Kingdom (biology)

Kingdom is the highest rank, after the domain, which is normally used in the biological taxonomy of all organisms. Each kingdom is split into phyla.

There are 5 to 7 kingdoms in taxonomy. Every living thing comes under one of these kingdoms and some symbionts, such as lichen, come under two. There are at least:

• Prokaryotes or Monera – the most simple living things: bacteria and archaea
• Protista – eukaryotes that are not plants, fungi, or animals
• Fungi – mushrooms, moulds and other fungi
• Plantae – all plants, such as moss, trees and grass
• Animalia – all animals, including people. See List of animal phyla
• Chromalveolata – plastids containing chlorophyll.

Overview

Linnaeus 1735	Haeckel 1866	Chatton 1925	Copeland 1938	Whittaker 1969	Woese et al. 1977	Woese et al. 1990	Cavalier-Smith 1993	Cavalier-Smith 1998
2 kingdoms	3 kingdoms	2 empires	4 kingdoms	5 kingdoms	6 kingdoms	3 domains	8 kingdoms	6 kingdoms
(not treated)	Protista	Prokaryota	Monera	Monera	Eubacteria	Bacteria	Eubacteria	Bacteria
					Archaebacteria	Archaea	Archaebacteria
		Eukaryota	Protoctista	Protista	Protista	Eucarya	Archezoa	Protozoa
							Protozoa
							Chromista	Chromista
Vegetabilia	Plantae		Plantae	Plantae	Plantae		Plantae	Plantae
				Fungi	Fungi		Fungi	Fungi
Animalia	Animalia		Animalia	Animalia	Animalia		Animalia	Animalia

The kingdom-level classification of life is still widely employed as a useful way of grouping organisms. Sometimes entries in the table, which are next to each other, do not match perfectly. For example, Haeckel placed the red algae (Haeckel's Florideae; modern Rhodophyta) and blue-green algae (Haeckel's Archephyta; modern Cyanobacteria) in his Plantae, but in modern classifications they are considered protists and bacteria respectively. However, despite these differences, the table gives a useful summary.

• There is no agreement at present on how many kingdoms there are in the Eukarya. In 2009, Andrew Roger and Alastair Simpson said this: "With the current pace of change in our understanding of the eukaryote tree of life, we should proceed with caution".

Kingdom (biology) Media

• Haeckel arbol bn.png

  Haeckel's original (1866) conception of the three kingdoms of life, including the new kingdom Protista. Notice the inclusion of the cyanobacterium Nostoc with plants.

• Eukaryote Phylogeny.png

  One hypothesis of eukaryotic relationships depicted by Alastair Simpson

Related pages

• Tree of Life