Shells: Shell Sensations


BACKGROUND

Shells are a familiar sight along the beach, having been moved from the sea to the sand by the waves. Some beaches are famous for the numbers of shells which may be found there. And the variety of shapes and colors is amazing. Shells are the hard, external (in most cases) covering of certain invertebrates (animals without backbones) living in the ocean or in fresh water. This "exoskeleton" serves as protection for the animal's soft body. By the time the shell has washed up on shore, the former inhabitant has died and been removed from the shell. The majority, though not all, familiar shells are one of two types: "bivalves" and gastropods. Both are members of Mollusca, a division of the animal kingdom. The "bivalves" may be found singly or with the two parts still attached together. Clams and scallops are familiar examples. Gastropods include the familiar snails and slugs. Shells from gastropods vary from rounded (similar to the common garden snail) to narrow and pointed. Shells may be found with a variety of colors and patterns -- from pure white to dark brown and black, some with shadings of yellow, pink, or lavender. The beautiful, marbled iridescence of abalone shells, "mother of pearl", is exceptional. Shells have been used by humans for everything from tools to jewelry. Even animals have used shells for their own purposes. A case in point is the hermit crab which adopts an abandoned seashell for its protective "home". When it outgrows one shell, it searches for a new one that is "a better fit"!

INVESTIGATION   

PLACE TO BEGIN:  
How many different kinds of shells can you find? How are the different kinds the same and how are they different from one another? Are there variations among members of a single group of shells? What sense other than sight can be used to group the shells? 

MATERIALS:
Collection of shells of several different kinds (gathered from the beach or available online and in craft stores)

DIRECTIONS:
Place all of the shells together in a pile. With eyes closed, divide the group into two piles based on a single factor such as shape or texture. Then, with eyes open, group the shells according to kind based on appearance. Describe the characteristics of each kind or "population" of shells (e.g. size, shape, color, patterns, texture etc. Look for variations within each "population" of shells (for example, differences in patterns or color, differences in number of ribs etc.) Which shell is a favorite and why?

GOING FURTHER:
Are there differences in weight and size of the different kinds of shells?  [Remember to weigh/measure many shells and determine the average.]
How does the diversity of shells found in one location compare to that found in another?  [Graph the number of each kind for each location.]
Can you identify the names of the shells in your collection and make a dichotomous key?
(To learn more about how to use a dichotomous key and to see some examples, check out this link:
http://www.sci.sdsu.edu/SDSUTrees/)
If given a choice, what kind of shell does a hermit crab choose for its home?

DEVOTIONAL   

Read Revelation 7:9-12. What a wondrous thing God's people will experience when people of every nation and language will stand before the throne of God and worship the Lamb! When we look around our world today, we see great variety. God's creation is amazing in its diversity and uniqueness. Shells exhibit differences in shape, size, and color. Similarly, people are diverse in many ways. No two individuals are completely alike. Even twins have unique personalities. Yet all who love God and have accepted His gift of salvation will one day join together in worship and praise.

APPLICATION QUESTIONS:
1. Who do you know that loves the Lord but is very different from you in either physical appearance or personality?
2. How can you show love to someone who you may not like because they are different from you?
3. What do you think it will be like when every child of God is standing before Him in worship? What song would you like to sing to the Lord?

CREATIVE ACTIVITY

Make a decorative seashell box. Find a box with a good, sturdy lid. The size of box is dependent upon how many shells you have available. Cover the lid top with glue, spreading it rather thickly. Tacky glue works best. Place your shells artistically on the top, covering most of the area. Next, sprinkle sand so that portions not covered with shells are completely covered. Allow the glue to dry completely and then shake off any sand that has not adhered. Finally, repeat the process so that the sides of the box lid are covered. You may choose to use both shells and sand for the sides, or just sand. The entire box may be sprayed with a glaze if desired. This gives the shells a permanent wet look.



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