Ice Mummies
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Student Handout |
This is Rotten
When an organism dies, it begins to be broken down by lots of microorganisms like bacteria and mold. But what
happens to the organism at different temperatures? Do this experiment with your own samples and find out!
Procedure
On a separate sheet of paper, predict
what you think will happen to your food sample in each environment. Boil 1/2 cup of water. Remove from
heat. Add 2 teaspoons of gelatin
and 2 teaspoons of sugar. Stir until
dissolved. Let the solution cool for 10 minutes. Fill the bottom of each Petri dish about halfway. Put the lids on and let stand overnight. This is your
medium to support microbial growth. Collect your assigned food sample,
slice into thirds, and place one slice in each Petri dish. Tape, but don't seal, the Petri
dishes closed (see illustration). Label each dish with the contents and date.
 Place the dishes in a dark place,
such as a cupboard or drawer. Check the samples daily. Make a
chart and record daily progress of the microbial growth. Describe color, size, and fuzziness, as well as anything else you see. (Make sure to not touch the samples.) You may want to draw what you see as well. Once you have obtained a quantity
of microorganisms growing, record the temperature of the three locations (refrigerator, freezer, and cupboard or drawer) and place one sample in each. Check the samples every few days.
Record your observations in your chart. Make sure you don't open your Petri dish once something has started
to grow. After two weeks, make your final
observations and describe what
you see.
Questions
Write your answers on a separate sheet of paper.
Which sample showed the most microbial growth? Which showed the least? Why? Did the samples in each environment grow at the same rate or at different rates? Why? What else could you do with the samples to promote microbial growth? What could you do to limit growth? How might an archeological find, such as a body, be affected by the temperature of the environment in which it is found?
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