Lesson Overview:
This activity illustrates the process of mitosis, or cell division, in yeast. Cells carry on the many functions needed to sustain life. The most important of these functions is the ability to reproduce. Students will investigate the process of mitosis by observing yeast cells. They will compare the growth of yeast cells in warm vs. cold water, and will hypothesize as to which environment would be more conducive to cellular growth. Students will write their hypotheses and gather data in a science journal, which will also include drawings, graphs, and words. As an extension, students will explore scientific drawing as a means of communicating ideas and information, and discuss opportunities that exist in the field of scientific illustration.
Length of Lesson:
Two 45-minute periods
Notes:
This lesson is particularly suitable for students in grades 5-8.
Instructional Objectives:
Students will:
- grow yeast and observe the results through a microscope.
- describe through drawings and words what they observe in a science journal.
- conduct an experiment that compares the growth of yeast cells in warm and cold water.
- quantify the results of their experiment.
Instructional Plan:
Warm-Up
Begin this lesson with a warm-up activity related to scientific drawing. Discuss with students the fact that in science, drawing is used to communicate ideas and information. In order for others to interpret the information correctly, the picture must be highly detailed, accurate, appropriately scaled and colored, and clearly labeled. Scientific drawing requires that students create an accurate, true reflection of the phenomenon or object being observed.
Tell students that they will need to convey information through sketches and charts as part of an experiment they will be conducting on yeast cells. To practice, ask them to try sketching a part of their hand. If hand lenses or microscopes are available, distribute them to students or pairs of students. Ask students to look closely at one part of their hand (or their partner’s hand), such as the knuckle or fingernail. Have students sketch what they see, with as much detail and accuracy as possible. When finished, allow students to share and discuss their sketches, talking about techniques they used and any difficulties they encountered.
Preparing the Experiment
Discuss reproduction with students. Lead a discussion on the essential functions of living organisms, including reproduction. Compare the reproduction of yeast cells with the reproduction of humans. Discuss what is necessary for reproduction to be possible (i.e., taking in of nutrients, energy, etc).
Each workstation should be set up in advance with the following supplies (per group or pair): a package of dry yeast, two jelly jars, sugar, dry measuring cup, eye droppers, warm and cold water source, and a microscope (450X or better).
Break the class into small groups or pairs. Assign each to a workstation. Instruct each group to make a sugar solution for the yeast. Have the instructions on the board or on each table. You may also model the steps in front of the class. Fill the jelly jars with one cup of warm tap water, then dissolve 1 ½ tablespoons of sugar into the solution. Dissolve 1 teaspoon of yeast into the sugar solution. Stir gently.
Conducting the Lab Experiment
Have the students make slides of the solution. It is a good idea to model this procedure as you explain the steps. Using an eyedropper, place a few drops of the solution on a clean slide. Cover the drops with a cover slip and place the slides under a microscope. The students will need help focusing the microscope. Begin viewing under a low magnification and move to high. Once the yeast cells become visible, the students should describe with words and draw what they see in their science journals. The students should also count the number of cells they see and jot that number down in their journals.
Cover the jars. Have each group or pair label their jelly jars with their names and the word “cold” or “warm” using marker pens and masking tape. Store the “cold” solution in a refrigerator and the “warm “ solution in a warm place, such as an incubator or inside a stove set on low. The temperature in the warm place should be set between 98 and 100 degrees Fahrenheit. Let all of the solutions sit for 24-48 hours.
Have the groups write a hypothesis as to which jar of yeast will yield more buds—the yeast stored in the refrigerator or the yeast stored in the warm place. The students must state the reasons for their hypothesis.
After 24-48 hours, set up the students' tables with their labeled yeast solutions, slides, slide covers, microscopes and the students' science journals. Have each group examine the cold and warm samples under a microscope. Each pair or group of students will need a microscope, four slides and slide covers, the warm and cold yeast solutions, and their science journals.
Have students gather, tabulate, draw, analyze and compare their data. Instruct students to make charts that effectively relate their data and conclusions to their target audience. Allow students to share the results of their experiment with the class. Each chart should vary so the students can see a variety of ways to communicate similar information. Students’ charts should be posted and critiqued.
Assessment:
Have each group present the results of their experiment. The group’s presentation should incorporate the answers to the following questions:
- What was their original hypothesis?
- Was the hypothesis correct?
- How did the two samples compare?
The group’s charts should be clear and concise as well as aesthetically pleasing. The students should share their drawings from their science journals with the group. Encourage students to use their drawings in their charts.
Refer to the Mitosis Lab Experiment Assessment Rubric and the Assessment Rubric to further assess student work.
Extensions:
Discuss with students that there are many careers that bring together the arts and other disciplines. One field that brings together art and science is scientific illustration. This field requires that an artist possess not only strong artistic skills, but also, a high attention to detail, the ability to visualize and interpret information, and the ability to calculate and draw images to scale. Discuss some of the techniques required for accurate scientific illustration, as well as ways in which these drawings would be useful to scientists and to the public at large. For examples of scientific illustrations and the techniques employed to create them, go to the New York Public Library’s exhibit, Seeing is Believing: 700 Years of Scientific and Medical Illustration.
Discuss with students the role that scientific illustration has had in transmitting knowledge throughout history, as well as in recording changes in scientific understanding over time. Ask students to consider whether creativity plays a role in scientific illustration. Though the focus is on the accurate visual depiction of an object or phenomenon, is there any interpretation made by the artist? Is there any art that is truly objective, or is all art subjective to some extent?
Sources:
Print:
- Balkwill, F., and Rolph M. Balkwill. Cell Wars. London: Harper Collins, 1999.
- Berger, Melvin. Germs Make Me Sick. Revised ed. New York: Harper Collins, 1995.
- Brown, Robert J. 333 More Science Tricks and Experiments. Blue Ridge Summit, PA: Tab Books, 1984.
- Patent, Dorothy Hinshaw. Microscopic Animals and Plants. New York: Holiday House, 1974.
- Ruiz, Andre Llamas. The Life of a Cell. New York: Sterling publishing Co., Inc., 1996.
Authors:
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Susan Born-Ozment, Teacher
Oyster Bilingual Elementary
Washington, DC
