Questions and Answers
All members of the phylum Mollusca have radial symmetry.
False
A flexible tongue-like structure with abrasive teeth that point backward is called a chromatophore.
False
Mollusks are divided into classes based on the characteristics of their foot.
False
Nudibranchs are marine gastropods that lack a shell.
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Bivalves are the only molluscs that do not possess a foot.
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Bivalves lack a distinct head and there are no specialized sense organs.
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The fertilized egg of a clam develops into a pinnula larva.
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Most clams have separate sexes.
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Cephalopods have a complex brain and well-developed sense organs.
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What class do nudibranchs, snails, and slugs belong to?
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What class do squid, octopus, nautilus, and cuttlefish belong to?
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What class do chitons belong to?
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What class do tusk shells belong to?
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What class do clams, oysters, scallops, and mussels belong to?
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What class of mollusk is intelligent, with a well-developed nervous system?
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What class of mollusk has no distinctive head?
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What classes of mollusk have an open circulatory system?
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What class of mollusk has a closed circulatory system?
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What class of mollusk has external shells present in some species?
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What class of mollusk has all carnivorous species?
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What class of mollusk uses radula in feeding?
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What class of mollusk all use gills for both respiration and food collection?
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What class of mollusk bites prey with a beak?
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What class of mollusk has a shell that contains 8 overlapping plates on the dorsal surface?
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What class of mollusk has a pair of tentacles on their head?
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What class of mollusk uses excretory structures called nephridia?
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What class of mollusk are all marine species?
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What class of mollusk is known for their great camouflage abilities?
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What class of mollusk undergoes torsion?
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What class of mollusk swims by jet propulsion?
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What kind of shell does a squid have?
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Describe the foot of a cephalopod.
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What purpose does the foot of a cephalopod serve? How is the foot adapted for this purpose?
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What are some other animals in the cephalopod class?
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What class do snails belong to?
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What shell do gastropods have?
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Describe the foot of a gastropod.
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What is the foot of a gastropod used for and how is it adapted for this?
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What are some other animals in the gastropod class?
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What class does a clam belong to?
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Describe the shell of bivalves.
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Describe the foot of a bivalve. What purpose does it serve? How is this foot adapted for its purpose?
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What are some of the other animals in Bivalvia?
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Free swimming ciliated larva found in molluscs.
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Body symmetry in which the right and left sides mirror one another.
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Layer of soft tissue that covers the visceral mass.
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Structure made of calcium carbonate that protects the soft bodies of some mollusks.
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Structures found in aquatic molluscs that are specialized for gas exchange.
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The process occurs during gastropod larval development and results in the 180-degree twisting of the visceral mass.
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Feeding strategy used by bivalves.
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Color-changing pigment cells that provide camouflage to cephalopods.
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What is the only cephalopod to retain its external shell?
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What class contains snails, slugs, and nudibranchs?
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Members of this class have a body plan consisting of a head, foot, and visceral mass.
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The members of this class are free swimming predators.
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Members of this class have a radula.
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This class has the most advanced nervous system.
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Members of this class have a trochophore larva.
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This class contains animals whose foot is divided into arms and tentacles.
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Members of this class undergo torsion.
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Members of this class have bilateral symmetry.
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Members of this class have most species having only one shell but some have none.
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All species in this class have two shells.
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Members of this class are filter feeders.
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Animals in this class have a closed circulatory system.
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Members of this class have an open circulatory system.
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Most members of this class have no shell.
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This muscular structure is used for burrowing into the sand.
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These powerful muscles are used to open and close the valves.
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The opening into the digestive system.
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This structure connects the two valves.
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Thin layer of epidermal tissue that covers the visceral mass.
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These structures help direct food into the mouth.
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Name given to sex organs.
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Area where digested food is absorbed into the blood.
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Structure through which water, food, and oxygen enter the clam.
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Site of digestion.
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Shells are known by this name.
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This pumps blood through the open circulatory system.
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Opening leading out of the digestive system.
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Structures that are responsible for absorbing oxygen from the water.
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Structure through which water and wastes leave the clam.
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Secretes enzymes responsible for the speedy digestion of food.
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Made of calcium carbonate and provides protection to the clam.
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Label the structure.
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Label the structures.
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What is the composition of a mollusc shell? What are the different layers of a mollusc shell? How is the shell made? What structure(s) help to make the shell?
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Describe the difference in feeding methods among gastropods, cephalopods, and bivalves.
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Relate the type of movement with the structure of the foot in the snail, clam, and squid.
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What adaptations allow cephalopods to be excellent predators?
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In what ways are cephalopods more advanced than the other classes of molluscs?
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What roles do molluscs play in the ecosystem? State three examples.
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List and describe the three main parts of the molluscan body plan.
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How and why do cephalopods change color?
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List three or more ways the nautilus is different from other cephalopods.
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What is the outer layer of the shell?
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What is the second layer of the shell?
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What is the innermost layer of the shell?
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Study Notes
Phylum Mollusca Overview
- Members exhibit bilateral symmetry, not radial symmetry.
- Distinctive structures include the radula (a tongue-like organ for feeding) and the mantle (tissue covering the visceral mass).
Classes of Mollusca
- Gastropoda: Includes slugs, snails, and nudibranchs; exhibit torsion during larval development; utilize a radula for feeding.
- Cephalopoda: Includes squids, octopuses, and cuttlefish; possess a closed circulatory system; highly developed nervous system; capable of jet propulsion.
- Bivalvia: Comprises clams, oysters, and mussels; have shells divided into two halves; use gills for filter feeding.
- Polyplacophora: Chitons characterized by eight overlapping plates on the back.
- Scaphopoda: Known as tusk shells.
Anatomical Features
- Foot: Serves various purposes—burrowing in bivalves, movement in gastropods, and modified into arms in cephalopods.
-
Shell Structure: Composed of three layers:
- Periostracum: Outer protein layer protecting from erosion.
- Prismatic Layer: Main structure made of calcium carbonate.
- Nacreous Layer: Inner layer known as mother of pearl.
Feeding and Respiration
-
Feeding Strategies:
- Gastropods utilize radula to scrape surfaces for algae; some are scavengers.
- Bivalves filter feed using gills for both respiration and food collection.
- Cephalopods are carnivorous, using tentacles and beaks for capturing prey.
Reproductive Features
- Most clams have separate sexes; fertilization involves development through trocophore larvae.
- All mollusks possess gonads, responsible for reproduction.
Ecological Roles
- Mollusks play vital roles in ecosystems as food sources for various organisms, including birds and mammals; contribute to nutrient recycling and soil regeneration.
Adaptations
- Cephalopods exhibit advanced adaptations, including chromatophores for color changes, enhancing their ability to camouflage and communicate.
Movement
- Squids utilize jet propulsion for swift movement, snails crawl using muscular contractions, and clams burrow into the substrate with their foot.
Unique Class Characteristics
- Cephalopoda: Characterized by intelligence and complex behavior; possess varied tentacle structures adapted for predation.
- Gastropoda: Display a wide range of forms and can be found in marine, freshwater, and terrestrial environments; most species feature a spiral shell.
Special Features
- Nautilus has a distinctive coiled shell; differs from other cephalopods by having a chambered structure and nocturnal behavior.
- Advanced nervous systems in cephalopods facilitate learning and memory, distinguishing them from other mollusks.
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Description
Test your knowledge of the phylum Mollusca with these flashcards. Each card presents a statement regarding mollusks, where you'll determine its accuracy. Perfect for students and enthusiasts looking to deepen their understanding of these fascinating creatures.