Theresa Figarelli, Jefferson Elementary, Everett, WA USING MICROSCOPES Appropriate for grades 3-6. OVERVIEW: This activity is used during a unit about cells. I use it to give the students the opportunity to see cells and to discover the difference between plant and animal cells. PURPOSE: To further the students understanding of cells and to give them the experience of using a microscope. OBJECTIVES: The students will be able to: 1. Describe the differences between plant and animal cells. 2. Operate a microscope. 3. Examine cheek cells, onion cells, and potato cells. ACTIVITIES: 1. How to Use a Microscope: The teacher will need to prepare a worksheet for the students showing a diagram of a microscope labeling all of its parts. The teacher will then provide the students with microscopes and guide them through an introduction to the following parts from top to bottom: Eyepiece 10x Body tube Revolving nose piece Objective lens 4x (low); 10x (medium); 40x (high) Stage Stage clips Carrying arm Mirror or light source (lamp) Base 2. Setting Up a Wet Mount Slide: The teacher explains that a wet mount slide gets its name because it is wet with either stain or water. Stains are used to color parts of cells so they may be seen easily. In order to view something with a microscope a person must be able to see through it. The object must let light through it - this means translucent. The teacher then demonstrates how to make a wet mount slide. Then the student will advance to prepare their own slides for observation. The teacher may draw the following diagram on the board and describe what she will do with the materials. A wet mount slide includes the following: a slide, a cover slip, a specimen, a drop of stain or water. When preparing a slide, hold the cover slip at an angle (as shown in the diagram above) and let it drop onto the slide slowly trapping the specimen between the two pieces of glass. A piece of onion skin is easy to use in this first activity. 3. Observing and Comparing Cells: Depending on the age of the students the teacher may choose to read the following directions to his/her students or share them on a worksheet: Onion Skin a. First take a piece of onion skin off the onion. b. Put it flat on a slide. c. Bring the slide to the leader for a drop of iodine stain. d. Carefully put on a cover slip remembering to angle it. e. Examine the cell under low then medium power. f. Ask the teacher to put it on high power. g. Draw a few cells showing what you observed in the space provided. h. Describe in a few sentences what you saw while looking at the cell through the microscope. Cheek Cells a. Using a toothpick scrape the inside of your mouth. b. Place it carefully on the center of the slide. c. Bring it to the leader for a drop of blue stain. d. Repeat steps d-h from onion skin directions. Potato Cells a. Using a knife carefully cut a very thin slice of potato. b. Have the leader add a drop of iodine stain. c. Repeat steps d-e from onion skin directions. d. Draw a few cells in the space provided. e. Describe what you saw. Now the teacher facilitates a discussion comparing and contrasting what the students observed. The following vocabulary should be discussed and or defined: Cell Walls Plants have thick cell walls to strengthen the plant stem. Cell Membranes Animals have thin membranes because they have other forms of skeletons. Chloroplasts Green colored structures that produce food. Nucleus Both plants and animals have these; they control heredity and cell division. Cytoplasm A clear liquid where most of the cells life functions occur. After the discussion the students should have the opportunity to observe the slides again so they may observe the items discussed. RESOURCES/MATERIALS NEEDED: Microscopes, slides, coverslips, potato, onion toothpicks, knife, iodine stain, blue stain, and worksheets. TYING IT ALL TOGETHER: This activity has been used in cooperative learning groups consisting of students of mixed ages grades 1-5. Also it has been used several times in fifth grade classrooms. The students enjoyed the experience and were able to learn the use of a microscope and depending on the age, gain a better understanding of cells. This is the best beginning microscope lesson I have found. It is especially useful for the fifth grade unit on cells. The students learn more about cells through actual observations than looking at textbook pictures.
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