1. 27-4 Mollusks

2. trochophore
• Free-swimming larval stage of an aquatic
mollusk

3. foot
• Muscular part of a mollusk

4. mantle
• Thin layer of tissue that covers most of a
mollusk’s body

5. Shell
• Structure in mollusks made by glands in the
mantle that secrete calcium carbonate

6. Visceral mass
• Area beneath the mantle of a mollusk that
contains the internal organs

7. radula
• Tongue- shaped structure used for feeding by
snails and slugs

8. siphon
• Tubelike structure through which water enters
and leaves a mollusk’s body

9. Open circular system
• System in which blood is not always contained
within a network of blood vessels

10. Key Concept
• Mollusks are soft- bodied animals that usually
have an internal or external shell.

11. Key Concept
• The body plan of most mollusks has four
parts: foot, mantle, shell, and visceral mass

12. Key Concept
• Gastropods are shell-less or single-shelled
mollusks that move by using a muscular foot
located on the ventral side.

13. Key Concept
• Members of the class Bivalvia have two shells
that are held together by one or two powerful
muscles.

14. Key Concept
• Cephalopods are typically soft-bodied
mollusks in which the head is attached to a
single foot. The foot is divided into tentacles
or arms.