems • Have digestive systems with two openings • Have scratchy, tonguelike organ called radula • Radula: has rows of fine, teethlike projections used to scrape off small bits of food • Have open circulatory system • Do not have vessels to contain blood • Blood washes over organs

4. Types of mollusks • Gastropods • Largest group of mollusks • Have one shell • Live in water or on land • Move about on a large, muscular foot • Secretion of mucus allows them to glide

5. Types of mollusks • Bivalves • Has two shells joined by a hinge • Large, powerful muscles open & close shell • Gills filter water for food

6. Types of mollusks • Cephalopods • Most complex type • Have internal plate instead of shell • Closed circulatory system • Adapted for quick movement in ocean • Have mantle surrounding internal organs

7. Segmented worms • Annelids (earthworms, leeches, marine worms)- body made of repeating segments or rings that make worm flexible • Each segment has nerve cells, blood vessels, part of digestive system, coelom • Internal body cavity, separates internal organs from body wall • Closed circulatory system • Complete digestive system with two body openings

8. Exit ticket • What are the characteristics of annelids?