Concept preview

What you will be able to do

1. 01Describe the fungal body plan built from hyphae and mycelium.
2. 02Explain why fungal cell walls are made of chitin rather than cellulose.
3. 03Explain absorptive, saprotrophic nutrition and extracellular digestion.
4. 04Distinguish yeasts from moulds and explain the role of fruiting bodies.

When you picture a fungus you probably think of a mushroom, but that is a little like judging an apple tree by a single apple. The mushroom is only the temporary reproductive structure; the true body of the fungus is a vast, hidden web of microscopic threads spreading unseen through the soil, the wood, or the bread beneath it. Each thread is called a hypha (plural hyphae), and a whole tangled network of them is a mycelium. This is one of the most important ideas in all of fungal biology: a fungus is not a plant-like solid with roots and leaves, but a branching filamentous body designed for one purpose above all — to reach through its food and grow into it. A single mycelium exploring a rotting log may contain kilometres of hyphae packed into a few grams of wood, and the largest known fungal individual, a honey fungus in Oregon, spreads its mycelium across several square kilometres of forest floor, making it one of the largest living things on the entire planet. Understanding fungi begins with abandoning the mushroom and learning to see the thread.