[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.

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.

MODERN TAXONOMY

  • Modern taxonomy is the concept of systematic 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.

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 represents a taxon.

TAXONOMICAL CATEGORIES

  • A taxonomic category represents the rank of a particular taxon.
  • 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 Convulvaceae, 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 Carnivore.

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 consists 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 is 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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