Biology 27.4
Transcript of Biology 27.4
27-4 Mollusks
trochophore
• Free-swimming larval stage of an aquatic mollusk
foot
• Muscular part of a mollusk
mantle
• Thin layer of tissue that covers most of a mollusk’s body
Shell
• Structure in mollusks made by glands in the mantle that secrete calcium carbonate
Visceral mass
• Area beneath the mantle of a mollusk that contains the internal organs
radula
• Tongue- shaped structure used for feeding by snails and slugs
siphon
• Tubelike structure through which water enters and leaves a mollusk’s body
Open circular system
• System in which blood is not always contained within a network of blood vessels
Key Concept
• Mollusks are soft- bodied animals that usually have an internal or external shell.
Key Concept
• The body plan of most mollusks has four parts: foot, mantle, shell, and visceral mass
Key Concept
• Gastropods are shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side.
Key Concept
• Members of the class Bivalvia have two shells that are held together by one or two powerful muscles.
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.