TAXONOMY

Taxonomic Categories Classification involves hierarchy of steps in which each step represents a rank or category. Since the category is a part of overall taxonomic arrangement, it is called the taxonomic category. All categories together constitute the taxonomic hierarchy. Each category represents a rank and is commonly termed as taxon (pl.: taxa). Species A group of individual organisms with fundamental similarities is called species. Certain distinct morphological characters distinguish one species from the other closely related species. For example; Solanum tuberosum (potato),Solanum nigrum (Black nightshade) and Solanum melongena (aubergine or eggplant) are different species from the genus Solanum. Similarly; Panthera leo (lion) andPanthera tigris (tiger) are different species from the genus Panthera. Genus  A genus is a group which is comprised of closely related speciesWe can say that genera are aggregates of closely related species. For example, potato, tomato and brinjal are three different species but all belong to the genus Solanum. Similarly; Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) belong to the genus Panthera. Family The next category, Family, has a group of related genera with still less number of similarities as compared to genus and species. Families are characterised on the basis of both vegetative and reproductive features of plant species. For example; three different genera Solanum, Petunia and Datura are placed in the family Solanaceae. Similarly; genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) belong to the family Felidae.	Order  Order is the group of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family. Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales on the basis of floral characters. The animal order, Carnivora, includes families like Felidae and Cancidae. Class The group of related orders is called class.  For example; order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog. Presence of mammary glands is one of the common characters in these orders. Phylum In the Animal Kingdom; group of closely related classes is called phylum. In the Plant Kingdom; group of closely related classes is called Division. For example; fishes, amphibians, reptiles, birds along with mammals belong to Phylum Chordata. The common features for Chordata are; presence of notochord and dorsal hollow neural system. Kingdom The group of all related phyla is called Kingdom. For example; all heterotrophs; which do not have cell wall and are eukaryotic are kept under the Animal Kingdom. All autotrophs which are eukaryotic are kept under Plant Kingdom.
Test Your Knowledge 1. Which is the lowest taxa in the classification of living beings?  2. Why do fish and mammals belong to the same Phylum?