This colorful bracket fungus doesn't look much like mold. But they have a lot in common. They both break down organic matter to obtain nutrients. They both reproduce by spores. They are both eukaryotic, but they are not plants, and they are definitely not animals. They are both fungi.

What are Fungi?

Ever notice blue-green mold growing on a loaf of bread? Do you like your pizza with mushrooms? Has a physician ever prescribed an antibiotic for you?

If so, then you have encountered
fungi
. Fungi are organisms that belong to the Kingdom Fungi (
Figure
below
). Our environment needs fungi. Fungi help decompose matter to release nutrients and make nutritious food for other organisms. Fungi are all around us and are useful in many ways.

These many different kinds of organisms demonstrate the huge diversity within the Kingdom Fungi.

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.

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.

The blue in this blue cheese is actually mold, which is a fungus.

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.” 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.