Phylogeny and classification of fungi
From VASATWiki
Retrieved from Wikipedia:http://en.wikipedia.org/wiki/Fungal
Fungi were originally classified as plants, however they have since been separated as they are heterotrophs. This means they do not fix their own carbon through photosynthesis, but use carbon fixed by other organisms for metabolism. Fungi are now thought to be more closely related to animals than to plants, and are placed with animals in the monophyletic group of opisthokonts. For much of the Paleozoic Era, the fungi appear to have been aquatic. The first land fungi probably appeared in the Silurian, right after the first land plants appeared even though their fossils are fragmentary. For some time after the Permian-Triassic extinction event, the fungi went into a fungal spike because they were the dominant life forms - nearly 100% of the available record.Fungi absorb their food while animals ingest it; also unlike animals, the cells of fungi have cell walls. For these reasons, these organisms are placed in their own kingdom, Fungi, or Eumycota.
The Fungi are a monophyletic group, meaning all varieties of fungi come from a common ancestor. The monophyly of the fungi has been confirmed through repeated tests of molecular phylogenetics; shared ancestral traits include chitinous cell walls and heterotrophy by absorption, along with other shared characteristics.
The taxonomy of the Fungi is in a state of rapid flux at present, especially due to recent papers based on DNA comparisons, which often overturn the assumptions of the older systems of classification. There is no unique generally accepted system at the higher taxonomic levels and there are constant name changes at every level, from species upwards. Fungal species can also have multiple scientific names depending on its life cycle. Web sites such as Index Fungorum, ITIS and Wikispecies define preferred up-to-date names (with cross-references to older synonyms), but do not always agree with each other or with names in Wikipedia in its various language variants.
[edit] Types of fungi
The major divisions (phyla) of fungi are mainly classified based on their sexual reproduction|reproductive structures. Currently, five divisions are recognized:
- The Chytridiomycota are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own through liquid menstrua by simple flagella.
- The Zygomycota are known as zygomycetes and reproduce sexually with meiospores called zygospores and asexually with sporangiospores. Black bread mold (Rhizopus stolonifer) is a common species that belongs to this group; another is Pilobolus, which shoots specialized structures through the air for several meters. Medically relevant genera include Mucor, Rhizomucor, and Rhizopus. Molecular phylogenetic investigation has shown the zygomycota to be a polyphyletic group.
- Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually. This is an ancient association, with evidence dating to 400 million years ago.
- The Ascomycota, commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, some mushrooms and truffles, as well as single-celled yeasts and many species that have only been observed undergoing asexual reproduction. Because the products of meiosis are retained within the sac-like ascus, several ascomyctes have been used for elucidating principles of genetics and heredity (e.g. Neurospora crassa).
- Members of the Basidiomycota, commonly known as the club fungi or basidiomycetes, produce meiospores called basidiospores on club-like stalks called basidia. Most common mushrooms belong to this group, as well as rust (fungus) and smut fungi, which are major pathogens of grains.
Although the water molds and slime molds have traditionally been placed in the kingdom Fungi and those who study them are still called mycologists, they are not true fungi. Unlike true fungi, the water molds and slime molds do not have cell walls made of chitin. In the 5-kingdom system, they are currently placed in the kingdom Protista. Water moulds are descended from algae, and are placed within the phylum Oomycota, within the Kingdom Protista.
