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Chapter 29

Chapter 29. Mollusks and Annelids. Section 1: Mollusks. Section 2: Annelids. Section 1. Mollusks. Objectives:. Summarize the evolutionary relationship between mollusks and annelids. Describe the key characteristics of mollusks.

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Chapter 29

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  1. Chapter 29 Mollusks and Annelids Section 1: Mollusks Section 2: Annelids

  2. Section 1 Mollusks Objectives: • Summarize the evolutionary relationship between mollusks and annelids. • Describe the key characteristics of mollusks. • Describe excretion, circulation, respiration, and reproduction in mollusks. • Compare the body plans and feeding adaptations of gastropods, bivalves, and cephalopods.

  3. Section 1 Mollusks A True Coelom • Coelom and Trochophore Mollusks and annelids have a true body cavity and many mollusks and annelids have a larval form called a trochophore.

  4. Section 1 Mollusks Key Characteristics of Mollusks • The mollusk body has three distinct parts: visceral mass, mantle, and foot.

  5. Section 1 Mollusks Key Characteristics (Con.)

  6. Section 1 Mollusks Key Characteristics (con.) • All mollusks except bivalves have a rasping tonguelike radula. Mollusks have well-developed organs.

  7. Section 1 Mollusks Key Characteristics (con.) • Organ Systems Most mollusks respire with gills but some respire with a primitive lung. Nephridia enable mollusks to recover the useful substances from their bodily wastes.

  8. Section 1 Mollusks Body Plans of Mollusks • Gastropods Gastropods (snails and slugs) live in oceans, in fresh water, and on land. Gastropods have an open circulatory system.

  9. Section 1 Mollusks Body Plans of Mollusks • Bivalves Bivalves (mussels, clams, oysters, and their kin) are aquatic and have hard shells called valves that protect their soft bodies. Bivalves have an open circulatory system.

  10. Section 1 Mollusks Body Plans of Mollusks • Cephalopods Cephalopods (octopuses, squids, and their kin) have a well-developed head region, many tentacles, and a closed circulatory system. Most cephalopods have no external shell.

  11. Section 1 Mollusks Zebra Mussels: Exotic Species

  12. Section 2 Annelids Objectives: • Identify the major change in body plan that distinguishes annelids from mollusks. • Describe the basic annelid body plan. • Describe the annelid digestive system. • Compare the three classes of annelids.

  13. Section 2 Annelids The First Segmented Animals • Annelids are coelomate worms that have segmented bodies and complex nervous systems.

  14. Section 2 Annelids Characteristics of Annelids • Annelids respire through their skin, and they have a closed circulatory system.

  15. Section 2 Annelids Hydrostatic Skeleton • The fluids within the coelom of each body segment creates a hydrostatic skeleton that supports the segment.

  16. Section 2 Annelids Classification of Annelids • Annelids are classified according to the presence or absence of setae and parapodia.

  17. Section 2 Annelids Annelid Groups • Marine Worms Marine polychaetes have parapodia and setae. Some are active predators and others are filter feeders.

  18. Section 2 Annelids Annelid Groups • Earthworms Earthworms burrow through the soil, ingesting it as they crawl.

  19. Section 2 Annelids Annelid Groups • Leeches Leeches lack parapodia and setae, and their segments are not separated internally. They may be aquatic or terrestrial, and some are parasites.

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