Classification of the Fungi

If you had to guess, would you say a fungus is a plant or an animal? Scientists used to debate about which kingdom to place fungi in. Finally they decided that fungi were plants. But they were wrong. Now, scientists know that fungi are not plants at all. Fungi are very different from plants.

The main difference between plants and fungi is how they obtain energy. Plants are autotrophs, meaning that they make their own "food" using the energy from sunlight. Fungi are heterotrophs, which means that they obtain their "food" from outside of themselves. In other words, they must "eat" their food like animals do. But they don't really eat. Instead, they absorb their nutrients.

Yeasts, molds, and mushrooms are all different kinds of fungi. There may be as many as 1.5 million species of fungi (Figure below). You can easily see bread mold and mushrooms without a microscope, but most fungi you cannot see. Fungi are either too small to be seen without a microscope, or they live where you cannot see them easily—deep in the soil, under decaying logs, or inside plants or animals. Some fungi even live in, or on top of, other fungi.

Fungi are Good Eaters

Fungi can grow fast because they are such good eaters. Fungi have lots of surface area, and this large surface area “eats” or absorbs. Surface area is how much exposed area an organism has, compared to their overall volume. Most of a mushroom's surface area is actually underground. If you see a mushroom in your yard, that is just a small part of a larger fungus growing underground.

These are the steps involved in fungi "eating":

1. Fungi squirt special enzymes into their environment.

2. The enzymes help digest large organic molecules, similar to cutting up your food before you eat.

3. Cells of the fungi then absorb the broken-down nutrients.