Phylum Mollusca

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Phylum Mollusca

• Biology I Honors

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Examples

• Class Gastropoda
• Snails, slugs
• Class Bivalvia
• Clams, oysters, scallops
• Class Cephalopoda
• Squid, octupus

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Habitat

• Fresh water
• Salt water
• Terrestrial

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Symmetry

• Bilateral

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Tissue Layers

• 3

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Support/Skeletal

• Exterior calcium carbonate shell
• More protection than support
• Reduced to small internal structure in cephalopods

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Muscular

• True muscles
• Foot
• Used for sliding in gastropods
• Used for burrowing in bivalves
• Used for swimming in cephalopods

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Digestion

• Complete
• Gastropods
• Carnivores
• marine
• Herbivores
• Radula scrapes plant material

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Digestion

• Bivalves
• Filter feeders
• Incurrent siphon takes water in
• Gills filter food
• Excurrent siphon gets rid of waste

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Digestion

• Cephalopods
• carnivores

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Respiration

• Gastropods
• lung

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Respiration

• Bivalves
• Gills
• Also filter food

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Excretion

• Kidney

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Circulation

• Open
• Blood and heart but no blood vessels

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Nervous

• Brain
• Especially well developed in octopus
• Less well developed in bivalves (ganglia)
• Ventral nerve cord
• Complex sensory organs
• Eyes especially good in octopus
• antennae

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Temperature

• Ectothermic

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Reproduction

• Sexual