Q. Of the following taxonomic categories which is the most inclusive (i.e., is the highest in the hierarchy)?
Solution:
Taxonomic hierarchy is the system of arrangement of taxonomic categories in descending order. It was introduced by Linnaeus in 1751, who initially proposed five categories (class, order, genus, species and variety). However, variety was obliterated and four new categories were introduced. Thus, the seven obligate categories in descending order are- kingdom, phylum or division, class, order, family, genus and species.
The placement of individuals or organisms in taxonomic categories is determined by their specific similar characters, dissimilarities, complexity and evolutionary relationships.
Species: It is the basic taxonomic category which consists of individuals that resemble more closely than individuals of other species. Members of a particular species have a distinct genetic makeup, can freely interbreed and are reproductively isolated from others. e.g. Potato (Solanum tuberosum), mango (Mangifera indica).
Genus: A genus may have one or many species. As per rules of binomial nomenclature, a species can be named only if it is assigned to a genus. All the species of a genus have a number of common features referred to as correlated characters.
A genus with single species is known as monotypic. e.g. Homo is monotypic with a single species of Homo sapiens.
A genus with two or more species is known as polytypic. e.g. The genus Solanum with S. tuberosum, S. melongina, S. lycopersicum.
Family: The category family is of higher rank than that of genus, and consists of one or many related genera which are more similar to one another than to genera of other families. All the genera of a family resemble one another in certain correlated characters indicating common ancestry. An animal family has a suffix - idea; and a plant family has a suffix – aeae. e.g. Family Solanaceae has genera like Solanum, Petunia, Datura and Atropa.
Order: It is an obligate category having one or more related families that possess few similar correlated characters which are less in number compared to correlated characters of genera of a family. In plants, the order ends in a suffix –ales. eg. Poales, Lamiales etc.
Class: This category is made of one or more related orders that possess certain similar correlated characters. The suffix used for plants is -phyceae, –opsida or –ae. eg. The class Dicotyledonae includes orders like Meliales, Sapindales, Poales and Lamiales.
The placement of individuals or organisms in taxonomic categories is determined by their specific similar characters, dissimilarities, complexity and evolutionary relationships.
Genus: A genus may have one or many species. As per rules of binomial nomenclature, a species can be named only if it is assigned to a genus. All the species of a genus have a number of common features referred to as correlated characters.
A genus with single species is known as monotypic. e.g. Homo is monotypic with a single species of Homo sapiens.
A genus with two or more species is known as polytypic. e.g. The genus Solanum with S. tuberosum, S. melongina, S. lycopersicum.
Order: It is an obligate category having one or more related families that possess few similar correlated characters which are less in number compared to correlated characters of genera of a family. In plants, the order ends in a suffix –ales. eg. Poales, Lamiales etc.
Class: This category is made of one or more related orders that possess certain similar correlated characters. The suffix used for plants is -phyceae, –opsida or –ae. eg. The class Dicotyledonae includes orders like Meliales, Sapindales, Poales and Lamiales.