Fungi and protists, including mold, moss, yeast, and mushrooms, are found all around us. One common group of fungi is mold. Mold, like all fungi, are heterotrophs, which means they rely on other living things for their energy. This is different than an autotroph like a plant, which gets its energy from the sun.
Mold commonly grows on bread, getting food from this source. What do you think makes mold grow? Being in a dark place? Being exposed to moisture? Something else? The scientific method is a series of steps some scientists use to answer question and solve problems. To conduct an experiment based on the scientific method, you must have a control sample, which has nothing done to it, and several experimental samples, which have changes made to them. You can then observe results in the experimental sample to see how your changes to them affect results.
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- paper towel
- slices of bread
- plastic wrap
- pie dish or plate
- microscope with slides and coverslips (optional)
Here’s what you do:
- Place a wet paper towel on the bottom of a pie tin
- Add a slice of bread
- Cover with plastic wrap and place in a dark place for three days
- Take the pie tin out and make observations
- What organisms do you think you see?
In the dark environment, mold grows on the bread. The exact type of mold will be different depending on the type of bread. Is there a difference between white and wheat? Organic and Wonder Bread? Now let’s take this a step further:
- Take five pieces of bread. Place one in a pie tin and leave it on the kitchen counter. This is your “control” bread.
- Place the other pieces of bread in pie tins and do something you think will help make mold grow. These are experimental samples.
- Every day, observe each slice of bread and take notes.
- What made the mold grow fastest? Did anything slow down mold growth, and form less mold than the control?
- What does this tell us about food storage?
You probably found that mold grows well in the dark, and warm conditions. So, if you want to make your bread last longer, keep it cool and out of the dark.
Build an Ecosystem
Protists can be classified as animal-like, plant-like, and fungus-like. Animal-like protists are able to move and are heterotrophic, relying on other organisms for food. Many protozoa live in grasses, especially those found in lakes, rivers, and streams, where they are able to get the nutrients they need to survive. Create your own mini-ecosystem of these remarkable creatures in the activity below.
- clean, empty glass jar
- microscope with slides (optional)
- Add water and a handful of grass to the jar
- Put the lid on the jar but don’t seal it all the way
- Keep the jar in a dark area for three days
- Take it out and make observations. If possible, observe the organisms under a microscope.
Protozoa and other protists live of the grass, and increase in number after the jar is in the dark for several days.
Fun with Yeast
There are over 1,500 species of yeast currently discovered, and scientists estimate that this is only 1% of all yeast species. Most reproduce by budding, although a few use mitosis. Most yeasts are single-celled, although the multicellular varieties use a string to connect budding cells (pseudohyphae or false hyphae). Yeast is a fungus used in cooking many products, including bread. Why is yeast important in the baking process? Let’s find out!
- zipper-type sandwich bag
- warm water
- Put about a teaspoon of yeast into a sandwich bag.
- Add about three spoons of sugar and about half a cup of very warm water. If you stick your finger into the water, it should feel warm but comfortable.
- Squeeze out as much air as you can and then seal the bag. Place it in a warm spot
- After about 5 minutes, you should start to see tiny bubbles forming. After 15 minutes, you should see quite a few more bubbles. After an hour, the bag should be inflated quite a bit.
Imagine that the yeast is inside some bread dough instead of the bag. As it changes the flour into sugar and consumes it, it gives off carbon dioxide and alcohol. Your bread will not be alcoholic, but when the alcohol cooks away, it leaves behind flavors that add to the taste of the bread.
What happens if you place leftover food in three different cups and placed one of the cups on a sunny windowsill, another cup in the refrigerator, and a third cup in a dark cupboard? What if you use a magnifier? How does light or temperature affect the mold’s growth? Are the molds all the same color, or are they different?