There is an incredible 100,000 species of organisms which are classed as fungi and are divided into 4 groups. These are known as: Zygomycota, Ascomycota, Basidiomycota, and Deuteromycota.
Zygomycota Commonly known as the bread molds, such as those of the genus Glomus, that form important symbiotic partnerships with plants. Most are soil-living saprobes that feed on rotting matter. Some are parasitic of plants or insects. They reproduce sexually and form tough zygospores from the joining together of nearby gametangia. There is no distinguishable male or female. Zygospore formation was the first activity to be used as evidence for sexuality in fungi.
Ascomycota. Known as the sac fungi, it is the largest divison of fungi and includes yeasts, the powdery mildews, the black and blue-green molds, edible types such as the morel and the truffle, and species that cause different diseases of plants such as Dutch elm disease and chestnut blight. There are over 50,000 species, about 25,000 of which occur only in lichens. Their life cycle is a complicated arrangement of sexual and asexual reproduction.
Basidiomycota This makes up about 37% of fungi. This group describes a wide variety of organisms and it has been estimated that there is over 30,000 species and there are more being discovered every day. It includes most mushrooms, bracket fungi (the stuff that grows like little shelves on trees) an edible kind called the Tuckahoe and the puffballs.It also includes the parasitic fungi that causes smut and rust in plants. The method of reproduction is a propelling of spores directly into the air. These spores may be sexual or asexual. One of the unusual formations of Basidiomycota are known as fairy rings. Fungi grows on dead leaves and roots, and produce rings of mushrooms. The rings get bigger every year and release nutrients into the soil, creating very lush grass. Folkloric legends associated these rings with fairy dances.
While mushrooms are used for food, there are also many other uses humans have for Basidiomycota. For example, the toxin phalloidin, found in the mushroom, is used in fluorescent stains that are used by cell biologists to view the cytoskeleton. Certain wood-decaying enzymes are used in paper production. Some people use mushrooms for hallucinogenic purposes.
Deuteromycota This makes up a proportion of fungi which does not fit into the other groups. The one thing they have in common is a lack of sexual reproductive features. Although it is generally believed that this group do in fact belong to the Ascomyota and Basidiomycetes group of fungi and the apparent lack of reproduction is in fact merely a non sexual stage. The group includes species that help create Roquefort and Camembert cheeses, that cause diseases of plants and of animals for example, athlete's foot and ringworm, it also includes the fungi that produce penicillin.
The study of fungi is a fascinating one and new discoveries and insights are being made on a regular basis. At the moment more insight is needed on their reproductive methods which are very complex. This would help greatly in classification of species.