[Biology] Taxonomy

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INTRODUCTION

  • Taxonomy is the discipline of naming, describing and classifying organisms. This system of classifying is used for all plants, animals and microorganisms of the world.
  • The term “taxonomy” was devised by AP de Candolle, in 1813.

EXPLANATION

  • Taxonomy deals with;
    • Principles and procedures used for identification of organisms.
    • Nomenclature of organisms
    • Classification of organisms
    • The natural and phylogenetic relation among organisms.
  • Using morphological, behavioral, genetic and biochemical observations, taxonomists identify and arrange organisms into various groups.
  • Taxonomy recognizes and enumerates the components of biological diversity providing basic knowledge and supporting management.
  • Unfortunately, taxonomic knowledge is far from complete. In 250 years of research, taxonomists successfully named and classified about 1.78 million species of animals, plants and microorganisms. Yet the total number of species remains unknown and is probably up to 30 million.

CLASSICAL TAXONOMY

  • Classical taxonomy is the old method of classifying organisms, in which species is considered as a basic unit.
  • It can be described on the basis of one or few preserved specimens.
  • Classical taxonomy classifies organisms on the basis of both morphology and phylogeny.Organisms are organized on the basis of some limited features.

MODERN TAXONOMY

  • Modern taxonomy is the concept of systematics which brings out taxonomic affinity (resemblance suggesting a common descent) on the basis of evolutionary, genetic and morphological traits.
  • It is also referred as new systematics or biosystematics
  • The concept of modern taxonomy was given by Julian Huxley in 1940.
  • In this discipline of taxonomy, the classification is done on the basis of phylogenetic relationships of the organisms
  • In modern taxonomy, species is considered to be an ever-changing and dynamic entity.

WHAT IS TAXON

  • Taxon( plural Taxa), is the unit of classification in the field of taxonomy.
  • A taxon is a group of genetically similar individuals with certain features distinct from the individuals of other groups.

FOR EXAMPLE

  • The living organisms are grouped into species followed by genus, family, order, class etc.
  • Each of these categories represent a taxon.

TAXONOMICAL CATEGORIES

  • A taxonomic category represents the rank of a particular taxon
  • For example; in the case of humans, it is order primates. Here primates represent the taxon whereas order represents the taxonomic category.
  • Organisms are divided into seven major taxonomic categories.
  • This categorical distribution helps in the identification and recognition of various organisms.

KINGDOM

  • The kingdom is the highest rank in biological classification.
  • A kingdom is a group of closely associated organisms sharing a set of distinguished features.

FOR EXAMPLE

  • All plants have common features of having autotrophic mode of nutrition and the presence of cell wall made up of cellulose.
  • Hence, they are grouped into a single kingdom; Plantae.

PHYLUM/DIVISION

  • The term phylum is used for animals whereas the termed division is used for the classification of plants.
  • A phylum/division is a group of interrelated animal classes. It consists of more than one class sharing some correlated features.

FOR EXAMPLE

  • Birds and mammals are members of the same phylum; Chordata.
  • This is because of shared features i.e. the presence of notochord and dorsal hollow nerve cord.

CLASS

  • The class is a group of related orders.

FOR EXAMPLE

  • Class Mammalia consists of orders carnivora along with primata.
  • The order Carnivora includes animals like tiger, cat, and dog
  • The order Primata consists of monkeys, gorillas and gibbons.

ORDER

  • An order is a group of related families that display a few similar characters.

FOR EXAMPLE

  • plant families like Convolvulaceae, Solanaceae are included in the same order polynomials based on their floral characters.
  • Similarly, in animals, the families; Felidae and Canidae are included in the same order Carnivora.

FAMILY

  • A family is a group consisting of closely related genera.
  • They have a smaller number of similarities as compared to genus and species.
  • Families are characterized on the basis of both vegetative and reproductive features.

FOR EXAMPLE

  • in plants three different genus Solanum, petunia and the Torah are placed in the same family Solanaceae.
  • In animals, the genus Panthera including lion, tiger, leopard and genus Felisa are classified in the same family Felidae.
  • All the animals like lion, tiger, and cats have some similarities but are different from the traits found in dog hence it is placed in another family Canidae.

GENUS

  • Genus is a group of species which are alike in broad features of their organization but different in certain traits.
  • Genus consist of species which resemble one another in certain correlated characters.
  • Correlated Characters are the alike or common features which are used in limitation of a taxon above the rank of species.
  • All the species of genus are assumed to have evolved from a common ancestor.

FOR EXAMPLE

  • The plant genus Rosa, consists of more than 100 species of roses.

SPECIES

  • Species are a group of potentially inbreeding population which are reproductively isolated from other such groups.
  • It is the lowest and basic rank in taxonomic classification.
  • It consists of individuals which have fundamental similarities and can be distinguished from other similar species due to difference in morphological characters.

FOR EXAMPLE

  • Potato is species tuberosum of genus solanum (solanum tuberosum)

TAXONOMICAL HIERARCHY

Taxonomic hierarchy is the process of arranging taxonomic categories into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.

FOR EXAMPLE

The following image represents the taxonomic hierarchy of a red fox.

REFERENCES

  • Arihant’s handbook of biology. The living world. Page no: 1-6.
  • NCERT biology; textbook for class 11. The living world. Page no: 1-62.

 

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