Fungi are important organisms and so distinct from plants and animals that they have been allotted a 'kingdom' of their own in our classifications of life on earth.
Fungi v fungi
First, let’s be clear: fungi and Fungi mean different things. The lower case 'fungi' is a general word that refers to organisms that all look and act the same, but are not all related. This group is artificial and includes moulds, yeasts, mushrooms, slime moulds, and water moulds (like Phytophthora, the cause of the Irish potato famine and Sudden Oak Death).
On the other hand, 'Fungi', with a capital 'F', refers to the evolutionary group that includes most of the best known 'fungi': moulds, yeasts, and mushrooms, but not slime moulds or water moulds.
Because all of these organisms superficially resemble each other and all do similar things, they were grouped together within the lower plants, including mosses, liverworts, and ferns, for a very long time.
Fungi are not plants
Well, at least since 1969 when they were first officially recognized as a distinct group. And more recently, using DNA sequences and comparisons of cell structure, we have learned that Fungi are in fact more closely related to animals than they are to plants. Superficially, they remind us more of plants than animals because they don’t move, but scratch the biological surface just a little and that’s just about the only thing they have in common.
How do Fungi eat?
Unlike plants, which make their own food, Fungi are like miniature versions of our stomachs, turned inside-out. Fungi 'eat' by releasing enzymes outside of their bodies that break down nutrients into smaller pieces that they can then absorb. This feeding strategy means that Fungi always live in and on their food.
How is a fungus built?
Fungi come in many different sizes and shapes. Some are single cells called yeasts, while most are built from masses of tiny filaments. During reproduction, portions of these masses of filaments will differentiate from each other to make complex structures that are sometimes called fruiting bodies. These are best known from the mushrooms, like the iconic fly agaric (Amanita muscaria), but many other types of fruiting bodies are made by Fungi.
Reproduction happens by self-cloning or through sex with compatible partners. Mostly this is accomplished by producing lots and lots of spores, which can disperse far and wide and, with luck, find a mate. But fungi don’t have just two sexes (like male and female), instead they have what are called 'mating types', and there can be as many as 20,000 different ones. Not only that but sometimes the filaments that make up the bodies of two individuals will fuse and merge their DNA – an extraordinary way of having sex that neither plants or animals can achieve.
Where does a fungus live?
Everywhere: Antarctica, the Amazon jungle, the Gobi desert, and even all over (and inside) you, just to name a few locations.
Fungi are amazingly well adapted to just about any condition on Earth. But maybe that’s not so surprising – they have had over one billion years to figure it out.
The importance of Fungi
Where to begin? Fungi are tremendously important to human society and the planet we live on. They provide fundamental products including foods, medicines, and enzymes important to industry. They are also the unsung heroes of nearly all terrestrial ecosystems, hidden from view but inseparable from the processes that sustain life on the planet.