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Unit 8 Chapter 27 Mollusks and Segmented Worms. What is a Mollusk? Bilateraly symmetry, coelomates, and well-developed body systems Soft bodies covered.

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Presentation on theme: "Unit 8 Chapter 27 Mollusks and Segmented Worms. What is a Mollusk? Bilateraly symmetry, coelomates, and well-developed body systems Soft bodies covered."— Presentation transcript:

1 Unit 8 Chapter 27 Mollusks and Segmented Worms

2 What is a Mollusk? Bilateraly symmetry, coelomates, and well-developed body systems Soft bodies covered by a thin mantle, which may secrete a shell

3 What is a Mollusk? Mollusks have a foot, a ventral structure for locomotion Some have an open circulatory system, blood moves through vessels & into open spaces around body organs Others have a closed circulatory system, blood moves through the body enclosed entirely in blood vessels

4 What is a Mollusk? Gastropods include snails and slugs One shell, “belly- footed” Radula = scraping tongue-like structure Radula magnified 1000X

5 What is a Mollusk? Bivalves include clams, oysters & muscles Two shells, “hatchet-footed” Filter-feeders

6 What is a Mollusk? Cephalopods include octopus, squid, cuttlefish, & chambered nautilus Little or no shell, foot divided into tentacles with suckers Use ink and jet propulsion to escape from danger

7 What is a segmented worm? Phylum Annelida Bilaterally symmetrical, segmented coelomates, with two body openings

8 What is a segmented worm? Earthworms have complex body systems: Digestive system includes a crop & gizzard for grinding food taken from soil Closed circulatory system includes 5 pair of “hearts” Reproductive system includes both ovaries & testes

9 What is a segmented worm? Leeches are freshwater, external parasites Some microsurgeons use leeches after surgery to improve blood flow

10 What is a segmented worm? Marine worms include bristle worms, fan worms and tube worms (below) Most have structures for swimming or crawling on the bottom of the sea


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