Fungi are the kingdom that is easiest to mistake for plants. In Three Domains and the Kingdoms you saw why they are not: they cannot make food, and they are more closely related to animals.
Key idea
Fungi include yeasts (single cells), molds and mushrooms. They absorb food from what they grow on. Their cell walls contain chitin. Many are decomposers, breaking down dead matter.
Why it works
A fungus releases digestive juices into wood, soil or bread, then absorbs the small molecules that result. Most of a fungus is a hidden web of thin threads called hyphae. A mushroom is only the part that pops up to release spores, a bit like an apple on an apple tree.
| Fungus | What it does |
|---|---|
| Yeast | Breaks down sugar and gives off carbon dioxide gas, which makes bread rise |
| Penicillium mold | Makes penicillin, the antibiotic Alexander Fleming discovered in 1928 |
| Mushrooms and shelf fungi | Break down fallen logs and leaves, returning nutrients to the soil |
| Bread mold | Grows on and spoils old bread |
Worked examples
Worked example: Plant or not?
Is a mushroom a plant?
- Plants make food by photosynthesis; a mushroom has no chlorophyll.
- It absorbs food, and its walls contain chitin.
Answer: No. It is a fungus.
Worked example: Bread
Why does bread dough with yeast rise?
- Yeast cells break down sugar in the dough.
- They give off carbon dioxide gas, which forms bubbles.
Answer: Gas from the yeast puffs it up.
Common mistake
Thinking mushrooms are plants. Fungi have no chlorophyll and cannot make food, and the mushroom is only a small part of a fungus whose threads spread through soil or wood. Check: does it need light to grow? Fungi do not.