Main->Readings->5th Grade Readings->Simple Living Things->Part 2
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Even though mushrooms grow from the soil, cannot move about on their own, and look as if they might be plants, they are not plants. They are fungi, a type of living thing which may have been around as long as 900 million years. Fungi belong to a separate kingdom of their own, for many reasons.
One important way fungi are different is the way they eat. Plants make their own food, using chlorophyll, sunlight, water, and carbon dioxide. Fungi cannot make their own food because they do not have chlorophyll. They must eat other living or once-living matter.
Animals eat other living or once-living things too, but fungi are not the same as animals, either. Fungi do eat other living or once-living things, but they do not have stomachs. Fungi live in their food. They absorb it with their surfaces, and when they need more food, they just grow out further to touch more food.
Some fungi get their food from things that once were alive, such as dead trees. They help to break down dead things into soil. Organisms which break down dead matter are called decomposers [dee-com-POE-zurs].
Other fungi get their food by growing on other living things. If an organism lives on and harms another living thing, we call it a parasite (PAR-uh-site). The organism a parasite lives on is called a host.
There are many different types of fungi, including molds, yeasts, and mildew. Some of these fungi, such as yeast, are one-celled. Others, such as mushrooms, are many-celled.
In the supermarket, you may see boxes of mushrooms for sale. These mushrooms are usually white or very light. They have umbrella-like caps with feathery gills on the underside, on top of a central stalk. Yet most mushrooms do not look anything like this. The ones you see in stores belong to only one order of mushrooms (the agaricales) and are usually only one type, the "button" mushroom. Mushrooms may take many other forms, many of them very unusual. They can look like wood, scrambled eggs, lumps of dirt, scales, or even brains, but you do not see those in the grocery store.
The mushroom you can see on the surface is actually just the "fruiting body" of the fungus. It only exists for part of the fungus life cycle. A fruiting body is the part of the fungus which makes and releases tiny spores, so the fungus can reproduce. Fungus spores are everywhere, especially in the air, hundreds of thousands of them in the air around you right now. A spore is a single cell that can grow into a new organism.
The main body of the fungus is not the mushroom, but many tiny threadlike structures called hyphae. If you see a mushroom on a fallen log, the hyphae are spread through the log in a mat of fibers. We call the whole collection of fibers of one individual fungus the mycelium. The mycelium is much bigger than its mushroom. There is a fungus in Michigan whose mycelium covers about 40 acres, and one in Washington State which may be up to 2 1/2 square miles.
Take a walk through the woods when it is nice and damp outside and look for mushrooms. Take a field guide with you (never eat mushrooms you find in the wild, because many are poisonous). You will be surprised at what you find. There are mushrooms everywhere, growing from trees and logs, and pushing up from under the leaves. Yet remember that the mushrooms you see are only a tiny part of the whole fungus.
When you keep a loaf of bread on the shelf too long, you may notice green spots on it. Then you have to throw the bread away because it is moldy. Mold is also a fungus. Like the mushroom, it is made of many tiny threads or hyphae. Unlike the mushroom, mold does not have a large fruiting body. It simply grows hyphae up into the air in order to release its spores.
Mold may destroy bread, but it can also save lives. The drug penicillin, which saves many lives by killing bacteria, was discovered by Alexander Fleming in 1928 when he noticed that some mold in a dirty lab dish was keeping bacteria from growing.
Yeasts are another kind of fungus, but unlike molds and mushrooms yeasts are single-celled organisms. Some yeasts can cause infections in human beings.
Other yeasts are very important to human life in another way. When a baker mixes yeast with water and a bit of sugar, the yeast wakes up, eats the sugar, and breathes out carbon dioxide. Meanwhile, the baker mixes the yeast with flour and works it thoroughly into the dough. The yeast makes tiny bubbles in the dough, filling it with gas. Then the baker pops the dough in the oven and bakes it, killing the yeast but leaving the holes behind. Yum--a nice fresh loaf of bread, made with fungus.
As you can see, fungi are everywhere and in every part of our lives. For instance, mildew are fungi that grow on the surface of things. An example is the white covering over lilac leaves in the early fall.
Also, there are fungi on the roots of many plants. However, in this case, the fungus is not bad. The plants and the fungus are working together. The fungus helps the plant get minerals, and the plant feeds the fungus. These plants need the fungus in order to be healthy. Fungi are used to make cheese, but they also cause the annoying diseases of athletes foot and ringworm.
One of the most important things fungi do is something that might not be obvious at first. Because fungi often feed on once-living things, they help break down materials and return them to the earth so other organisms can use them again. Without fungi and other decomposers, dead plants and animals would just lie there forever, so making things rot is a public service! Fungi, the third kingdom of living things, are very important to all life on earth.
The next two kingdoms of living things we will study are just as important as the fungi, but you cannot see them. They are so small that without a microscope we would not know they were there. They are the protists and the monerans.
Go on to Part 3: Protists
This page last modified on August 15, 2002