Name Period

Chapter 18B Worksheet-

Mollusca/Annelida/Arthropoda

Reviewing Vocabulary

Write the word or phrase that best completes the statement. Use these choices:

closed circulatory system open circulatory system

mantle radula

nephridia

1. In bivalves, the is a thin membrane that sticks to both shells and forms siphons that are used for drawing in and expelling water.

2. The excretory structures that remove metabolic wastes from the bodies of animals such as mollusks and annelids are called .

3. You dissect an animal and observe pools of blood surrounding its internal organs. This animal has a(n) .

4. The is a tongue-like organ with rows of teeth that is used by gastropods to scrape, grate, or cut food.

5. An animal whose blood moves throughout it’s body within blood vessels has a(n)

.

Fill in the chart below comparing the different classes of mollusks.

Feature / Gastropoda / Bivalvia / Cephalopoda
External Shell / One (most species); none (slugs & nudibranchs
Head / No
Radula / Yes
Locomotion / Jet propulsion

Answer the following questions.

6. What adaptations help the octopus and the squid escape their predators?

7. What are some of the functions of the mantle in mollusks?

8. What is the role of the radula?

9. Compare the circulatory system of gastropods, bivalves, and cephalopods.

In the spaces at the left, write true if the statement is true. If the statement is false, change the italicized word or phrase to make it true.

10. In shelled mollusks, the radula secretes the shell.

11. Bivalves obtain food by predation.

12. The excretory structures in mollusks are called nephridia.

13. Gastropods have 2 shells.

14. The respiratory organs in aquatic gastropods are primitive lungs.

15. The first animals to have evolved respiratory organs are the mollusks.

16. The most complex and most recently evolved mollusks are gastropods.

Thinking Critically

Answer the following questions.

17. Most cephalopods lack an external shell. What is the adaptive advantage of this feature?

18. Compare the structures of a planarian and an earthworm with regard to the following: digestive tract, body cavity, and segmentation.

19. Suppose you are given an unknown mollusk to identify. The specimen does not have a shell. How could you decide whether the mollusk is an unshelled gastropod or a cephalopod?

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