Tax­o­nom­ic Cat­e­gories

Clas­si­fi­ca­tion is a hier­ar­chi­cal process of orga­niz­ing liv­ing organ­isms into groups based on shared char­ac­ter­is­tics. Each lev­el in this hier­ar­chy is a tax­o­nom­ic cat­e­go­ry, and all the cat­e­gories togeth­er form the tax­o­nom­ic hier­ar­chy. Each cat­e­go­ry rep­re­sents a rank or tax­on.

Tax­o­nom­ic Hier­ar­chy

The major tax­o­nom­ic cat­e­gories, in descend­ing order, are:

• King­dom: The broad­est cat­e­go­ry (e.g., King­dom Plan­tae, King­dom Ani­malia)
• Phylum/Division: For plants, the term “divi­sion” is used.  All ani­mals with a noto­chord and dor­sal hol­low neur­al sys­tem are in Phy­lum Chor­da­ta.
• Class: Relat­ed orders are grouped into a class.  Order Pri­ma­ta (mon­keys, goril­las, gib­bons) and Order Car­nivo­ra (tigers, cats, dogs) are in Class Mam­malia.
• Order: Assem­blage of fam­i­lies with some sim­i­lar char­ac­ters.  Plant fam­i­lies Con­volvu­laceae and Solanaceae are in Order Poly­mo­ni­ales.  Fel­i­dae and Canidae are in Order Car­nivo­ra.
• Fam­i­ly: Group of relat­ed gen­era with few­er sim­i­lar­i­ties than genus or species.  Gen­era Solanum, Petu­nia, and Datu­ra are in Fam­i­ly Solanaceae.  Pan­thera (lions, tigers, leop­ards) and Felis (cats) are in Fam­i­ly Fel­i­dae.
• Genus: A group of relat­ed species with more char­ac­ters in com­mon than species of oth­er gen­era. Solanum includes tubero­sum (pota­to) and mel­on­ge­na (egg­plant). Pan­thera includes leo (lion), par­dus (leop­ard), and tigris (tiger).
• Species: The most basic unit, a group of indi­vid­u­als with fun­da­men­tal sim­i­lar­i­ties.  Mangifera indi­ca (man­go), Solanum tubero­sum (pota­to), and Pan­thera leo (lion) are exam­ples of species.

Key Points

• Species: Defined by fun­da­men­tal sim­i­lar­i­ties and dis­tinct mor­pho­log­i­cal dif­fer­ences. The sci­en­tif­ic name includes the genus and species (e.g., Homo sapi­ens).
• Genus: Gen­era are aggre­gates of close­ly relat­ed species.
• High­er Cat­e­gories: As you move up the hier­ar­chy (fam­i­ly, order, class, phylum/division, king­dom), the num­ber of com­mon char­ac­ter­is­tics decreas­es.

Exam­ples

• Species: Mangifera indi­ca, Solanum tubero­sum, Pan­thera leo, Pan­thera tigris, Solanum nigrum, Solanum mel­on­ge­na, Homo sapi­ens
• Genus: Mangifera, Solanum, Pan­thera, Homo, Felis
• Fam­i­ly: Solanaceae, Fel­i­dae, Canidae
• Order: Poly­mo­ni­ales, Car­nivo­ra
• Class: Mam­malia
• Phy­lum: Chor­da­ta
• King­dom: Plan­tae, Ani­malia

Table 1.1 From NCERT

The table pro­vides a clear illus­tra­tion of the tax­o­nom­ic hier­ar­chy using exam­ples of Man, House­fly, Man­go, and Wheat. It shows how each organ­ism is clas­si­fied from species to king­dom.

Impor­tant Con­sid­er­a­tions

• Clas­si­fi­ca­tion becomes more com­plex at high­er lev­els of the hier­ar­chy.
• Tax­o­nom­ic cat­e­gories rep­re­sent dis­tinct bio­log­i­cal enti­ties, not just mor­pho­log­i­cal aggre­gates.