8.3: Fungi Classification

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What type of fungus is this?

Obviously a mold. But what type of mold? There are thousands of known species of molds. How are they classified?

Classification of Fungi

For a long time, scientists considered fungi to be members of the plant kingdom because they have obvious similarities with plants. Both fungi and plants are immobile, have cell walls, and grow in soil. Some fungi, such as lichens, even look like plants (see Figure below).

The Kingdom Fungi

Today, fungi are no longer classified as plants. We now know that they have unique physical, chemical, and genetic traits that set them apart from plants and other eukaryotes. For example, the cell walls of fungi are made of chitin, not cellulose. Also, fungi absorb nutrients from other organisms, whereas plants make their own food. These are just a few of the reasons fungi are now placed in their own kingdom.

Fungal Phyla

Classification of fungi below the level of the kingdom is controversial. There is no single, widely-accepted system of fungal classification. Most classifications include several phyla (the next major taxon below the kingdom). Three of the most common phyla are compared in Table below.

Phylum	Description	Example
Zygomycota	mainly terrestrial, live in soil and compost and on foods such as bread	black bread mold
Basidiomycota	have many different shapes, considerable variation exists even within species	button mushrooms
Ascomycota	found in all terrestrial ecosystems world-wide, even in Antarctica, often involved in symbiotic relationships	baker’s yeast

Summary

Fungi used to be classified as plants. Now, they are known to have unique traits that set them apart from plants. For example, fungal cell walls contain chitin, not cellulose, and fungi absorb food rather than make their own.
Below the level of the kingdom, classification of fungi is controversial.

Review

State why fungi were once classified as plants.
Explain the significance of the chitin cell wall of fungi.
Mushrooms belong to what phylum of fungi?

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	[Figure 2]	Credit: Flickr:SNappa2006 Source: http://www.flickr.com/photos/snappa2006/4343940216/ License: CC BY 2.0
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