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Name: Date:
Phylum Mollusca
Kingdom: Domain:
*Text pages 677-680. This is required reading.
Examine the animal phylogeny below to understand the position of Molluscs in the animal kingdom. You
will observe a large diversity of molluscs at the Aquarium.
What does the term Mollusca mean? __________________________
Examples:
_____________________________________________________________________________________
Are they Protostomes or Deuterostomes?
Biology 11: Phylum Mollusca Page 1
Body Plan
The different body shapes of molluscs are variations on a single body plan as shown below.
-Study the diagram and state the functions of the three major distinguishing features of mollusks
1. Muscular Foot: _______________________________________________________________
______________________________________________________________________________
2. Visceral Mass: ________________________________________________________________
______________________________________________________________________________
3. Mantle: _____________________________________________________________________
______________________________________________________________________________
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Do most Molluscs have a shell? Where is it created and what is its function?
______________________________________________________________________________
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Biology 11: Phylum Mollusca Page 2
-Molluscs are divided into four classes
that all have their unique modifications
on the basic body plan:
1. Class Polyplacophora: Chitons
http://www.oceanlink.info/biodiversity/gumboot/gumboot.html
These sluggish animals feed on algae growing on rocky seashores.
Fossilized chitons have been dated up to 400 million years old.
2. Class Gastropoda: Slugs, Snails, Limpets, Abalone, etc
-Use your text to provide at least 3 interesting (not boring) facts
about gastropods.
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Biology 11: Phylum Mollusca Page 3
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3. Class Bivalvia: Mussels, Clams, Scallops, Oysters
Why is this group of molluscs called bivalves?
____________________________________________________
*Complete the sentence below using the following words: Oxygen, Cilia, Plankton, Water
Bivalves are generally stationary when feeding. They draw _______________in through a siphon, pass it
over their gills to extract ___________________and filter out ___________________ in a mucous layer.
The plankton is then moved to the mouth by the beating of ___________________on the gills.
4. Class Cephalopoda: Squid, Octopus, etc
This name means ________________________________________________________________
Biology 11: Phylum Mollusca Page 4
The molluscan body plan has been modified into various classes. In the diagram below the digestive tract
is shaded, the foot is stippled and the shell is marked by a heavy black line. Examine and compare the
different Molluscs very carefully.
Questions:
Biology 11: Phylum Mollusca Page 5
1. Which group of molluscs are filter feeders, getting their food by straining plankton from the water?
_____________________
2. Which group are active predators with excellent sensory structures and very fast locomotion?
_______________________
3. Which group are mainly herbivorous and get their food by grazing on plants or scraping algae?
________________________
4. Which group has 8 pieces of shell on the dorsal surface and clamps tightly to the rocks when
disturbed? _____________________
In preparation for the upcoming Cephalopod dissection, complete the table below comparing various
characteristics of a clam (Bivalve), squid (Cephalopod) and land snail (Terrestrial Gastropod)
Clam (Bivalve) Squid (Cephalopod) Land Snail (Terrestrial Gastropod)
Habitat
Feeding
Respiration
Circulatory system
Response
Movement
Biology 11: Phylum Mollusca Page 6
Cephalisation
Nervous System
Biology 11: Phylum Mollusca Page 7