Sondra A. White
Objectives
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1. Students will be able to identify a univalve and a bivalve.
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2. Students will be able to successfully draw a three-dimensional shell on a flat surface.
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3. Student will be able to identify and measure shells found in the area. (Shells are made of CaCO3 and may dissolve or change over time if not cared for properly. See Nancy Wyskiel’s unit).
Motivation
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Most students enjoy going to the beach and at one time or another they have experienced picking up pretty shells along the way. Shells often show many colors; red, orange, green and blue. Some shells may have pearly luster colors or some may have very little color, perhaps black with a little variation of white. We are going to study shells. We will be able to give their names and be able to identify them.
Show an example of a large pink counch, moon snail and other mollusks. (black mussel, white and grey oyster) Discuss the texture of the shells—roughness or smoothness of the shell.
Procedure—
(This unit will be written in four parts.)
A.
Shells are Skeletons Too: Basic Background
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1. Shells are
invertebrates
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a. Invertebrates are animals without (an internal) backbone.
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b. Invertebrates build an exo-skeleton shell of CaCO3.
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c. An invertebrate shell is made up of calcium carbonate, Ca CO3.
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d. The shell material is built up by the animal and forms an exoskeleton.
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e. As the animal grows—the shell is enlarged by forming layers.of shell. There is a layer, called the mantle, which is a layer of skin covering the mollusk’s body. It is the interior part of the body of the animal. It secretes the shell or produces the minerals to make the shell layers.
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f. Shells vary depending on the amount of Ca CO3 per unit area. Some shells are thick (alot of Ca CO3) and are heavy. Others are paper thin and very light. (Show some examples)
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g. The animal (inside a bivalve shell) is called a
Mollusk
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(1) The name is a latin word (Mollis) which means soft.
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(2) The animal is soft-bodied although the shell is hard.
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(3) Two examples are clams and oysters.
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(4) The animals build their shells just as we unconsciously build our own skeletons.
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(5) Without these shells the animal cannot live.
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2.
Univalves—
Are animals that live inside one shell. Snails (land dwelling mollusks) and periwinkles (ocean dwelling mollusks) are classified as univalves.
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3.
Bivalves—
Are animals that have two shells, hinged together (clams, oyster). The muscle keeps the shell closed. Refer to Vocabulary Handout #3.
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4.
Shell Growth—
As the shelled animal gets older they grow a bigger shell. There may be ridges on the shell showing growth increments of the annual cycle. Once the animal’s mantle stops building it’s shell, the animal inside cannot grow any larger.
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5.
Reproduction
—(Refer to Shells Are Skeletons, Joan Berg Victor)
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a. Most mollusks hatch from very tiny eggs.
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b. Oysters produce millions of eggs—only a few survive.
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c. Snails hatch eggs in a protective capsule.
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d. Most snails and bivalve eggs develop into a minute organisms called Larvae. They swim around until they land on a hard object. Then they begin to develop and grow their shell. Some snails hatch into minute snails.
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6. There are six classes of Mollusks:
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a. bivalves: clams, mussels
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b. gastropods: (univalves) limpets, snails, slugs.
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c. scaphopods: the elephant tusk shells
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d. chitons: the roll up snail
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e. cephalopods: octopuses, cuttlefish and squid
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f. segmented mollusks: monoplacophora or gastroverms
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7. We will be drawing shells classified as gastropods (univalves) and bivalves.
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8.
Measuring A Shell
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Bivalve
(figure available in print form)
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Univalve
(figure available in print form)
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9. Test—handout #2 (Shells) Have each student tested on their basic background knowledge learned in this lesson.
B. Project #1—
A Univalve (Gastropod)
—Pencil Sketch with Pen and water soluable ink
Materials—
pencils, eraser, 12 x 18 newsprint, white drawing paper, pens, water soluable ink.
Motivation
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Show sample cards of drawings done of shell. Place them around the room on bulletin boards. Bring in samples of univalves that the students will be drawing. Go over the shade and line forms of the shell—Identify.
Procedure
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1. Pass out pencil, eraser and one piece of newsprint paper to each student.
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2. demonstrate in class how to begin drawing the shell. i.e.
moon shell
. . . described as a broadly round shell.
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Fig. A
(figure available in print form)
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Fig. B
(figure available in print form)
(figure available in print form)
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The basic form should be a broad circle—loosely sketched (Fig. A). Working from right to left put in the shell spiral lines (Fig. B). Next put in the curving lines (growth lines) that follow the spiral shape of the shell, Then the detail will follow . . . curving lines will give shape and form the three-dimensional drawing.
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3. Have the students pick out the univalve they wish to draw. Shells should be drawn at least two sizes larger.
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4. Each student should practice drawing the shell on newsprint paper until they feel ready to place their finished drawing on white drawing paper.
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5. Once the drawing is transferred on white paper, black ink may give color to their drawing. This may be used to show texture.
C. Project #2—
A Bivalve—
Pencil Sketch with watercolors and pen and water soluable ink.
Materials
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watercolors, brushes, water tins, pencil, eraser, newsprint, watercolor paper, pen, water soluable ink.
Motivation
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Do a quick sketch of a shell on watercolor paper.
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Explain the procedure of using watercolors:
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1. The more water applied to the brush, the lighter the color.
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2. The lesser amount of water on the brush will give a fine line and also a darker color.
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3. Once the pencil drawing is on the paper, you may dry-brush the watercolors by applying just the paint to a dry piece of paper.
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4, You may choose to wet the entire paper with clear water and then apply the watercolors. This gives a looser, washy look to the painting.
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5. After the paper drys, the students can outline the shell with pen and Black ink.
Procedure
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1. Hand out newsprint paper, pencil and eraser.
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2. Have the students pick out the Bivalve they wish to draw.
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3. They should begin to sketch their shell on paper. Sketches can be made of the shell in many positions.
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4. Once the student has chosen his sketch for his final drawing, he may transfer the drawing to the watercolor paper.
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5. Take a brush, watercolor tin, water tin and begin to apply color to the shell. Color can be set around the shell to represent the natural surroundings or applied directly to the shell.
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6. Allow the painting to dry.
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7. Get a pen and black ink. At random, outline sections of the pencil sketched shell.
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8, Frame the finished painting and display. Have the class have a critique on the finished paintings.
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9. Time allotted: one week.
D. Project #3—
Sea Shell Still Life—
Combined media
Motivation
—Arrange a still life of univalves and bivalves.
Talk about placement of shells: make sure they form an interesting arrangement. Some may be drawn as an overlapping design that uses only one shell, but repeats the shell to create an interesting pattern. Demonstrate in class.
Procedure
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1. Handout newsprint for sketching pattern of design.
2. Have students set up the still life they will be drawing.
3. Transfer sketch to white drawing paper.
4. Apply color by using any media they wish.
5. Have each student write a short paragraph explaining
6. Display all finished work on the bulletin boards.
(figure available in print form)
Vocabulary Handout #1: Anatomy
(figure available in print form)
Profile Head—Practice Sheet #1
(figure available in print form)
Profile Head—Practice Sheet #2
(figure available in print form)
Practice Sheet #3
(figure available in print form)
Practice Sheet #4
(figure available in print form)
Anatomical Hand Sketches—Practice Sheet #5
(figure available in print form)
Basic Proportions—Practice Sheet #6
(figure available in print form)
Vocabulary Handout #2: Anatomy
(figure available in print form)
Vocabulary Handout #3: Shells
(figure available in print form)
Test #2: Shells