give the list of organisms belonging to the class phycomycetes and the diseases caused by them
Answers
Answer:
Explanation:
Phycomycetes is an obsolete[1][2][3] polyphyletic taxon for certain fungi with aseptate hyphae.[4] It is used in the Engler system.[5]
The class Phycomycetes has been abolished and in its place exists Zygomycetes, Chytridiomycetes, Plasmodiophoromycetes, Hyphochytridiomycetes, Trichomycetes (including Harpellales, Asellariales, Eccrinales and Amoebidiales) and Oomycetes. Still, "Phycomycetes" can be used to refer to all the above-mentioned classes as a whole.
The members of this group are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants. The mycelium is aseptate and coenocytic. Asexual reproduction by zoospore or by aplanospore. A zygospore is formed by the fusion of two gametes. Examples are Mucor, Rhizopus, Albugo, Saprolegnia, soham.
Molecular phylogenetic analysis confirmed the phylum Zygomycota to be polyphyletic, and the taxa conventionally classified in Zygomycota are now distributed among the new phylum Glomeromycota and 4 subphyla incertae sedis (uncertain placement). Because the nomenclature of the disease zygomycosis was based on the phylum Zygomycota (Zygomycetes) in which the etiologic agents had been classified, the new classification profoundly affects the name of the disease. Zygomycosis was originally described as a convenient and inclusive name for 2 clinicopathologically different diseases, mucormycosis caused by members of Mucorales and entomophthoramycosis caused by species in the order Entomophthorales of Zygomycota. Without revision of original definition, the name “zygomycosis,” however, has more often been used as a synonym only for mucormycosis. This article reviews the progress and changes in taxonomy and nomenclature of Zygomycota and the disease zygomycosis. The article also reiterates the reasons why the classic names “mucormycosis” and “entomophthoramycosis” are more appropriate than “zygomycosis.”
Before Whittaker created the kingdom Fungi in 1969 [1], the agents causing mucormycosis, entomophthoramycosis, and other fungi that produce coenocytic (aseptate) vegetative hyphae and sexual spores called “zygospores” or “oospores” were classified in the Phycomycetes of the subdivision Thallophyta in the plant kingdom [2]. The taxonomy of the fungi during that era was based on the morphologic similarities of sexual reproductive structures, and 3 classes were recognized: Phycomycetes, Ascomycetes, and Basidiomycetes. Those species that reproduced only by asexual spores were grouped in the form-class Deuteromycetes, or Fungi Imperfecti [3]. As the knowledge on life cycle, ecology, nutritional modes, ultrastructure, and other aspects of the organisms increased, taxonomists attempted to place organisms in the taxa that more closely reflected their hypothetical evolutionary relationships. As a result, fungi acquired their own kingdom (kingdom Fungi) and underwent significant changes in classification. Because Phycomycetes comprised a miscellaneous assemblage of evolutionarily unrelated organisms, the class Phycomycetes was abolished [1], and the members of Phycomycetes were accommodated in a series of classes: Zygomycetes, Chytridiomycetes, Hypochytridiomycetes, Trichomycetes, and Oomycetes [3]. Further classification of the fungal kingdom on the basis of shared, derived characters delimited the kingdom to include only Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota, and this classification scheme has been universally accepted until a decade ago (Figure 1A). The phylum Zygomycota contained Mucorales, Entomophthorales, and 8 other orders [4].
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Figure 1.
Old (A) and a proposed new (B) classification schemes of the kingdom Fungi.
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TAXONOMY OF ZYGOMYCOTA