Kingdom (Biology)

Kingdom is one of the major ranks in the taxonomic classification of living things, which is the system for organizing life based on shared characteristics and evolutionary relationships. Kingdom ranks below the domain (or superkingdom) and above the phylum (or division in plants).

Each kingdom groups together a large array of organisms that share fundamental features, such as cell structure, how they obtain food, and how they grow. The number of kingdoms and their names are not uniformly agreed upon by all classification systems; they have changed as DNA sequencing technology has advanced.

History of the concept

In the early modern period, living things were divided into only two kingdoms: plants and animals. Carl Linnaeus used this two-part classification in the 18th century. As the microscope improved and organisms were discovered that did not fit neatly into either category—such as bacteria, fungi, and single-celled organisms—a need arose for additional divisions.

By the 20th century, five-kingdom systems had become standard: Monera (bacteria), Protista, Fungi, Plantae, and Animalia. Later, after comparing DNA sequences, a higher rank called the domain was proposed, dividing life into Bacteria, Archaea, and Eukaryota.

Major kingdoms

The most commonly recognized kingdoms include: Animalia, encompassing many-celled organisms with many cells that obtain food by consuming other organisms; Plantae, which produce food using sunlight through photosynthesis; Fungi, whose members derive nutrition from matter around them; and various single-celled groups often called Protista, though the latter does not form a cohesive group with a common ancestor.