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Chapter 15 Section 2 Mollusks and Annelid Worms Bellringer Unscramble the following words and write a sentence that uses all of the words. • gluss • isalns • sdusqi • klomssul Write your sentence in your science journal. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Objectives • Explain how mollusks eat, control body functions, and circulate blood. • Describe the four body parts that most mollusks have in common. • Describe the three kinds of annelid worms. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Mollusks •Most mollusks fit into three classes: • The gastropods include slugs and snails. • eat with radula, a toungelike organ covered in teeth • The bivalves include clams and other shellfish with two shells. • use gills to filter tiny plants, bacteria, and other particles from the water. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Mollusks, continued •The cephalopods include squids and octopuses. • grab food with tentacles and place it in their powerful jaws Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Mollusks, continued • Ganglia and Brains All mollusks have complex ganglia. •control breathing, movement, and digestion. • Cephalopods, such as octopuses, have large brains that connect all of their ganglia. • Most advanced nervous system of all invertebrates.. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Mollusks, continued • Pumping Blood • open circulatory system, a simple heart pumps blood through blood vessels that empty into sinuses, or spaces in the animal’s body. • Most mollusks have an open circulatory system. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Mollusks Pumping Blood , continued • closed circulatory system, a heart pumps blood through a network of blood vessels that form a closed loop. • Squids and octopuses Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Mollusks, continued • Mollusk Bodies • Foot – muscular foot for moving • Visceral Mass – gills, gut, and other organs are in visceral mass • Mantle – covers visceral mass and produces shell Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Annelid Worms • bodies have segments. A segment is almost an identical, repeating body part. • bilateral symmetry • closed circulatory system • complex nervous system with a brain. • Annelid worms live in salt water, fresh water, or on land. They eat plant material or animals. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Annelid Worms • 3 Major groups • Earthworms • Marine Worms • Leeches Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Annelid Worms, continued • Earthworms • Each earthworm has 100 to 175 segments. • Their castings, or waste, improves soil quality. • Tunnels allow air and water to enter soil • use stiff hairs, or bristles, on the sides of their bodies to move. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 15 Section 2 Mollusks and Annelid Worms Annelid Worms, continued • Marine Worms • Polychaete – many bristles • live in the ocean. • eat mollusks, other small animals, or filter food from the water. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Annelid Worms, continued • Leeches • Some leeches are parasites that suck other animals’ blood. • Other leeches eat dead animals or hunt insects, slugs, and snails. • Secrete a chemical to keep blood flowing and not form clots • Used for medical purposes • Doctors use leeches to prevent swelling. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.