27.4 Mollusks Notes
 Nevada State Science Content Standard: L.12.D.1 Students know
organisms can be classified based on evolutionary relationships. E/S
 Objective:
Describe the defining features of mollusks.
Describe form and function in mollusks.
Identify the characteristics of the 3 main classes of mollusks.
Describe ecology of mollusks.
 Key Vocabulary
Trochophore – free-swimming larval stage of an aquatic mollusk (p 701)
Foot – muscular part of a mollusk (p 702)
Mantle – thin layer of tissue that covers most of a mollusk’s body (p 702)
Shell – structure in mollusks made by glands in the mantle that secrete calcium carbonate (p
702)
Visceral mass – are beneath the mantle of a mollusk that contains the internal organs (p 702)
Radula – tongue-shaped structure used for feeding by snails and slugs (p 702)
Siphon – tubelike structure through which water enters and leaves a mollusk’s body (p 703)
Open circulatory system – system in which blood is not always contained within a network of
blood vessels (p 703)
What are the defining features of mollusks? (p 701)
What is the basic body plan of mollusks? (p 702)
How is a mollusk’s shell made? (p 702)
How do shell-less gastropods protect themselves? (p 705)
What are the characteristics of the 3 main classes of mollusks? (p 705 – 706)
Where is a cephalopod’s foot located? (p 706)
Why are land snails restricted to moist environments? (p 703)
Describe how a cephalopod responds to external stimuli and explain how a
cephalopod’s nervous system is more complex than that of other mollusks. (p
707)