This is the fourth Investigation of the LabLearner CELL Science and Art. In it, students continue the exploration of perspective and the illusion of depth in paintings. In addition, students will study symmetry and its use in art.

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1. Use the Recall Cognitive Tool to begin the Investigation by reviewing what students learned about perspective, point of view, and field of view in Investigations One, Two, and Three.

Ask students: What do we do when getting ready to learn something new? Students should realize that the Recall tool is appropriate.

Pose the following questions to prompt student recall about art and perspective:

1. Ask students: What do you think of when you hear the word “perspective?” Student answers may vary.

2. Ask students: Do you think the words proportion and proportional are related to perspective? If so, how? Give examples. Students should recall that as an object is seen from further and further away, it appears smaller and smaller. However, the object will not remain identifiable if the change in the length and width are not proportional. That is, the width and height change proportionately at different distances. For example, if a wooden box is 4 meters high and 2 meters wide, this 4 to 2 (or 2 to 1) proportion between them must say the same. In this case, the height needs to be twice as high as wide. If the box is represented by an artist very near the viewer in a painting (in the foreground), it might measure 12 cm by 6 cm on the canvas. If the same box was painted further away in perspective, it might be 6 cm tall and 3 cm wide. It could also be any other size so long as the proportion is kept the same at 2 to 1.

Note: Students may wish to think of proportions in this context as a ratio between numbers. Ratios are often represented as 2:1 (meaning 2 to 1). The original wooden box in this example (4 meters by 2 meters) has a height-to-width ratio of 2:1.

3. Ask students: Complete the following statement: The smaller the visual angle either outside or inside the eye, the ________ the image of an object on the retina. Students should answer: “the smaller the image of an object on the retina.”

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B. Continue the review by encouraging students to apply what they have learned thus far by modifying the drawing they created in Investigation Three.

1. Remind students that in this exercise, they used what they had learned about perspective to create a drawing that showed depth.

2. Explain that in this part of the PreLab, you would like them to apply what they learned from Investigation Three to their drawing. You would like them to imagine how their drawing would look from a different perspective.

3. Tell students to imagine that they are now standing at the far end of the road they drew and looking back in the other direction.

4. Encourage students to create a new drawing from this different perspective.

5. When finished, students should be able to compare the drawings and see the same objects from two different perspectives.

6. Provide approximately 15 minutes for this activity.

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C. Continue the PreLab by explaining that in addition to perspective, one of the other key elements of art is its symmetry or lack of symmetry.

1. Introduce the word symmetry by reviewing its definition from the Scientist’s Glossary:

Symmetry: 

A type of pattern in which an object can be divided into equal divisions or parts. Symmetry can also refer to the idea of balanced proportions or the “beauty” that results from balanced proportions.

2. The painting on this slide is described as symmetrical because you can imagine drawing a line down its middle and having a balance of objects that are similar in size and color on each side.  When you look at the painting, you can imagine it as composed of two balanced parts with a dividing line at the apex of the arches.

This painting is entitled The Coronation of Mary. It was painted by the painter Bergognone around 1515. It was painted in the apse of san Simpliciano church in Milan, Italy. 

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This pattern is considered symmetrical because it can be thought of as a whole made up of repeating parts. The shapes in the inner circle repeat, and you can imagine drawing a line through the middle of the plate and seeing the mirror image on the other side of the line.

This dish is estimated to have been designed around 1525-1530 in Iznik, Turkey. The design in the center is probably based on a late 11th-century Islamic brickwork pattern. (The Metropolitan Museum of Art, New York)

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This large crustacean is considered to be symmetrical because its body is composed of right and left halves that are mirror images of each other.  You can imagine drawing a line down the center of this King Crab and dividing it into equal right and left halves.

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This slide shows examples of bilateral symmetry (the tiger, monarch butterfly, and ladybug) and radial symmetry (the snowflake and lemon half).

Discuss and understand the following terms:

Bilateral symmetry: 

One type of symmetry in which an imaginary line or plane divides an object into right and left halves.  Each half is a mirror image of the other.

Radial symmetry: 

A type of symmetry in which an object can be divided equally around a central axis or point by multiple lines or planes of symmetry.  A starfish is an example of an organism that has radial symmetry.  A pie cut into equal pieces is also an example of radial symmetry.

Plane of symmetry:

A line that divides an object into equal parts.  An object can have one or multiple planes of symmetry.

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D. Conclude the PreLab by allowing students to apply and rehearse what they have learned thus far.

1. Continue the discussion of symmetry focusing on three additional terms from the Student Data Record: radial symmetry, bilateral symmetry, and plane of symmetry. Students should be more familiar with these terms after having seen the Symmetry in Art and Science Presentation.

2. Provide students with an opportunity to explore two different types of symmetry by performing the following activity.  As students conduct this activity they should focus on the number and orientation of students rather than the gender, height or dress of students.

a. Divide students into groups of six.

b. Provide a meter stick, long piece of tape or other object that can be used to model a line.

c. Tell each group to place the meter stick on the floor.

d. Instruct two students to stand on one side of the meter stick and four students to stand on the other side of the meter stick (A).

e. Ask students: Is this pattern bilaterally symmetrical? Why? Students should indicate that the pattern is not bilaterally symmetrical because the meter stick does not divide the students into equal sections that are mirror images of each other.  Two students are on one side, and four are on the other side of the meter stick.

f. Next, instruct the students to orient themselves so that 1 student is on one side of the meter stick and five are on the other (B).

g. Ask students: Is this pattern bilaterally symmetrical? Why? Students should indicate that the pattern is not bilaterally symmetrical because the meter stick does not divide the students into equal sections that are mirror images of each other.  One student is on one side, and five are on the other side of the meter stick.

h. Instruct students to move so three students are on one side of the meter stick, and three are on the other (C).

i. Ask students: Is this pattern bilaterally symmetrical? Why? Students should indicate that the pattern is bilaterally symmetrical because the meter stick divides the students into equal sections that are mirror images of each other. Three students are on one side, and three on the other side of the meter stick.  Some students may suggest that the two parts are not mirror images of each other because the students on each side differ in appearance.  Remind students that at the beginning of the activity, they were asked to imagine that each student was the same in appearance.

One could ask, “which group is most bilaterally symmetric”? Now, all students will likely answer group C.

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j. Finally, direct students to form a circle around the meter stick. 

Tell students that they are now in a radially symmetrical pattern because there is more than one plane of symmetry for the circle.  Have students illustrate this by rotating the meter stick so that it “cuts” the circle in different places.  Each time, the meter stick divides the circle into mirror images.

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3. End the PreLab by explaining that students will investigate whether objects have bilateral or radial symmetry in the lab.

a. Tell students that in order to do this they will use a mirror to find a plane of symmetry.

b. Encourage students to consider the following question as they prepare for the lab: How many planes of symmetry does an object have?

Note: The Pentagon is radially symmetrical. Can you see where lines could be drawn to make several mirror images?