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Web of Life    Mystery 3

Mystery 3 image

In this Mystery, students discover the role fungi play in decomposing dead materials and in creating soil. In the activity, students plan and conduct an investigation to discover the factors affecting decomposition.

Where do fallen leaves go?

Beginning Exploration (1 of 8)
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Beginning Exploration (2 of 8)

DISCUSS (1 of 2):

Where do you think all the leaves go?

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Beginning Exploration (3 of 8)

DISCUSS (2 of 2):

What could you do to find out?

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Beginning Exploration (4 of 8)
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Beginning Exploration (5 of 8)

DISCUSS:

What do you think is happening in the photo below?

Where do you think the stuff growing on the fruit comes from? rotting lemons

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Beginning Exploration (6 of 8)
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Beginning Exploration (7 of 8)

DISCUSS:

Imagine you were going camping for two weeks without a refrigerator and you wanted to bring some sliced oranges.

What might you do to keep the oranges from decomposing?

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Beginning Activity Prep
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Mold Terrarium

Step 1: Plan ahead.

In this activity, your group will make mold terrariums and observe mold growth for about two weeks. In addition to the supplies listed below, you will need a well-ventilated area to store your mold terrariums. The space you have available may limit how many terrariums you make.

Each mold terrarium will be sealed in a ziplock bag that is then sealed with packing tape. Your students will observe the mold through the clear plastic, but will not open the bags. When your observation period is over, you will throw the entire experiment away. Do not open the bag. Opening the bag would release mold spores, which can exacerbate asthma and cause respiratory illness.

Step 2: Get supplies.

For each mold terrarium, you will need the following supplies:

  • a sturdy paper or plastic plate like this that you can throw away when the experiment is done
  • a ziplock baggie that is large enough to hold the plate like these
  • half a slice of bread (Ask at a bakery or grocery store for day-old or expired bread.)
  • pieces of fruit (oranges and strawberries both mold well)
  • a strip of packing tape or duct tape for sealing the baggie
  • a label large enough for the team name, date, and starting conditions
  • a cup of water for moistening food

You will need to make a basic terrarium that contains damp food at room temperature. To observe the effect of different starting conditions, students will make mold terrariums in which one condition is different from the basic terrarium.

In this activity, students form teams and each team decides on ONE condition to change — that is, one way that their terrarium will be different from the basic terrarium. They may choose a condition that they think will encourage mold growth or one that they think will inhibit it.

For students who want to inhibit mold growth, we suggest you bring in some kitchen chemicals that can act as preservatives available -- such as salt, sugar, and hot pepper.

Students may suggest adding garden soil or compost to the food to encourage mold growth. Don’t do it! Some soil bacteria (known as anaerobic bacteria) make nasty smells when they break down foods. These anaerobic bacteria thrive in a sealed plastic bag with water and fruit. A mold terrarium with soil will grow mold — but it will also stink!

If you think your students will come up with ideas that you can’t accommodate with materials on hand, consider splitting the activity into two days. On the first day, complete steps 1 to 6 of the activity, where students brainstorm ideas for their terrarium. Then you can bring in additional materials for the second day (steps 7 to 17), when students set up their terrariums.

Step 3: Print handouts.

Each student needs:

Step 4: Prep before class

Before class, cut up the food that you will be using in your experiment. For each team, prepare a paper plate with a piece of each kind of food that you’ll be testing.

Step 5: Follow up after class

The second page of the student handout lets students record observations of their terrarium over time. This lets them see which food molds fastest in their terrarium. By filling in circles to record how much of a given food is covered with mold, they create a bar graph of the mold growth.

We recommend that you create a bulletin board where you can post results from all the terrariums in the class. By comparing results, students can see which conditions are most conducive to mold growth and answer questions like these:

  • Does the same food mold fastest in all conditions?
  • If you had to take food on a long trip and you had no refrigeration, which of these foods would be the best one to take? How would you store it to keep it fresh as long as you could?
Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Activity: Mold Terrarium
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Beginning Exploration (8 of 8)

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Beginning Complete!

You've completed the Exploration & Activity!

If you have more time, view the assessment, reading and extension activity in the optional extras.

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Optional Extras

Below are ideas for extending this topic beyond the activity & exploration you just completed.
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Activity: Worm Composting

Do the Rot Thing, an activity booklet produced by the Alameda County Waste Management Authority (CA), includes a section on worm composting in your classroom. Get up close and personal with the decomposers that keep our planet healthy.

Learn more about worms from University of Illinois’ online resource, The Adventures of Herman (the Worm). Available in English and Spanish.

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Readings

These Common-Core-aligned readings are free with registration on ReadWorks. All include comprehension questions.

The ancient Egyptians made mummies by using salt to keep mold from growing. Read about animal mummies in Pet Cemetary. (grade 5)

Learn how people kept food cold before they had refrigerators in Ice Harvest. (grade 6)

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Video: When Good Food Goes Bad

These dramatic time-lapse videos show what happens to fruit as it molds.

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Video: Indiana Jones of fungus hunters

Dr. Gary A. Strobel is known as the Indiana Jones of fungus hunters. He searches the world’s forests for fungi that live inside plants. Many of these fungi produce chemicals that protect the plants from disease and infection. In the laboratory, Strobel tests these chemicals to see if they can be as useful to people as they are to the plants that they come from. By doing this, he has found chemicals that save lives.

To learn about his work, watch from 35:30 to 37:40 in Nature’s Great Decomposers, a 45-minute documentary on NatGeo TV.

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FAQ

Looking for answers to some frequently asked questions about mold? You've come to the right place.

These answers are from the Mad Scientists Network, a collective of smart scientists who aren't really mad at all.

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Discuss: Science & History

How did people keep food from spoiling before they had refrigerators? Ask your students for ideas. Here are some questions to get them thinking — with links for further research.

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Image & Video Credits

Mystery Science respects the intellectual property rights of the owners of visual assets. We make every effort to use images and videos under appropriate licenses from the owner or by reaching out to the owner to get explicit permission. If you are the owner of a visual and believe we are using it without permission, please contact us—we will reply promptly and make things right.

Exploration
leaves on cement by Kichigin
walking through leaves by Suzanne Tucker
kid playing in leaves by Chris Nolan , used under CC BY
wintery road by David Merrigan , used under CC BY
spring/green road by artens
bag of leaves by MiVa
leaves by Albert Bridge , used under CC BY-SA
walking on log-leaves by unsplash
leaf decomposition by Josh Williams
fungus mycelium by Kris H. Light
second log flip by Sergei A. Polozov
growing mycelium by franchise films
mushroom time lapse by OddScience
mushroom time lapse 2 by franchise films
fungi mycelium on wood by chanus
hands dug into work by 13Imagery
decomposition by StopWaste
Russula by Jerzy Opioła , used under CC BY-SA
cinnabar-red chanterelle by Jake Stookey
red capped mushrooms by Gemini78
yellow & white capped mushrooms by Kurt Bauschardt , used under CC BY-SA
mushroom by Mary Smiley , used under CC BY-SA
white mushroom by arhendrix
orange mushrooms by Mushroom Observer , used under CC BY-SA
Cordyceps_locustiphila_Henn by Mushroom Observer , used under CC BY-SA
mycelium growing more by Jerzy Opioła , used under CC BY-SA
trees broken up by shore by skeeze , used under Public Domain
man hiking by Poprotskiy Alexey
mushrooms growing outside complex by Vasile Cotovanu , used under CC BY-SA
forest floor by Alessandro Colle
pinic table lunch by adriaticfoto
moldy bread by Taborsky
moldy strawberries by rsooll
mycelium on potato by Telia
mycelium in orange substance by Irina Kozorog
moldy orange by Irina Mos
mushroom cap by Aleksey Gnilenkov
casual living room by Wonderlane
berry decomposition by webiocosm
compost bin by Evan Lorne
inside of compost bin by BMJ
woman inside grocery store by Adam Melnyk
moldy tomatoes by Comrade Foot
inside of fridge by thodonal88
camping- tent by Milaniphotography
Activity
black electric heater by ronstik
hands by photka
pencil by JohannPoufPouf
hands up by Rawpixel.com
Other
Unit: leaf by LilKar
Unit: leaf 2 by Etakundoy