Their lack of sexual stages was the basis for them being called fungi imperfecti in the past.
Most Deuteromycota have only asexual reproduction as the sexual stage of the life cycle has been lost or has yet to be discovered.
There are a great number of human uses for these fungi; most significant is the production of antibiotics for medicinal use. These substances are produced by the fungus to inhibit the growth of other living organisms around themin particular, disease-causing bacteria. These substances are extracted from the fungus and are used to kill bacteria in the human body.
Economically important imperfect fungi are Penicillium and Aspergillus.
The fungal group Basidiomycota, also known as the club fungi, includes some of the most familiar fungi.
Basidiomycetes play a key role in the environment as decomposers of plant litter. They are distinguished from other fungi by their production of basidiospores, which are borne outside a club-shaped, spore-producing structure called a basidium. These spores rarely germinate or mature.
For example, Agaricus (mushroom), Ustilago (smut), and Puccinia (rust fungus).
The sac-fungi produce spores in small cup-shaped sacs called asci, hence the name ascomycota.
The mature sac fungi spores are known as ascospores, they are released at the tip of the ascus breaks open.
Yeast is the most common one-celled fungi. Yeast reproduces through asexual process called budding. The buds form at the side of the parent cell, they pinch-off and grow into new yeast cell which is identical to the parent cell.
For example, Aspergillus, Claviceps, Neurospora.
The fungal group Zygomycota is most frequently encountered as common bread molds, although both freshwater and marine species exist.
Most of these live on decaying plant and animal matter found on the substrate.
They are usually recognized by their profuse, rapidly growing hyphae, but some exhibit a unicellular, yeast-like form of growth.
Asexual reproduction is by means of spores produced in sporangia borne on the hyphae.
For example, Mucor, Rhizopus (the bread mould) and Pilobolus.