Kingdom (biology)

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Kingdom (biology)

In biological

Biology

Biology is a branch of the natural sciences concerned with the study of living organisms and their interaction with each other and their environment ....
taxonomy

Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
, kingdom or regnum is a taxonomic rank

Taxonomic rank

Taxonomic rank, taxonomic category, rank, or category is an abstract term used in the scientific classification, or taxonomy, of organisms....
in either (historically) the highest rank, or (in the new three-domain system

Three-domain system

Domain (biology)

In Biology taxonomy, a domain is the highest taxonomic rank of organisms, higher than a Kingdom . According to the three-domain system of Carl Woese, introduced in 1990, the Tree of life consists of three domains: Archaea, Bacteria and Eukaryota....
. Each kingdom is divided into smaller groups called phyla

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
(or in some contexts these are called "divisions"). Currently, many textbooks from the United States use a system of six kingdoms (Animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
ia, Plantae, Fungi, Protista, Archaea

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
, Bacteria

Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
) while British and Australian textbooks may describe five kingdoms (Animalia, Plantae, Fungi, Protista, and Prokaryota or Monera

Monera

Monera are bacteria and other mostly tiny, single-celled organisms whose genetic material is loose in the cell. The genetic material of plants, animals, and other eukaryotes , on the other hand, is held in the cell's nucleus....
).

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Encyclopedia

In biological

Biology

Biology is a branch of the natural sciences concerned with the study of living organisms and their interaction with each other and their environment ....
taxonomy

Taxonomy

Taxonomic rank

Three-domain system

Domain (biology)

Phylum

Animal

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
, Bacteria

Bacteria

Monera

Life

Life is a characteristic of organisms that exhibit certain biological processes such as chemical reactions or other events that results in a transformation....
, domain

Domain (biology)

Kingdom (biology)

In Biology taxonomy, kingdom or regnum is a taxonomic rank in either the highest rank, or the Rank below domain . Each kingdom is divided into smaller groups called Phylum ....
, phylum

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
, class

Class (biology)

A class is the taxonomic rank in the biological classification of organisms in biology below phylum and above Order .The orders of taxonomy are life, Domain , kingdom , phylum, class , order , family , genus, and species....
, order

Order (biology)

In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
, family

Family (biology)

In biological classification, family is a taxonomic rank. Exact details of formal nomenclature depend on the Nomenclature Codes which applies....
, genus

Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
, and species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
.

Carolus Linnaeus

Carolus Linnaeus

Carl Linnaeus was a Sweden botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern alpha taxonomy, and is also considered one of the fathers of modern ecology....
distinguished two kingdoms of living things: Animalia for animal

Animal

Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s (Linnaeus also treated mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s, placing them in a third kingdom, Mineralia). Linnaeus divided each kingdom into classes, later grouped into phyla

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
for animals and divisions for plants. It gradually became apparent how important the prokaryote/eukaryote distinction is, and Stanier and van Niel popularized Edouard Chatton

Edouard Chatton

Edouard Chatton , was a French biologist who first distinguished between the eukaryotic and prokaryotic systems of cellular organisation, and coined the terms themselves in his 1925 paper, Pansporella perplex: Reflections on the Biology and Phylogeny of the Protozoa....
's proposal in the 1960s.

Five kingdoms

Robert Whittaker

Robert Harding Whittaker was an United States vegetation ecologist, active in the 1950s to the 1970s.Born in Wichita, Kansas, he obtained a B.A....
recognized an additional kingdom for the Fungi

Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
. The resulting five-kingdom system, proposed in 1969, has become a popular standard and with some refinement is still used in many works, or forms the basis for newer multi-kingdom systems. It is based mainly on differences in nutrition

Nutrition

Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with good nutrition....
; his Plantae were mostly multicellular autotroph

Autotroph

An autotroph is an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions....
s, his Animalia multicellular heterotroph

Heterotroph

A heterotroph is an organism that organic compound substrates to get its Energy#Chemical energy for its life cycle. This contrasts with autotrophs such as plants which are able to directly use sources of energy such as light to produce organic substrates from inorganic carbon dioxide....
s, and his Fungi multicellular saprotrophs. The remaining two kingdoms, Protista and Monera, included unicellular and simple cellular colonies.

Six kingdoms

In the years around 1980, there was an emphasis on phylogeny and redefining the kingdoms to be monophyletic groups, groups made up of relatively closely related organisms. The Animalia, Plantae, and Fungi were generally reduced to core groups of closely related forms, and the others placed into the Protista. Based on RNA

RNA

Ribonucleic acid is a type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nucleobase, a ribose sugar, and a phosphate....
studies, Carl Woese

Carl Woese

Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of Svedberg ribosome RNA, a technique pioneered by Woese and which is now standard practice....
divided the prokaryotes (Kingdom Monera) into two kingdoms, called Eubacteria and Archaebacteria

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
. Carl Woese attempted to establish a Three Primary Kingdom (or Urkingdom) system in which Plants, Animals, Protista, and Fungi were lumped into one primary kingdom of all eukaryotes. The Eubacteria and Archaebacteria made up the other two urkingdoms. The initial use of "six Kingdom systems" represents a blending of the classic Five Kingdom system and Woese's Three Kingdom system. Such six Kingdom systems have become standard in many works.

A variety of new eukaryotic kingdoms were also proposed, but most were quickly invalidated, ranked down to phyla or classes, or abandoned. The only one which is still in common use is the kingdom Chromista

Chromista

Thomas Cavalier-Smith

Professor Thomas Cavalier-Smith , Royal Society, Royal Society of Canada, Natural Environment Research Council Professorial Fellow, is a Professor of Evolutionary Biology in the Department of Zoology, at the University of Oxford....
, including organisms such as kelp

Kelp

Kelp are large seaweed plants , belonging to the brown algae and classified in the order Laminariales. There are about 30 different genus. Some species can be very long and form kelp forests....
, diatom

Diatom

Diatoms are a major group of eukaryote algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as Colony in the shape of filaments or ribbons , fans , zigzags , or stellate colonies ....
s, and water mould

Water mould

Oomycota also known as Water molds are a group of filamentous, unicellular Heterokonts, physically resembling fungus. They are microscopic, absorptive organisms that reproduce both sexually and asexually and are composed of mycelia, or a tube-like vegetative body ....
s. Thus the eukaryotes are divided into three primarily heterotrophic groups, the Animalia, Fungi, and Protozoa, and two primarily photosynthetic groups, the Plantae (including red and green algae) and Chromista. However, it has not become widely used because of uncertainty over the monophyly of the latter two kingdoms.

Woese stresses genetic similarity over outward appearances and behaviour, relying on comparisons of ribosomal RNA genes at the molecular level to sort out classification categories. A plant does not look like an animal, but at the cellular level, both groups are eukaryotes, having similar subcellular organization, including cell nuclei, which the Eubacteria and Archaebacteria do not have. More importantly, plants, animals, fungi, and protists are more similar to each other in their genetic makeup at the molecular level, based on RNA studies, than they are to either the Eubacteria or Archaebacteria. Woese also found that all of the eukaryotes, lumped together as one group, are more closely related, genetically, to the Archaebacteria than they are to the Eubacteria. This means that the Eubacteria and Archaebacteria are separate groups even when compared to the eukaryotes. So, Woese established the Three-domain system

Three-domain system

The three-domain system is a biological classification introduced by Carl Woese in 1990 that divides cellular life forms into archaea, bacteria, and eukaryote domain s....
, clarifying that all the Eukaryotes are more closely genetically related compared to their genetic relationship to either the bacteria or the archaebacteria, without having to replace the "six kingdom systems" with a three kingdom system. The Three Domain system is a "six kingdom system" that unites the eukaryotic kingdoms into the Eukarya Domain based on their relative genetic similarity when compared to the Bacteria Domain and the Archaea Domain. Woese also recognized that the Protista Kingdom is not a monophyletic group and might be further divided at the level of Kingdom. Others have divided the Protista Kingdom into the Protozoa and the Chromista, for instance.

Recent advances

Classification is an ongoing area of research and discussion. As new findings and technologies become available they allow the refinement of the model. For example, gene sequencing techniques allow the comparison of the genome of different groups (Phylogenomics

Phylogenomics

Phylogenomics can be regarded as the intersection between the fields of evolution and genomics . The term has been used in multiple ways to refer to some type of analysis involving genome data and evolutionary reconstructions, especially phylogenetics....
). A study published in 2007 by Fabien Burki, et al proposes four high level groups of eukaryotes based on phylogenomics research.

Plantae (green and red algae, and plants)
Opisthokont
Opisthokont

The opisthokonts are a broad group of eukaryotes, including both the animal and fungus kingdom , together with the phyla Choanozoa and Mesomycetozoa of the protist "kingdom"....
s (amoebas, fungi, and animals)
Excavata (free-living and parasitic protist
Protist

Protists ; eukaryote microorganisms. Historically, protists were treated as the kingdom Protista but this group is no longer recognized in modern taxonomy....
s)
SAR (acronym for Stramenopiles, Alveolate
Alveolate

The alveolates are a major line of protists....
s, and Rhizaria
Rhizaria

The Rhizaria are a species-rich supergroup of protists. They vary considerably in form, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods....
–the names of some of its members. Burki found that the previously split groups Rhizaria and Chromalveolate
Chromalveolate

Chromalveolata is a eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first proposed in 1981....
s were more similar in 123 common genes than once thought.)

Recent phylogenetic studies suggest there are anywhere from 18 to over 30 different kingdoms that have been discovered.

Summary

Linnaeus (1735) 2 kingdoms	Haeckel Ernst Haeckel 'Ernst Heinrich Philipp August Haeckel' ,also written 'von Haeckel', was an eminent Germany biologist, natural history, philosopher, physician, professor and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including phylum, ph... (1866) 3 kingdoms	Chatton Edouard Chatton Edouard Chatton , was a French biologist who first distinguished between the eukaryotic and prokaryotic systems of cellular organisation, and coined the terms themselves in his 1925 paper, Pansporella perplex: Reflections on the Biology and Phylogeny of the Protozoa.... (1925) 2 groups	Copeland Herbert Copeland Herbert Faulkner Copeland was an American biologist who contributed to the theory of biological kingdom s. His father was Edwin Copeland. He was responsible for the fourth kingdom, Monera.... (1938) 4 kingdoms	Whittaker Robert Whittaker Robert Harding Whittaker was an United States vegetation ecologist, active in the 1950s to the 1970s.Born in Wichita, Kansas, he obtained a B.A.... (1969) 5 kingdoms	Woese Carl Woese Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of Svedberg ribosome RNA, a technique pioneered by Woese and which is now standard practice.... (1977,1990) 3 domains
Animalia	Animalia	Eukaryote Eukaryote Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....	Animalia	Animalia	Eukarya
Vegetabilia	Plantae		Plantae	Plantae
			Protoctista	Fungi
				Protista
(not treated)	Protista			Protista
		Procaryote	Monera Monera Monera are bacteria and other mostly tiny, single-celled organisms whose genetic material is loose in the cell. The genetic material of plants, animals, and other eukaryotes , on the other hand, is held in the cell's nucleus....	Monera Monera Monera are bacteria and other mostly tiny, single-celled organisms whose genetic material is loose in the cell. The genetic material of plants, animals, and other eukaryotes , on the other hand, is held in the cell's nucleus....	Archaea Archaea The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
		Procaryote			Bacteria Bacteria The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....

Note that the equivalences in this table are not perfect. e.g. Haeckell placed the red algae

Red algae

The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000?6,000 species of mostly multicellular, ocean algae, including many notable seaweeds....
(Haeckell's Florideae; modern Florideophyceae

Florideophyceae

Florideophyceae was a class of red algae. It is now merged with the Bangiaceae into the Rhodophyceae.They were once thought to be the only algae to bear pit connections, but these have since been found in the filamentous stage of the Bangiacae....
) and blue-green algae (Haeckell's Archephyta; modern Cyanobacteria

Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
) in his Plantae.

In 1998, Cavalier-Smith proposed that Protista should be divided into 2 new kingdoms: Chromista

Chromista

The Chromista are a eukaryote supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them....
the phylogenetic group of golden-brown algae that includes those algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them, and Protozoa

Protozoa

Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....
, the kingdom of protozoans. This proposal has not been widely-adopted, although the question of the relationships between different domains of life remains controversial.

Empires	Kingdoms
Prokaryota	Bacteria Bacteria The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
Eukaryota	Animalia	Plantae	Fungi	Chromista Chromista The Chromista are a eukaryote supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them....	Protozoa Protozoa Protozoan are microorganisms classified as unicellular eukaryotes. While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate....

Kingdom (biology)

Five kingdoms

Six kingdoms

Recent advances

Summary

See also

External links