Not an Animal

Closer than you might think

Here is a surprise. When scientists read the DNA of fungi, they found that fungi are actually closer cousins to animals than to plants. Fungi and animals share an ancient ancestor and belong to the same broad branch of life. So why aren't fungi simply animals? Because being cousins is not the same as being the same. Fungi break the animal rules in important ways.

Rule 1: animals move to survive

Animals are famous for moving. A fox runs, a fish swims, a worm wriggles. Even animals that seem to sit still, like a barnacle, can move parts of their bodies to grab food. Moving helps animals hunt, escape, and find mates.

A fungus does not move around. The mushroom you see stays rooted to its spot. Fungi do grow and spread, reaching out with tiny threads, but that slow growing is very different from an animal walking, swimming, or flying.

Rule 2: animals ingest their food

Here is the biggest difference of all. Animals eat by ingesting food. That means taking food inside the body, into a mouth and stomach or gut, and digesting it on the inside. When you eat an apple, you swallow it and your insides break it down.

Fungi have no mouth, no stomach, and no gut. A fungus cannot swallow anything. Instead of digesting food inside, a fungus digests it on the outside. It releases special chemicals called enzymes onto its food. The enzymes break the food down into tiny pieces right where it sits, and then the fungus soaks up the freed nutrients through its surface. This is called absorptive feeding: digest outside, then absorb.

So animals bring food in, then digest it. Fungi digest first, then bring the nutrients in. Same goal, opposite order.

Rule 3: cell walls

There is one more clear clue. Animal cells are soft on the outside; they have no cell wall. That softness lets animal bodies be flexible and lets many animal cells move and change shape.

Every fungus cell is wrapped in a tough cell wall. This wall gives the fungus its shape and support, a bit like a suit of armor around each cell. Animals simply do not have this. (Plants have walls too, but made of a different material - which is why walls alone don't make fungi into plants either.)

The verdict

Fungi are our distant cousins, yet they are not animals. They do not move about, they do not ingest and digest food on the inside, and their cells wear tough walls. The fungi slip out of the animal kingdom, just as they slipped out of the plant kingdom.

A quick safety note: because fungi break down all kinds of material, some grow on things that could make us sick. Never taste wild fungi or moldy food to investigate them. Observe with your eyes, not your mouth.