Biological classification of Listeria
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy.
Modern biological classification has its root in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the Darwinian principle of common descent. Molecular phylogenetics, which uses DNA sequences as data, has driven many recent revisions and is likely to continue to do so. Biological classification belongs to the science of biological systematics.
Classification has been defined by Mayr as "The arrangement of entities in a hierarchical series of nested classes, in which similar or related classes at one hierarchical level are combined comprehensively into more inclusive classes at the next higher level." A class is defined as "a collection of similar entities", where the similarity consists of the entities having attributes or traits in common.
What makes biological classification different from other classification systems (e.g. classifying books in a library) is evolution: the similarity between organisms placed in the same taxon is not arbitrary, but is instead a result of shared descent from their nearest common ancestor. Accordingly, the important attributes or traits for biological classification are 'homologous', i.e., inherited from common ancestors. These must be separated from traits that are analogous. Thus birds and bats both have the power of flight, but this similarity is not used to classify them into a taxon (a "class"), because it is not inherited from a common ancestor. In spite of all the other differences between them, the fact that bats and whales both feed their young on milk is one of the features used to classify both of them as mammals, since it was inherited from a common ancestor(s).
Determining whether similarities are homologous or analogous can be difficult. Thus until recently, golden moles, found in South Africa, were placed in the same taxon (insectivores) as Northern Hemisphere moles, on the basis of morphological and behavioural similarities. However, molecular analysis has shown that they are not closely related, so that their similarities must be due to convergent evolution and not to shared descent, and so should not be used to place them in the same taxon.
A classification, as defined above, is necessarily hierarchical. In a biological classification, rank is the level (the relative position) in a hierarchy. (Rarely, the term "taxonomic category" is used instead of "rank".) There are seven main ranks defined by the international nomenclature codes: kingdom, phylum/division, class, order, family, genus, species. "Domain", a level above kingdom, has become popular in recent years, but has not been accepted into the codes.
The most basic rank is that of species, the next higher is genus, and then family. Ranks are somewhat arbitrary, but hope to encapsulate the diversity contained within a group — a rough measure of the number of diversifications that the group has been through.
The International Code of Zoological Nomenclature defines rank, in the nomenclatural sense, as:
Source: http://en.wikipedia.org
Modern biological classification has its root in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the Darwinian principle of common descent. Molecular phylogenetics, which uses DNA sequences as data, has driven many recent revisions and is likely to continue to do so. Biological classification belongs to the science of biological systematics.
Classification has been defined by Mayr as "The arrangement of entities in a hierarchical series of nested classes, in which similar or related classes at one hierarchical level are combined comprehensively into more inclusive classes at the next higher level." A class is defined as "a collection of similar entities", where the similarity consists of the entities having attributes or traits in common.
What makes biological classification different from other classification systems (e.g. classifying books in a library) is evolution: the similarity between organisms placed in the same taxon is not arbitrary, but is instead a result of shared descent from their nearest common ancestor. Accordingly, the important attributes or traits for biological classification are 'homologous', i.e., inherited from common ancestors. These must be separated from traits that are analogous. Thus birds and bats both have the power of flight, but this similarity is not used to classify them into a taxon (a "class"), because it is not inherited from a common ancestor. In spite of all the other differences between them, the fact that bats and whales both feed their young on milk is one of the features used to classify both of them as mammals, since it was inherited from a common ancestor(s).
Determining whether similarities are homologous or analogous can be difficult. Thus until recently, golden moles, found in South Africa, were placed in the same taxon (insectivores) as Northern Hemisphere moles, on the basis of morphological and behavioural similarities. However, molecular analysis has shown that they are not closely related, so that their similarities must be due to convergent evolution and not to shared descent, and so should not be used to place them in the same taxon.
A classification, as defined above, is necessarily hierarchical. In a biological classification, rank is the level (the relative position) in a hierarchy. (Rarely, the term "taxonomic category" is used instead of "rank".) There are seven main ranks defined by the international nomenclature codes: kingdom, phylum/division, class, order, family, genus, species. "Domain", a level above kingdom, has become popular in recent years, but has not been accepted into the codes.
The most basic rank is that of species, the next higher is genus, and then family. Ranks are somewhat arbitrary, but hope to encapsulate the diversity contained within a group — a rough measure of the number of diversifications that the group has been through.
The International Code of Zoological Nomenclature defines rank, in the nomenclatural sense, as:
The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at the same rank, which lies between superfamily and subfamily). The ranks of the family group, the genus group, and the species group at which nominal taxa may be established are stated in Articles 10.3, 10.4, 35.1, 42.1 and 45.1.[5]There are slightly different ranks for zoology and for botany, including subdivisions such as tribe.
Source: http://en.wikipedia.org
Biological classification of Listeria
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