Introduction to Fungi
The fungi (singular, fungus) include several thousand species of eukaryotic, spore bearing organisms that obtain simple organic compounds by absorption. The organisms have no chlorophyll and reproduce by both sexual and asexual means. The fungi are usually filamentous, and their cell walls have chitin. The study of fungi is called mycology, and fungal diseases are called mycoses. Two major groups of organisms make up the fungi. The filamentous fungi are called molds, while the unicellular fungi are called yeasts. The fungi are classified in the kingdom Fungi in the Whittaker five-kingdom system of classification.
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| Agriraghv |
KEY CONCEPTS
1. Kingdom Fungi (the true fungi) is a monophyletic
group of eukaryotic heterotrophs that reproduce with spores and have chitinous
cell walls. The most familiar fungi are kitchen molds and mushrooms. The
kingdom may include 1.5 million species, of which about 80,000 species have
been named and described.
2. Some fungi destroy crops and stored food. Others
are valuable decomposers or symbionts that cohabit with algae and cyanobacteria
or assist plant growth. Baker's yeast is a fungus, and penicillin is a fungal
product.
3. Most fungi develop a mycelium, composed of
branching threads (hyphae) that collect nutrients and produce reproductive
structures. Some fungi have a simpler thallus or live as microscopic unicells
(yeasts). Dimorphic fungi make both mycelia and yeasts
4. Many fungi
make asexual spores to multiply and sexual spores for diversity. Exceptions
include mushroom fungi, which use sexual spores to multiply, and mitosporic
fungi, which have not been observed to reproduce sexually. However, nearly all
tested fungi show signs of recent genetic recombination.
5. Two large
phyla (Ascomycota and Basidiomycota) contain 95% of named species in kingdom
Fungi and are informally called dikaryomycetes because their sexual life cycle
has a unique dikaryotic stage. The remaining 5% of named species are divided
between three phyla (Glomeromycota, Zygomycota, and Chytridiomycota) and are
informally called coenomycetes because their hyphae lack the regular septation
found in dikaryomycetes.
6. Kingdom Fungi excludes some organisms that
traditionally are called fungi, and adds other organisms that were previously
left out. New studies are changing classification within the kingdom.
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Classification of Fungi Agriraghv |
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