Because of their complex geometric shapes and aesthetically magnificent appearances, seashells are a subject of fascination for students of all ages. When teaching young science students about seashells, utilize activities that focus on the shell's role as a mollusk's living exoskeleton, and encourage students to pay close attention to the physical characteristics that make individual seashells unique.
Explain to the class that a mollusk's shell is its only bone, and have your students feel for their bones. Continue to explain that both seashells and human bones are made of similar substances: forms of calcium. Split the class into groups, and give each group a glass of white vinegar and a seashell. Have students pass around their shells so they can feel the hardness and bone-like texture. Then, have each group drop their shells into the vinegar. Call their attention to the bubbles that rise from the shells. Explain that the acidic vinegar is dissolving the calcium carbonate of the shell. The bubbles are carbon dioxide produced during the chemical reaction. Students can then discuss how more acidic ocean waters can hinder a mollusk's ability to grow a shell. At the end of class, let the kids feel how the shells have softened from the reaction.
Split the class into groups and give each group a pile of seashells. Tell the class that when you give the signal to begin, they should start sorting their shells according to whichever characteristics they choose. Afterward, have each group share the characteristics they used to categorize their shells. For example, one group might use size or color as the only discerning factor while another group might put nonhinged -- univalve -- shells with spirals in one group, nonhinged shells without spirals in another, and hinged -- bivalve -- shells in a third group. You can then lead a discussion about how observation is important in science and how observing physical characteristics tells you about where different shells come from and which types of mollusks produce them.
Sound of the Seashore
Bring a large conch shell into class and allow each student to hold the shell up to his or her ear to hear the "seashore" sound. Ask your students why they can hear sound in the shell, and if they think it actually makes sound. Then, take several cotton balls and stuff them into the shell. Pass the shell around again and let students listen. The sound will have disappeared. Explain that the sound they heard was just normal sound in the air, but that the hard, curving surface of the shell's interior caused the sound to bounce around and echo and sound similar to the noise of the seashore.
Pass out a seashell to each student, and explain learning about seashells is learning to be observant when examining them. Have students write one-page descriptions of their shells, and encourage them to be as specific as possible about what they see and feel. For example, have them indicate whether the shell appears complete or if it appears to be only half of a shell that hinges together with a second half. Invite students to document the textures of their shells and to count the number of spiral chambers -- if there are any. Afterward, have them present their shells and show how each shell is interesting and unique.
- Scientific American: How are seashells created? Or Any Other Shell, Such as a Snail's or a Turtle's?; Francis Horne
- University of California at San Diego - Birch Aquarium: Shell-Shocked
- Howard Hughes Medical Institute: Sorting Seashells
- Highlights: Why do You Hear Ocean Sounds in Seashells?
- Education World: A Seashell Lesson: Writing for Detail and the Scientific Process; Jayme Steighner
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