Classification Of Fungi Alexopoulos And Mims 1979 Pdf 27l
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There is no universally accepted classification of fungi. Some taxonomic schemes are intuitively appealing, but their hierarchical organization is based on little more than personal preference, or it has been imposed without any empirical basis. The most widely recognized classification is that of Hawks, which is also the most recent. It is based on morphological characteristics and considers phylogeny as a secondary consideration, whereas the historical classification of species and varieties is based on similarity, not phylogenetic relatedness.
The evolutionary classification of fungi has been changing at rapid rates due to the discovery and development of new methods for genetic analysis. In the 1980s, comparisons of the nucleotide sequences of ribosomal RNA (rRNA) genes first established that a variety of unicellular fungi form a monophyletic group that is distantly related to plants and animals. Another type of rRNA gene in animals and plants is called small ribosomal RNA (18S RNA) and is commonly used as a molecular marker for phylogenetic analysis. Molecular phylogenetic analyses based on DNA sequences from ribosomal and other genes have helped to develop taxonomic ranks at every phylogenetic level. For example, the phylum Fungi (which was renamed as the kingdom Fungi) is divided into an estimated two million to three million species (or at least 20,000 to 30,000 taxa).[5] The division of the kingdom into the fungal phyla by the evolutionary biologist, plant biologist, and mycologist F. John H. Hawks, Jr., is: Ascomycota, Basidiomycota, Chytridiomycota, Blastocladiomycota, and others.
According to most researchers, higher fungi are the dominant form of life on earth, although much of the speculation about the evolution and biology of fungi has dealt with the implications of this hypothesis for the relationship between living things and the Earth.
The classification of fungi is complicated by the fact that the evolution of fungi has involved a number of independent evolutionary events. The relationships between the different kingdoms of eukaryotes have been the subject of debate since their original classification by Antony van Leeuwenhoek in 1683. Initially fungi were thought to be plants and subsequently were considered protozoans. For many years, however, fungi were misclassified as protozoa, even though they are distinct eukaryotic kingdoms with specific morphologies, life cycles, cell structures, and even cell types. Over time, the increasing wealth of molecular and phylogenetic data[151] has led to the increasing recognition of fungi as a kingdom in their own right. The earliest molecular phylogenetic studies of fungi supported the grouping of fungi with the protozoans, but more recent studies, particularly based on large scale analyses of gene sequences from both nuclear and organellar genomes, have demonstrated that fungi are a monophyletic group by themselves. 827ec27edc