1. For each pair of terms, explain how the meanings of the terms differ.

a. crop and gizzard b. gastropod and cephalopod c. setae and parapodia d. clitellum and seminal receptacle e. incurrent siphon and excurrent siphon

2. Explain the relationship between hemolymph and hemocoel.

3. Choose the term that does not belong in the following group, and explain why it does not belong: incurrent siphon, excurrent siphon, trochophore, and crop.

4. Word Roots and Origins The word chitin is derived from the Greek chiton, meaning "tunic." Using this information, explain why the term chitin is a good name to describe this compound.

Understanding Key Concepts

5. Identify the functions performed by the cilia on a free-swimming trochophore.

6. List the main parts in the basic body plan of a mollusk.

7. Describe the main feeding adaptation of mollusks.

8. Identify whether or not each of the following mollusks has a shell: nudibranch, clam, snail, and slug.

9. Compare the body structure of a cephalopod to that of a gastropod.

10. Distinguish between polychaetes and other annelids. Which characteristics set polychaetes apart?

11. Explain how segmentation aids movement in earthworms.

12. Summarize why earthworms require a moist environment to survive.

13. Describe the organization of an earthworm's nervous system.

14. Identify a typical environment in which one member of each of the three classes of annelids may be found.

15. Summarize the characteristics shared by mol-lusks and annelids.


CONCEPT MAPPING Use the following terms to create a concept map that shows the major characteristics of the phylum Annelida: annelids, segmented worms, coelomates, setae, parapodia, Oligochaeta, Polychaeta, Hirudinea, earthworm, bearded fireworm, and leech.

Critical Thinking

17. Applying Information If a grain of sand or other irritant gets inside the shell of a bivalve, the mantle coats the irritant with the material that lines the inner layer of the shell. Many layers of this material form a pearl. However, making a pearl consumes resources that an oyster could use for other purposes, such as strengthening its shell. Of what advantage is it to an oyster to make a pearl?

18. Inferring Relationships Clams reproduce by releasing sperm and eggs into the water. How might this process affect the reproductive success of these mollusks? Would you expect clams to release many sperm and eggs or only a few?

19. Making Comparisons Clams are aquatic, and earthworms are terrestrial. Nevertheless, the feeding methods of clams and earthworms are somewhat similar. Explain how they are similar.

20. Interpreting Graphics The graph below plots the movement of the anterior end of an earthworm over time. Was the anterior end moving or stationary during the periods represented by the horizontal sections of the graph? Which of the earthworm's sets of muscles were contracting during the periods represented by the horizontal sections? Explain.

Earthworm Movement

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