Ascomycota p. p.
Saccharomycotina (true yeasts)Taphrinomycotina p. p.Schizosaccharomycetes (fission yeasts)Basidiomycota p. p.
Agaricomycotina p. p.TremellomycetesPucciniomycotina p. p.MicrobotryomycetesYeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. ...
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The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.
Yeasts are unicellular organisms that evolved from multicellular ancestors, with some species having the ability to develop multicellular characteristics by forming strings of connected budding cells known as pseudohyphae or false hyphae. Yeast sizes vary greatly, depending on species and environment, typically measuring 3–4 µm in diameter, although some yeasts can grow to 40 µm in size. Most yeasts reproduce asexually by mitosis, and many do so by the asymmetric division process known as budding. With their single-celled growth habit, yeasts can be contrasted with molds, which grow hyphae. Fungal species that can take both forms (depending on temperature or other conditions) are called dimorphic fungi.
