Mississippi Science ZOO.3.5
The Standard
- ZOO.3
- Students will understand the structure and function of phylum Mollusca, and how they adapt to their environments.
Develop a dichotomous key to contrast characteristics of gastropods, bivalves, and cephalopods.
2026 Mississippi College- and Career-Readiness Standards for Science · Phylum Mollusca
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students compare the body features of snails, clams, and squid. They write paired choices that lead a reader to gastropods, bivalves, or cephalopods, then test the key with more animals.
What Mastery Looks Like
- Their key sends a clam to bivalves by its two hinged shell halves. It sends a slug to gastropods by its crawling foot and a nautilus to cephalopods by its arms. Students can spot and fix a wrong route.
Common Misconceptions
- Students may sort by shells alone, which puts shell-less slugs and shelled nautiluses in the wrong groups. They may write choices like “lives in water” that fit more than one group.
How to Assess It
- Show pictures of a clam, slug, squid, and nautilus. Ask students to write a two-choice key for the three groups and trace the nautilus through it.
Lesson moves
Ways to Teach It
Give pairs a hinged clam shell, a snail shell, and photos of a slug, squid, and nautilus to build and test a key.
Write two sentences explaining why a shelled nautilus groups with squid, not snails, using its arms as evidence.
Swap keys with a partner, test each against slug and nautilus pictures, and revise any choice that fails.
Show photos of whole clams and squid from a seafood market, then use the key to label each and cite the visible clues.
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Printable ZOO.3.5 Worksheet
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Related Standards
- MAQ.7.3
Utilize a dichotomous key to identify select aquatic vertebrates.
- ZOO.1.1
Develop and use dichotomous keys to distinguish animals from protists, plants, and fungi.
- ZOO.3.7
Create a model comparing the anatomy of gastropods, bivalves, and cephalopods.
- MAQ.6.3
Develop a dichotomous classification key to be used in the identification of sample aquatic invertebrates.
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