domainkingdomphylum

Domainkingdomphylum refers to three hierarchical levels used in biological classification: domain, kingdom, and phylum. In modern taxonomy, the domain is the highest rank, followed by kingdom, then phylum, and continuing through class, order, family, genus, and species. The three-domain system, proposed by Carl Woese and colleagues, divides life into Bacteria, Archaea, and Eukarya. This framework reflects major evolutionary lineages based largely on genetic differences, especially ribosomal RNA sequences.

Within each domain, organisms are organized into kingdoms (though the number and names of kingdoms vary by system). For example, in the domain Eukarya, traditional schemes include kingdoms such as Animalia, Plantae, Fungi, and various groups of protists. Within each kingdom are numerous phyla, which group organisms by broad structural and developmental characteristics. In animals, well-known phyla include Chordata (animals with a notochord) and Arthropoda (insects, spiders, crustaceans). In plants, classifications often use divisions or phyla such as Bryophyta (mosses) and Magnoliophyta (flowering plants), depending on the taxonomic system used.

Phylum represents a mid-level category that captures major body plans and organizational traits within a kingdom. The exact composition of kingdoms and phyla can change with new data, especially from molecular phylogenetics, which can reassign organisms to different groups or redefine boundaries. The terms domain, kingdom, and phylum therefore reflect a hierarchical approach to organizing biodiversity, while remaining subject to revision as scientific understanding advances.