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Name ______________________________________________________ Period _______ Score _________
Unit 5:
Molluscs
Unit Objectives
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Describe the structure and function of members of the phylum mollusca
Describe the ecological importance of members of the phylum mollusca
Give examples of members of the phyla mollusca
Explain the body plan of members of the phylum mollusca
Describe differences in the body plan of members of the phylum mollusca
Taxonomy
Kingdom Animalia
Phylum Mollusca
Mollusc: _________________________
General Characteristics
1. __________________________________________________________________________________
2. __________________________________________________________________________________
3. __________________________________________________________________________________
4. __________________________________________________________________________________
5. __________________________________________________________________________________
6. __________________________________________________________________________________
7. __________________________________________________________________________________
8. ___________________________________________________________________________________
Body Plan
Foot region: _________________________________________________________________________
Visceral Mass: ___________________________________________________________________________
Mantle Cavity: ___________________________________________________________________________
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Digestion: ________________________________________________________________________________
Radula: _____________________________________________________________________
Circulation: _______________________________________________________________________________
Nervous System: ___________________________________________________________________________
Respiration: ______________________________________________________________________________
Movement: _______________________________________________________________________________
Reproduction:
Sexual: _____________________________________________________________________________
Asexual: ____________________________________________________________________________
Ecological Importance
1. _______________________________________________________________________________
2. _______________________________________________________________________________
3. _______________________________________________________________________________
4. _______________________________________________________________________________
Classes
Class Polyplacophora: ______________________________________________________________________
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Examples: ___________________________________________
Class Gastropoda: _________________________________________________________________________
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Examples: ____________________________________________________________________
Class Bivalvia: ____________________________________________________________________________
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Examples: _________________________________________________________
Class Cephalopoda: ________________________________________________________________________
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Examples: _______________________________________________________
Chromatophores: ___________________________________________________________________________
Review
Example of a protozoan: _______________________ Example of a Porifera: ___________________________
Example of a cnidarian: _______________________ Example of a Platyhelminthes: _____________________
Example of a nematode: _______________________ Example of a mollusc: ___________________________
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Mollusc Reading/Coloring
The molluscs are members of the large and diverse phylum Mollusca, which includes a variety of
familiar animals well-known for their decorative shells or as seafood. These range from tiny snails, clams and
oysters to larger organisms such as squid, cuttlefish, chambered nautilus, and the octopus (the most intelligent
mollusc). The vast majority of molluscs live in marine environments, mainly near the shores. However, two
groups, the bivalves and the gastropods, can also inhabit freshwater and only the gastropod group contains
animals that live on land (snails and slugs).
Chitons are molluscs that live along ocean coastlines in most of the world, but some species have been
found in deep water. Chitons are the most ancient group of molluscs, their fossils date back 500 million years.
They creep along the shore slowly on their muscular foot and cling to rocks. Chitons have shells made up of 8
overlapping plates, in fact the name chiton means “bearer of many plates”. The plates are embedded in the
tough muscular band that surrounds the chiton's body. Label and color the band brown and the plates dark
green. This arrangement allows chitons to roll into a protective ball when threatened by predators and to cling
tightly to even irregular surfaces, like rocks and coral.
Chiton
Chambered Nautilus
Cephalopod Molluscs
The word cephalopod means “head foot”. The nautilus is a cephalopod, along with the octopus, squid
and cuttlefish. Cephalopods are characterized by having a large head area with a foot that has been adapted over
evolutionary time into tentacles. Cephalopods can have a few to as many as 100 tentacles. Cephalopods can
squirt an ink in defense to give them time to escape their predators and they can also camouflage themselves to
hide in the coral reef or on the sea floor. They have special color changing cells called chromatophores.
Chromatophores allow cuttlefish and octopi to change color almost instantly and blend into their surroundings.
The Chambered Nautilus is the best known species of nautilus. The spiral shaped shell, when cut
away, reveals a lining of shiny mother-of-pearl. The nautilus is another ancient species of mollusc. The fossil
record shows that the nautilus has not changed much over the last 200 million years of evolution. The nautilus
has primitive eyes compared to other cephalopods, mostly due to the fact that they have no lens. It has about 90
tentacles and NO suckers which is also different from other cephalopods. This nocturnal animal has a pair of
rhinophores, which detect chemicals that the animal uses smell to find its food. Color the shell sections of the
nautilus alternating pink and purple.
The word octopus means "eight feet." Octopi (plural form) are solitary animals with tentacles or arms
that have suckers. They live on the ocean floor. There are over 100 different species of octopus. The Giant
Octopus is the biggest octopus. This huge mollusc is up to 23 feet long from arm tip to arm tip, weighing up to
400 pounds. The smallest is the Californian octopus, which is only 3/8 inch long. An octopus has a soft body
and eight arms. The soft body is covered by a protective layer called the mantle. Label and color the head and
mantle blue. Each arm has two rows of suction cups. If it loses an arm, it will eventually regrow (regenerate)
another arm. Label and color the arms green and the suckers purple. It has blue blood. An octopus has an eye
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on each side of its head and has very good eyesight. Label and color the eye yellow. An octopus cannot hear.
Octopi eat small crabs and scallops, plus some snails, fish, turtles, crustaceans (like shrimp), and other octopi.
They catch prey with their arms and kill it by biting it with their tough beak. Color and label the beak red. They
can also paralyze the prey with a neurotoxic poison that softens the flesh. They then suck out the flesh. Octopi
hunt mostly at night. Only the Australian Blue-ringed octopus has a poison strong enough to kill a human.
Octopi live in dens, spaces under rocks, crevices on the sea floor, or holes they dig under large rocks. Octopi
pile rocks to block the front of their den. The den protects them from predators (like moray eels) and provides a
place to lay eggs and care for them. A mother octopus doesn't eat during the entire 1 to 2 months she is caring
for her eggs. In order to escape predators, an octopus can squirt black ink into the water, allowing the octopus
to escape. Another defense that octopi have is changing their skin color to blend into the background,
camouflaging them. The octopus swims by spewing water from its body through a siphon, a type of jet
propulsion. Label and color the siphon orange.
Read the definitions below and color and label the SQUID diagram using the information in the table.
Arms
Eight short limbs, each of which as 2 rows of suction cups on the lower side. The arms hold the
food while the squid bites it into swallowable pieces. (RED)
Beak and The parrot-like beak on the mouth is used for biting food into smaller pieces. The beak and mouth
Mouth are surrounded by the bases of the arms and tentacles. (cannot see it on diagram but ca label it
beneath the arms and tentacles)
Feeding
tentacles
The two long tentacles are used for obtaining prey, they have toothed suckers near the tip (BLUE)
Clubs
The ends of the feeding tentacles, which have toothed suckers (YELLOW)
Head
The small part of the body between the mantle and the arms. The head contains the eyes, the brain,
and the muscular buccal mass, which crushes the food (PINK)
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Mantle
Eye
Siphon
Fins
The large part of the squid in front of the head. Inside the mantle are the stomach, gills, ink sac,
reproductive and digestive organs (PURPLE)
An organ used to see. Squid have 2 very large eyes. (ORANGE)
A tube-like organ on the lower side of the head, it expels water forcefully allowing the squid to
propel itself through the sea (BROWN)
Two flaps on the mantle that are used to stabilize the squid during swimming (GREEN)
Gastropod Molluscs
The word gastropod means “stomach foot”. Snails and slugs have adapted their muscular foot on the
ventral side of their body and use it to “creep” along. Gastropods include snails and slugs and are the largest
group of molluscs, with more than 62,000 described species. In total, gastropods make up 80% of all animals in
the phylum Mollusca. Most gastropods live on land but some snails and slugs live fully submerged in water.
However, all gastropods need to keep their skin moist to survive. Most gastropods have a single, spiral coiled
shell to protect it from predators. Some snails have an operculum, a horny plate that seals the opening of the
shell when the snail’s body is inside. Carrying around the heavy shell means that snails cannot move very
quickly. Some species of gastropods have lost their shell completely, like slugs. Most gastropods have separate
sexes but some are hermaphroditic, although they do not fertilize their own eggs. Gastropod feeding habits
are extremely varied, although most make use of a radula in some aspect of their feeding. Some gastropods
graze, some browse, some feed on plankton, some are scavengers, eating decaying matter and some are active
predators.
Read the definitions below and color and label the SNAIL diagram using the information in the table.
Eyespots
Located at the tips of the long sensory tentacles on the snail (RED)
Respiratory Pore A small hole in the side of the body used for breathing (YELLOW)
Foot
Mouth
Shell
The soft, muscular part of the snail that allows the snail to move (GREEN)
On the underside of the head, it contains the radula, a file-like tongue that breaks down the
snail’s food
The hard, spiral, protective covering of the snail. (BROWN)
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The front part of the snail containing the tentacles, eyes and mouth (PINK)
Head
Tentacles
Two long and two short sensory tentacles on the upper surface of the snail’s head (ORANGE)
Bivalve Molluscs
Clams are animals that burrow under the sea floor. They are bivalves, molluscs that have two shells that
protect a soft body inside. The shells of a bivalve are made of calcium carbonate, the same material human
bone is made of. The oldest and highest part of the clam shell is called the umbo. Label the shell and the
umbo. The clam's shell is laid down in rings. The rings close to the umbo are the oldest and the rings that are
furthest from the umbo are the newest. Label and color the rings alternating red and brown. Label the oldest
and the newest rings. The biggest clam is the Giant Clam is up to 4.8 feet long and weighs up to 550 pounds.
Most clams are only a few inches long. Clams come in many colors, including shades of brown, red-brown,
yellow, cream, etc. The two shells are attached by a muscular hinge and open and close with the help of an
adductor muscle. Label and color the muscular hinge orange. When a clam is threatened, most clams will pull
their soft body into the shells and close the shells tightly for protection. The foot is used to burrow into the sand
and to move around. The foot can be extended outside the shells or valves. Color and label the foot blue.
Clams use their tube-like siphon to draw in water, from which they extract oxygen and filter plankton (tiny
plants that they eat.) Clams have both an incurrent (right) and excurrent siphon (left) for water to enter and
leave. Label and color the siphons yellow. Draw arrows in the direction that water is moving in/out of the
siphons.
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