Tuesday, December 6, 2011

Fungi


The fungi lack photosynthetic pigments. As a group, they are heterotrophic and must obtain their food either from dead organic matter (saprophytically) or from living organisms (parasitically). Approximately 100,000 species have been described, and these are very widely distributed, particularly on land, although there are a number of common water-growing species.
What were once fungi have been divided into six phyla: Myxomycophyta and Chytridomycota (now in kingdom Protista), Oomycota (now in kingdom Chromista), and Zygomycota, Ascomycota, and Basidiomycota (the true kingdom Fungi). Classification of the three phyla of true fungi is controversial and based primarily on their sexual reproduction. A seventh artificial phylum, Deuteromycota, includes all species for which no sexual stages are known at present. Mycologists consider it their duty to discover the sexual stages and classify these species into the natural phyla...easier said than done. Most are clearly members of Ascomycota and a few are clearly members of Basidiomycota.
The true fungi produce a vegetative body which is composed of masses of fine branched filaments often having a cottony appearance. A single filament is called a hypha, while a mass of hyphae makes up the mycelium. Mycelia may form reproductive structures, usually both asexual and sexual. While the mycelia of different species are very much alike in gross appearance, the reproductive structures are distinctive.
You will look at a few rather typical representatives of kingdom fungi. Make a record that will give some idea of the diversity of form that occurs among the fungi and will point out some of the differences among the kinds of fungi. You should practice making life cycle diagrams for these taxa as good practice in understanding their natural history.

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