The Fungus Kingdom

A kingdom of their own

Scientists sort all living things into big groups called kingdoms. For a long time, people thought there were only two: plants and animals. Fungi got lumped in with plants because they seem to grow out of the ground and stay in one place.

But fungi are not plants at all. Today scientists give fungi their own kingdom: Fungi. It sits between plants and animals, and in some ways it is actually closer to us animals than to plants.

Why fungi are not plants

Plants are producers. They make their own food from sunlight using a green pigment called chlorophyll, in a process called photosynthesis. Fungi have no chlorophyll and cannot photosynthesize. They cannot make their own food.

Instead, fungi are decomposers and feeders. They release special juices called enzymes onto their food. The enzymes break the food into tiny pieces, and the fungus absorbs those pieces. This is called absorptive nutrition — digesting food on the outside, then soaking it up.

A surprising building block

Here is a clue that fungi are not plants. Plant cell walls are made of a material called cellulose. Fungal cell walls are made of chitin (say it: KY-tin).

Chitin is the same tough material that forms the shells of beetles, crabs, and other insects. So the wall around a fungus cell is more like a beetle shell than a blade of grass. That is one reason scientists say fungi are closer to animals than to plants.

So what is a fungus?

Let's gather the evidence:

• No chlorophyll — it cannot make food from sunlight.

• Absorbs food using enzymes, the way animals digest food (but on the outside).

• Cell walls of chitin, like insect shells, not cellulose like plants.

• Grows as a web of threads called hyphae, which together form mycelium.

Fungi include mushrooms, molds, mildews, and yeasts. Some are microscopic. Some, like the honey fungus, are among the largest living things on Earth.

Safety first: knowing the science does not make wild mushrooms safe to eat. Many are toxic and look like edible ones. Never pick and eat wild mushrooms without an expert adult. Our grow kits use known-safe, edible species.