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The central axis around which the shell of a snail coils is called the __________?
columella
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What is there about snails and other members of their class that makes them different from the other members of this phylum?
their bodies twist 180 degrees bringing the posterior most part of the body just behind the head.
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The newest clam shell is built where?
On the inside so the inside nacreous layer is the newest
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Clams burrow by using what?
foot
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The tongue-like, rasping organ in the head of many molluscs is the _____________.
radula
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Although snails and some other molluscs are hermaphroditic, most molluscs are either male or female, a condition called ________?
dioecious
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The cephalopod nervous system is best described as _____?
the most advanced among molluscs and with large acute eyes and well-developed neurons
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Because shells require it, land snails are limited to soils that contain some level of ______?
calcium
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The Monoplacophora have:
several internal organs that are serially repeated
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Which correctly describes the evolutionary origin and adaptive radiation of molluscs?
molluscs originated in the sea, bivalves and gastropods invaded brackish and freshwater environments, and just gastropods invaded the land.
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In some molluscs, the free-swimming larva is a trochophore while in others, it is a veliger with the beginnings of a foot, shell and mantle. What is the relationship of these molluscan juvenile stages?
The trochophore is considered ancestral and the veliger is a derived larval stage
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The water current in the body of a cephalopod mollusk provides
- oxygen for respiration
- carries wastes/gametes out of the body
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Of all of the freshwater organisms, more freshwater clams are becoming endangered than other species. What is the likely reason?
as filter-feeders, they concentrate pollutants and are more likely to be harmed by water pollution
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Cultured pearls are made by
placing an irritating particle under the shell mantle
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The main structures that taste food and direct it into the mouth of a clam is/are
labial palps
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Snails that lack gills are called "pulmonate" and their mantle cavity functions as what?
a lung
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Gaseous exchange in gastropods may involve
- gills
- lungs
- mantile
- body surface
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The Polyplacophora
live in the ocean, especially in intertidal areas
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The _________ is the oldest part of the shell and growth occurs in concentric rings around it.
umbo or apex
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The ______________ is the layer on the outside of the clam or mussel shell that provides protection from acidic water and may be colored to hide the clam in the mud.
periostracum
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