Taxonomy

Each category is referred to as a unit of classification or rank and is commonly called taxon. A taxon is a general term for grouping in a systematic classification. A taxon refers to a group of similar and genetically related individuals having certain characters different from other groups. For example, all the insects form taxonomy as they have some common characters which are different from other groups.

Major Taxonomic Categories

There are 7 major categories, namely the kingdom, phylum, class, order, family, genus and species. The sequence can be remembered by memorizing the sentence as a pneumonic. ‘Keep sports clean family gets sick’.

(Source: wikieducator)

Category versus Taxon

The category is an abstract term that simply represents a rank or a level. Taxon represents a biological object and is assigned to a category. For example, taxon of birds is aves and the category is class. Taxonomy of sponges is peripheral and the category is phylum. On classifying an organism in a  particular taxon, we should have basic knowledge of characters of the individual group.

Species

Species is a group of actually or potentially inbreeding population reproductively isolated from other such groups. It is the lowest taxonomic characteristics. It consists of individuals which have fundamental similarities and can be distinguished from other closely related species due to distinct morphological characters.

For example, term ‘indica’ in Mangifera indica represent the specific epithet, whereas the first term Mangifera represent another higher level of taxon called genus. Each genus may have one or more than one specific epithet representing different organism for example genus Panthera can have Leo as one specific epithet representing lion and Tigris as another specific epithet representing tiger.

Genus

Genus is a group of species which are alike in broad features of their organization but different in detail. Species in a genus have common ancestry. This may be the reason for their close similarities for example genus equals has many species like Cabelas for the horse; vulgaris the ass zebra.

Family 

A family is a group of the related genus. They have still less number of similarities as compared to genus and species. Families are characterized on the basis of both vegetative and reproductive features of plant species example three different genus Solanum, petunia and the Torah at placed in the family Solanaceae.

In animals, genus Panthera including lion, tiger, leopard is put along with genus Felis in the family Felidae. All the animals like lion, tiger, and cats have some similarities but those similarities are not found in dog hence it is placed in another family Canidae.

Order

An order is a group of related families which exhibit a few similar characters. For example plant families like Convolvulaceae, Solanaceae are included in the same order polynomials based on the floral characters.  In animals family, Felidae and Canidae are included in the same order Carnivora.

Class

The class is a group of related orders. For example order Primata comprising monkeys, gorillas and gibbons are placed in Class Mammalia along with order Carnivora which includes animals like tiger, cat, and dog all having a common feature that is hair on skin and milk glands.

Phylum

A phylum is a group of related animal classes. Birds along with mammals are members of the same phylum Chordata because of the feature of presence of notochord and dorsal hollow nerve cord. In plants Classes with a few similar characters are arranged in a higher category of Division.

Kingdom

The kingdom is the highest category in biological classification. It is a group of closely related organisms. Example all plants have common features of the autotrophic mode of nutrition and presence of cell wall made up of cellulose. Hence they belong to the kingdom Plantae. Taxonomists have also developed subcategories in this higher key for more sound and scientific placement of various taxa.