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Cellular
life on earth can be divided in three different domains – the eukaryotic, prokaryotic
and archaea, within these, further sub distinctions can be made. Fungi belong
to the eukaryotic domain, in which they constitute their own kingdom, besides
the plant and animal kingdoms. Similar to other eukaryotic cells, fungi cells contain
organelles plus a true nucleus, all contained within a membrane, while they differ
to prokaryotic and archae cells,  by their
absence of chlorophyll and having a cell wall consisting of chitin . The
general scheme of a fungi is relatively simple. Composing of a main body, a
mycelium, made up by a branched network of tubes, hyphae. Through hyphae,
nutrients are absorbed, in which organic carbon, from either living or dead
biological organisms, function as the main energy source. Reproduction of fungi
can occur in two separate, yet connected, ways. Either reproduction takes place
asexually, mainly through the means of the release of small identical copies of
parent fungi as spores, or reproduction occurs sexually. Sexual reproduction varies
between different phylums and therefore a generic description does not make
sense. Instead a detailed description is integrated within the description of
each phylum.

The fungi
kingdom can be subdivided in 5 different phyla, these are named Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota and Deuteromycota.

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Phylum Chytridiomycota
encompasses most fungi, which at some point in their life cycles exists as flagellated
swimming cells and these fungi are therefore, primarily, found in aquatic
environments. These fungi reproduce asexually when
a zoospore lands on a substrate, followed by formation of a cell wall around it
– leading to creation of a fungi body. Long threads, rhizoids, attach to the substrate
and through these nutrients are absorbed. After a period of feeding, the fungi
body is converted into a sporangium, a structure which contains and
subsequently releases zoospores. Sexual reproduction occurs by fusing zoospores,
thus creating a diploid zygote, which then hardens and creates a
meiosporangium. Later fusing of nuclei create meiospores, which can then swim
away and form a new fungi body. Fungi of this phyla are mostly harmless,
saprotrophic fungi, although a few pathogens such as Batrachochytrium dendrobatidis, which causes chytridiomycosis in amphibious animals
have been found.

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