To explore measurement.
 
Materials:

paper clips
links
white Cuisenaire blocks
inch/centimeter ruler
a drawing of a shell or an actual shell
spreadsheet application
computer with Internet access 
 
Procedures:

1.  Divide children into groups of two.

2.  Ask each group to measure the length of a shell with two units of measure.

3.  Ask groups to compare their results.  Did everyone record the same results?  Why or why not?

4.  Have each group measure the shell again using the white Cuisenaire blocks. Point out that each  block is a centimeter unit. Explain that the centimeter unit allows you to measure objects consistently, so that you can compare results.

Evaluation:

Each student will measure a series of five shells and record their results. Students can then create a graph of their data using a spreadsheet application. Students can compare and contrast graphs.

Extension Activity:

Create a display around the room or in the hallway to compare shell lengths.
Students can draw, cut to length, and color their home learning findings on butcher paper. 
Students can also visit  AltaVista   and click on "Image." Students can type in the name of shells or just 
the word sea shell to get online images of various shells.

Home Learning:

Research on the Internet to find the size of other shells.  
Examples: 
Giant Clam- four feet 
Tiger Cowry- three inches
Chitons- two and a half inches
Tulip- five inches

Record on paper and bring to class to share. In class, share data and have students create a 
spreadsheet and graph of shell sizes. Students can visit The Kids Graphing Page  to get tips on how to create charts and graphs.