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Kids' Inquiry of Diverse Species

Local animals in this group:

snails, clams, squids and octopodes

Mollusca

Mollusks are a large group of invertebrate animals. Mollusks have soft bodies, and their bodies are not divided into rings like the segmented worms called annelids . Mollusks don't have legs, though some have flexible tentacles for sensing their environment or grabbing things. Most mollusk species grow a hard shell for protection, but their shell grows in only one or two pieces. It doesn't have joints like the exoskeletons of insects and crustaceans .

There are almost 100,000 species of mollusks around the world, and many tens of thousands more undiscovered. Most mollusk species only live in the ocean, but some live in freshwater or on land. In Michigan there are about 300 species of mollusks known, with more to be found.

There are three main groups of mollusks. Snails ( Gastropoda ) are the most diverse group, there are tens of thousands of species. Nearly all snails grow a spiral shell that is all one piece. A few snail groups have stopped growing shells; they're called slugs . The next largest group is Bivalvia , the clams, oysters, and mussels . These are mollusks with two shells that they can close up tight for protection. Finally there is Cephalopoda , the squids and octopuses. They only live in salt water, so we won't say much about them here. They have no shells, but are larger, smarter, and faster than their relatives in the other groups. Squids and octopuses are all predators; they eat fish, crustaceans, and other mollusks.

 
University of Michigan Museum of ZoologyNational Science Foundation

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. "Mollusca" (On-line), Animal Diversity Web. Accessed August 21, 2017 at http://www.biokids.umich.edu/accounts/Mollusca/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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