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;

1. Principles and procedures used for identification of organisms.
2. Nomenclature of organisms
3. Classification of organisms
4. 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 Charactersare 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.