Classification of Organisms

Grouping of organism according to similarities and differences is termed classification. When an organism is classified into various categories, a hierarchy is maintained. Accordingly, an organism belongs to Kingdom, Phylum, Class, Order, Family, Genus and Species in hierarchical order.

These are groups to which an organism belongs and which express its evolutionary relationship with other organisms. Thus, classification shows evolutionary relationships between organisms and is also termed Systematics. The science of classification or systematics is termed Taxonomy.


The scientific name of a human being is Homo sapiens. Homo sapiens means the wise hominid. Humans are classified as follows:

  • Kingdom Animalia: All animals (Multicellular, eukaryotic, heterotrophs)

  • Phylum Chordata: Animals with notochord at some stage of life.

  • Subphylum Vertebrata: Animals possessing a back bone.

  • Class Mammalia: Animals with mammary glands to provide milk for their young.

  • Order Primates: Grasping hands and feet; Share the group with monkeys and apes.

  • Family Hominidae: Group shared with primitive humans.

  • Genus Species: Homo sapiens

Three Domains of Classification

All organisms are now classified into three major domains.

  1. Archaebacteria are thermophilic or heat loving bacteria that live in high temperature vents.

  2. Eubacteria are single celled organisms without well developed nucleus.

  3. Eukarya are all other organisms with a well formed nucleus in their cell or cells. (Eu: true; Karyon: nucleus)