CECmisc.51


TITLE:    CHARTING MOLD GROWTH

AUTHOR:   MELODIE HILL, LEWIS ARRIOLA ELEMEN., CORTEZ, CO

GRADE LEVEL/SUBJECT:   Appropriate for grades  2-6

OVERVIEW:  Micro-organisms live, grow and reproduce all
around us.  They are both detrimental and helpful.  This
activity is designed to show students that they are all
around, and that their population growth can be charted
based on food supply.

OBJECTIVE(s):  Students will be able to:
1.   Identify sources of micro-organisms (air, water, etc.)
2.   Show micro-organism growth on an available food supply.
3.   Chart micro-organism growth and decline as the food
     supply runs out.
4.   Describe factors that inhibit micro-organism growth
     (cold, sunshine, sterilization, etc.)
5.   Describe ways that micro-organisms are used
     successfully.

RESOURCES:Small container or jar, tape, bread, boiling water
to sterilize, access to refrigerator, graph paper, yogurt,
cheese, yeast bread slices, hand lenses.Student resources:
pencil or writing utensil.

ACTIVITIES:
1.   Using tape, label a container, (Jar, small petri-dish,
     etc.) with the students name.  Select some to sterilize
     with boiling water.  Select some to leave as is.
2.   Place half a piece of bread in each jar.  Seal with
     tape.  Label with variable being tested.  Place some
     outside in the sunshine,  place some in the
     refrigerator,  leave some as is.
3.   Cut Graph paper circles and tape on bottom of petri
     dish.  Count number of squares visible each day.
     Numbers should decrease.  Observe over several days
     with hand lens.  As food supply runs out, mold will
     begin to die off itself.  Number of visible squares
     will remain the same, or increase.  Have students keep
     a graph of several days growth.  Mark points of
     increase, stabilization and decrease.
4.   Compare class results.  Cultures grown in refrigeration
     and under sunlight will have little growth.  Cultures
     grown under sterilization will have little or no
     growth.  Those left as is will have  abundant growth.
5.   Bring bread dough, yeast, yogurt, etc.  Explain that
     micro-organism growth has productive side effects.
     Parent volunteers can help you make yeast bread, or
     yogurt with the class