BACKGROUND:
How many times have you looked for an
orange to eat and found that the last one left had grown soft, blue-green
fuzz? Have you ever left a wet towel at the bottom of your clothes hamper and
at the time of washing you found that it had green "freckles" all
over it? Or how many times have you found bread that has gone stale and has
grown black "whiskers?" The green fuzz on the orange, the green
freckles on the towel and the black whiskers on the bread are all known as
molds. Molds are really tiny fungi belonging to one of the 5 kingdoms.
"Molds" are a term that is not really a natural grouping, but until
scientists figure out exactly where they belong, we will consider them fungi.
Molds are so tiny that we cannot see them unless there are many of them
bunched together. To see just one mold you need a microscope. There are many
kinds of molds. One of the most common molds is the one which turns oranges
into green fuzzy balls. It is called penicillium. This is where the drug
penicillin comes from.
Plants use sunlight to make food in their
leaves. The green coloring matter acts as a kind of food factory. Molds have
no food factories, so they take the food they need from their host. All molds
are food robbers.
Foods will eventually rot if not kept cool
or not eaten within a certain time unless frozen. The more time food stays
around the more of a chance spores from a mold have of landing on it and
growing. A spore is the reproductive part of the fungi.
Wherever there is food, air, and moisture,
some mold spores will find their way there to settle and begin to grow. If a
spore doesn't find the food, air or moisture it needs to grow it does not die.
It just waits. It can remain alive for years in its case, waiting for the
right conditions to burst open and grow.
PROCEDURE:
- Review with students the different
kingdoms and their characteristics. You may want to review some of the lower
grade material if your students have not developed a feeling for the diversity
of life. In this unit, students will look at organisms that they see, but
rarely think about as being living.
- In a large zip lock bag, place a fresh
orange and a "molded" orange and then seal the bag. In another bag,
place another molded orange and seal the bag. Place a fresh orange besides the
bag with only the molded orange. Place both sets in separate dark, warm areas
in the room. Have students predict which will grow mold first. You may want to
put other materials next to the bags and observe what happens. For example can
plastic become infected or can different types of bread get moldy faster than
others?
- Use the worksheet for students to
identify the types of rot they discovered.. Lots of Rot can also help
students identify what they have found.
