phylum molluska
DESCRIPTION
Phylum Molluska. Characteristics of Mollusks. Aquatic (freshwater, marine) & Terrestrial External or internal shell or no shell Size: small (i.e. grain of sand) to large (20 meter squid) Bilateral Symmetry . Circulatory System of Mollusks. - PowerPoint PPT PresentationTRANSCRIPT
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Phylum Molluska
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Characteristics of Mollusks•Aquatic (freshwater, marine) & Terrestrial
•External or internal shell or no shell
•Size: small (i.e. grain of sand) to large (20 meter squid)
•Bilateral Symmetry
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Circulatory System of Mollusks•Open in most, blood not confined to
vessels (example: snails, slugs)
•Closed in others, blood is confined to vessels(example: squid, octopi)
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Larvae = trochophore•Free swimming
•Young form of animal
•Looks and behavesdifferently fromadult
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Body Plan of ALL Mollusks•FOOT - used for movement; contains
mouth
•VISCERAL MASS - internal organs
•SHELL – made of calcium carbonate; not all mollusks have
•MANTLE – a thin membrane that surrounds and secretes the shell
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Reproduction – mainly external fertilization
•Most are separate sexes▫Release sperm and eggs into the water
•Some are hermaphrodites▫Some water snails and some oysters
•Land mollusks have internal fertilizations ▫Male has a penis to transfer sperm
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Class Bivalvia“Bivalves”
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Bivalvia (Clam, oyster, scallop, mussel)•Have 2 VALVES (shells) held together by a
ligament held together
•Shell stays shut by adductor muscles
•They are FILTER FEEDERS▫Food and water enter the incurrent siphon; food
taken in by mouth▫Can accumulate toxins from the surrounding
environment
•GILLS for respiration
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Mussels attach to rocks with their BYSSUS THREADS (sessile)
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Scallops FLAP their shells to swim
•http://www.youtube.com/watch?v=_2iXHBuSIJY
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Clams burrow into sand/mud with their FOOT
•http://www.youtube.com/watch?v=HrBijKf0Ywk