Thomas Cavalier-Smith - AbsoluteAstronomy.com

Professor Thomas Cavalier-Smith (born October 21, 1942), FRS

Royal Society

The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

, FRSC

Royal Society of Canada

The Royal Society of Canada , may also operate under the more descriptive name RSC: The Academies of Arts, Humanities and Sciences of Canada , is the oldest association of scientists and scholars in Canada...

, NERC

Natural Environment Research Council

The Natural Environment Research Council is a British research council that supports research, training and knowledge transfer activities in the environmental sciences.-History:...

Professorial Fellow, is a Professor

Professor

A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...

of Evolutionary Biology in the Department of Zoology, at the University of Oxford

University of Oxford

The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...

.
He was presented with the International Prize for Biology

International Prize for Biology

The International Prize for Biology is an annual award for significant contributions to biology. The award was created in 1985 to recognize Emperor Hirohito of Japan's long time interest in and support of the biological sciences. The selection and award of the prize is managed by the Japan Society...

(a prize of 10 million yen) in 2004.

Life

He was educated at Norwich School

Norwich School (educational institution)

Norwich School is an independent school located in Norwich, United Kingdom. It is one of the oldest schools in the world, with a traceable history to 1096, and is a member of The Headmasters' and Headmistresses' Conference.It is a fee-paying, co-educational day school and has one of the best...

, Gonville and Caius College, Cambridge

Gonville and Caius College, Cambridge

Gonville and Caius College is a constituent college of the University of Cambridge in Cambridge, England. The college is often referred to simply as "Caius" , after its second founder, John Keys, who fashionably latinised the spelling of his name after studying in Italy.- Outline :Gonville and...

(MA) and King's College London

King's College London

King's College London is a public research university located in London, United Kingdom and a constituent college of the federal University of London. King's has a claim to being the third oldest university in England, having been founded by King George IV and the Duke of Wellington in 1829, and...

(PhD).

From 1967 to 1969, he was a guest investigator at Rockefeller University

Rockefeller University

The Rockefeller University is a private university offering postgraduate and postdoctoral education. It has a strong concentration in the biological sciences. It is also known for producing numerous Nobel laureates...

.
He taught in the biophysics department of King’s College London.
In 1989 he taught botany at the University of British Columbia

University of British Columbia

The University of British Columbia is a public research university. UBC’s two main campuses are situated in Vancouver and in Kelowna in the Okanagan Valley...

.
In 1999, he joined the University of Oxford.

He won the 2007 Frink Medal

Frink Medal

The Frink Medal for British Zoologists is awarded by the Zoological Society of London "For significant and original contributions by a professional zoologist to the development of zoology in the wider applications."- Recipients :...

of the Zoological Society of London

Zoological Society of London

The Zoological Society of London is a charity devoted to the worldwide conservation of animals and their habitats...

Classification of life

Cavalier-Smith has published extensively on the classification

Categorization

Categorization is the process in which ideas and objects are recognized, differentiated and understood. Categorization implies that objects are grouped into categories, usually for some specific purpose. Ideally, a category illuminates a relationship between the subjects and objects of knowledge...

of protists. One of his major contributions to biology was his proposal of a new kingdom

Kingdom (biology)

In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...

of life: the Chromista

Chromista

The Chromista are a eukaryotic 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...

, although the usefulness of the grouping is questionable given that it is generally agreed to be an arbitrary (polyphyletic) grouping of taxa. He also proposed that all chromista and alveolata share the same common ancestor, a claim later refuted by studies of morphological and molecular evidence by other labs. He named this new group the Chromalveolate

Chromalveolate

Chromalveolata is a eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first put forward in 1981. Chromalveolata was proposed to represent the result of a single secondary endosymbiosis between a line descending from a bikont and a red...

s. He also proposed and named many other high-rank taxa, like Opisthokont

Opisthokont

The opisthokonts or "Fungi/Metazoa group" are a broad group of eukaryotes, including both the animal and fungus kingdoms, together with the eukaryotic microorganisms that are sometimes grouped in the paraphyletic phylum Choanozoa...

a (1987), Rhizaria

Rhizaria

The Rhizaria are a species-rich supergroup of unicellular eukaryotes. This supergroup was proposed by Cavalier-Smith in 2002. They vary considerably in form, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods...

(2002), and Excavata (2002). Together with Chromalveolata, Amoebozoa

Amoebozoa

The Amoebozoa are a major group of amoeboid protozoa, including the majority that move by means ofinternal cytoplasmic flow. Their pseudopodia are characteristically blunt and finger-like,...

(he amended their description in 1998), and Archaeplastida

Archaeplastida

The Archaeplastida are a major group of eukaryotes, comprising the red and green algae and the land plants, together with a small group called the glaucophytes. The plastids of all of these organisms are surrounded by two membranes, suggesting they developed directly from endosymbiotic...

(which he called Plantae since 1981) the six form the basis of current taxonomy of eukaryote

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s. Prof. Cavalier-Smith has also published prodigiously on issues such as the origin of various cellular

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

organelles (including the nucleus

Cell nucleus

In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

, mitochondria), genome size

Genome size

Genome size is the total amount of DNA contained within one copy of a single genome. It is typically measured in terms of mass in picograms or less frequently in Daltons or as the total number of nucleotide base pairs typically in megabases . One picogram equals 978 megabases...

evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

, and endosymbiosis. Though fairly well known, many of his claims have been controversial and have not gained widespread acceptance in the scientific community

Scientific community

The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science. Objectivity is expected to be achieved by the scientific method...

to date. Most recently, he has published a paper citing the paraphyly

Paraphyly

A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...

of his bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l kingdom, the origin of Neomura

Neomura

Neomura is a clade composed of the two domains of life of Archaea and Eukaryota. The group was first proposed by Thomas Cavalier-Smith and its name means "new walls"; so called because it is thought to have evolved from Bacteria, and one of the major changes was the replacement of peptidoglycan...

from Actinobacteria

Actinobacteria

Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content. They can be terrestrial or aquatic. Actinobacteria is one of the dominant phyla of the bacteria....

and taxonomy of prokaryote

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s.

According to Palaeos

Palaeos

Palaeos.com is a web site on biology, paleontology, cladistics and geology and which covers the history of Earth. The site is well respected and has been used as a reference by professional paleontologists such as Michael J. Benton, the professor of vertebrate palaeontology in the Department of...

.com:

Prof. Cavalier-Smith of Oxford University has produced a large body of work which is well regarded. Still, he is controversial in a way that is a bit difficult to describe. The issue may be one of writing style. Cavalier-Smith has a tendency to make pronouncements where others would use declarative sentences, to use declarative sentences where others would express an opinion, and to express opinions where angels would fear to tread. In addition, he can sound arrogant, reactionary, and even perverse. On the other [hand], he has a long history of being right when everyone else was wrong. To our way of thinking, all of this is overshadowed by one incomparable virtue: the fact that he will grapple with the details. This makes for very long, very complex papers and causes all manner of dark murmuring, tearing of hair, and gnashing of teeth among those tasked with trying to explain his views of early life. See, [for example], Zrzavý (2001) [and] Patterson (1999). Nevertheless, he deals with all of the relevant facts.

The first two kingdoms of life: plants and animals

The use of the word "kingdom

Kingdom (biology)

" to describe the living world dates as far back as Linnaeus (1707–1778) who divided the natural world into three 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. Most animals are motile, meaning they can move spontaneously and...

, vegetable, and mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

. The classifications "animal kingdom" (or kingdom Animalia) and "plant kingdom" (or kingdom Plantae) remain in use by modern evolutionary biologists.

By 1910 the animal kingdom had been subdivided into twelve phyla

Phylum

In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

,
porifera,
coelenterata
Coelenterata
Coelenterata is an obsolete term encompassing two animal phyla, the Ctenophora and the Cnidaria . The name comes from the Greek "koilos" , referring to the hollow body cavity common to these two phyla...

,
platyhelminthes,
nemathelminthes,
trochhelminthes (Rotifers and Gastrotricha),
molluscoida
Molluscoida
Molluscoida was the name formerly used to denote a division of the animal kingdom which contained Brachiopods, Bryozoans, and Tunicates, the members of the three groups having been supposed to resemble the Molluscs. As it is now known that these groups have no relation to molluscs, and very little...

,
echinodermata,
annulata (Polyzoa, Phoronida, and Brachiopoda),
arthropoda,
mollusca
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...

, and
chordata.

The protozoa were originally classified as members of the animal kingdom. Now they are classified as a separate group.

Zoology

Zoology

Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

is the study of animals while botany

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

is the study of plants. While zoologists divided the animal kingdom into phyla, botanists carved the plant kingdom into "divisions". By 1940, botanists had carved the plant kingdom into five divisions:

Thallophyta (Algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, Fungi, Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, and Lichenes),
Charophyta
Charophyta
The Charophyta are a division of green algae, including the closest relatives of the embryophyte plants. In some groups, such as conjugating green algae, flagellate cells do not occur. The latter group does engage in sexual reproduction, and motility does not involve flagella, since they are...

,
Bryophyta (Heptacae
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....

and Musci),
Pteridophyta, and
Spermatophyta.

Fungi and bacteria were included within the plant division thallophyta. Today, bacteria are no longer classified as plants and fungi are known to be more closely related to animals than to plants.

The third kingdom: protists

By mid-nineteenth century, microscopic organisms

Microorganism

A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

were generally classified into four groups:

Protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

(primitive animals),
Protophyta (primitive plants),
Phytozoa (animal-like plants & plant-like animals), and
Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

(formerly regarded as plants).

In 1858, Richard Owen

Richard Owen

Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...

(1804–1892) proposed that the animal phylum Protozoa be elevated to the status of kingdom. In 1860, John Hogg

John Hogg (biologist)

John Hogg was a British naturalist who wrote about amphibians, birds, plants, and protist. In 1839 he became a member of the Royal Society....

(1800–1869) proposed that protozoa and protophyta be grouped together into a new kingdom which he called "Primigenum". According to Hogg, this new classification scheme prevented "the unnecessary trouble of contending about their supposed natures, and of uselessly trying to distinguish the Protozoa from the Protophyta". In 1866, Ernst Haeckel

Ernst Haeckel

The "European War" became known as "The Great War", and it was not until 1920, in the book "The First World War 1914-1918" by Charles à Court Repington, that the term "First World War" was used as the official name for the conflict.-Research:...

(1834–1919) proposed the name "Protista" for the Primigenum kingdom and included bacteria in this third kingdom of life.

The fourth kingdom: fungi

Fungi are more closely related to animals than to plants. By 1959, Robert Harding Whittaker

Robert Whittaker

Robert Harding Whittaker was a distinguished American plant ecologist, active in the 1950s to the 1970s.Born in Wichita, Kansas, he obtained a B.A. at Washburn Municipal College in Topeka, Kansas, and, following military service, his Ph.D...

(1920–1980) proposed that fungi, which were formerly classified as plants, be given their own kingdom. His four kingdoms of life were:

the Protista, (or unicellular organisms);
the Plantae, (or multicellular plants);
the Fungi; and
the Animalia (or multicellular animals).

Whittaker subdivided the Protista into two subkingdoms:

Monera
Monera
Monera is a superseded kingdom that contains unicellular organisms without a nucleus , such as bacteria....

(bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

) and
Eunucleata (single celled eukaryotes).

The fifth kingdom: bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

are fundamentally different from the eukaryote

Eukaryote

s (plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s, animal

Animal

s, fungi, amebas, protozoa

Protozoa

Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

, and chromista

Chromista

). Eukaryotes have cell nuclei, bacteria do not. In 1969, Robert Whittaker

Robert Whittaker

elevated the bacteria to the status of kingdom

Kingdom (biology)

. His new classification system divided the living world into five kingdoms:

plants,
animals,
protists (excluding bacteria),
fungi, and
Monera
Monera
Monera is a superseded kingdom that contains unicellular organisms without a nucleus , such as bacteria....

(the kingdom bacteria).

Note: the word "protist" is ambiguous.

Eunucleata = single celled eukaryotes

Protist

Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...

Before 1959: protist = prokaryotes + Eunucleata + sponges

From 1959 to 1969: protist = prokaryotes + Eunucleata

Since 1969: protist = Eunucleata

The three domains of life

The kingdom Monera

Monera

Monera is a superseded kingdom that contains unicellular organisms without a nucleus , such as bacteria....

can be divided into two distinct groups: eubacteria and archaebacteria. In 1977 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 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. He was also the originator of the RNA world hypothesis in 1977,...

and George E. Fox

George E. Fox

George Edward Fox is a researcher at the University of Houston and, with Carl Woese in the early 1970s, was the first scientist to classify Archaea as a separate domain of life within the three-domain system. Fox and Woese also introduced the idea of a progenote as a primordial entity in the...

proposed that eubacteria and archaebacteria both be elevated to the status of super-kingdom. In 1990, Woese further elevated the status of bacteria by dividing life into three domains

Three-domain system

The three-domain system is a biological classification introduced by Carl Woese in 1977 that divides cellular life forms into archaea, bacteria, and eukaryote domains. In particular, it emphasizes the separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria...

eubacteria (which he called "Bacteria"),
archaebacteria (which he called "Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

"), and
eukaryotes (which he called "Eukaryota").

eukaryotes = plants + chromista

Chromista

+ animals + fungi + Eunucleata

Protist

prokaryotes = Monera = eubacteria + archaebacteria

Note: the modern use of the word "bacteria" is ambiguous. It may refer either to eubacteria (as in the above phylogenetic tree) or prokaryotes (as in reference to the kingdom Monera).

The seventh kingdom: chromista

By 1981, Cavalier-Smith had divided the domain Eukaryota

Eukaryote

into nine kingdoms. By 1993, he reduced the total number of eukaryote

Eukaryote

kingdoms to six. He also classified the domains Eubacteria and Archaebacteria as kingdoms, adding up to a total of eight kingdoms of life:

Plantae,
Animalia,
Protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

,
Fungi,
Eubacteria,
Archaebacteria,
Chromista
Chromista
The Chromista are a eukaryotic 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...

, and
Archezoa
Archezoa
Archezoa was a kingdom proposed by Thomas Cavalier-Smith for eukaryotes that diverged before the origin of mitochondria. At various times, the pelobionts and entamoebids , the metamonads, and the Microsporidia were included here. These groups appear near the base of eukaryotic evolution on rRNA trees...

.

Cavalier-Smith's new classification scheme retained the plant

Plant

, animal

Animal

and fungal kingdoms from the traditional five kingdom model. It also split the kingdom Monera

Monera

Monera is a superseded kingdom that contains unicellular organisms without a nucleus , such as bacteria....

into the two groups, eubacteria and archaebacteria, as proposed by Woese

Carl Woese

and Fox

George E. Fox

. In addition it split the kingdom protists into three new kingdoms: archezoa, protozoa, and chromista.

Most chromists

Chromista

are photosynthetic. This distinguishes them from most other protists. In both plants and chromists photosynthesis takes place in chloroplasts. In plants, however, the chloroplasts are located in the cytosol

Cytosol

The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....

while in chromists the chloroplasts are located in the lumen

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

of their rough endoplasmic reticulum. This distinguishes chromists from plants.

The eighth kingdom: archezoa

Cavalier-Smith's eighth kingdom, Archezoa is now defunct. He now assigns former members of the kingdom Archezoa to the phylum Amoebozoa.

Kingdom protozoa

Cavalier-Smith referred to what remained of the protist kingdom, after he removed the kingdoms Archezoa and Chromista, as the
"kingdom Protozoa". In 1993, this kingdom contained 18 phyla as summarized in the following table:

#	Phylum	Assigned to:	Characteristics	Fate
1	Percolozoa Percolozoa The Percolozoa are a group of colourless protozoa, including many that can transform between amoeboid, flagellate, and encysted stages.-Terminology and classification:...	subkingdom Adictyozoa	lacks Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named....
2	Parabasalia	subkingdom Dictyozoa branch Parabasalia	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... lacks mitochondria
3	Euglenozoa Euglenozoa The Euglenozoa are a large group of flagellate protozoa. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. There are two main subgroups, the euglenids and kinetoplastids...	subkingdom Dictyozoa branch Bikonta infrakingdom Euglenozoa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... mostly with mitochondria with trans-splicing RNA splicing In molecular biology and genetics, splicing is a modification of an RNA after transcription, in which introns are removed and exons are joined. This is needed for the typical eukaryotic messenger RNA before it can be used to produce a correct protein through translation... of miniexons Exon An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
4	Opalozoa (flagellates)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... tubular mitochondrial cristae with cis-spliced introns predominantly ciliated, no cortical alveoli
5	Mycetozoa Mycetozoa Mycetozoa is a grouping of slime molds.-Classification:It can be divided into dictyostelid, myxogastrid, and protostelid groups.The mycetozoan groups all fit into the unikont supergroup Amoebozoa, whereas most other slime molds fit into various bikont groups .-Utility in research:Dictyostelids are... (slime molds)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... tubular mitochondrial cristae with cis-spliced introns predominantly ciliated, no cortical alveoli
6	Choanozoa Choanozoa Choanozoa is the name of a phylum of protists that belongs to the line of opisthokonts.... (choanoflagellates)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... flattened mitochondrial cristae with cis-spliced introns predominantly ciliated, no cortical alveoli
7	Dinozoa (Dinoflagellata and Protalveolata)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Alveolata	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... tubular mitochondrial cristae with cis-spliced introns with cortical alveoli	Reassigned to Miozoa in Alveolata.
8	Apicomplexa Apicomplexa The Apicomplexa are a large group of protists, most of which possess a unique organelle called apicoplast and an apical complex structure involved in penetrating a host's cell. They are unicellular, spore-forming, and exclusively parasites of animals. Motile structures such as flagella or...	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Alveolata	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... tubular mitochondrial cristae with cis-spliced introns with cortical alveoli	Reassigned to Miozoa in Alveolata.
9	Ciliophora	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Alveolata	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... tubular mitochondrial cristae with cis-spliced introns with cortical alveoli	Reassigned to Alveolata.
10	Rhizopoda (lobose and filose amoebae)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Neosarcodina	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... usually with tubular cristae with cis-spliced introns
11	Reticulosa (foraminifera Foraminifera The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net... ; reticulopodial amoebae)	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Neosarcodina	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... usually with tubular cristae with cis-spliced introns
12	Heliozoa Heliozoa Heliozoa are phagotrophs. They are roughly spherical amoeboids with many stiff, microtubule-supported projections called axopods radiating outward from the cell surface. These give them the characteristic sun-like appearance for which they are named, and are variously used for capturing food,...	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Actinopoda	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... mostly with mitochondria with cis-spliced introns has axopodia Pseudopod Pseudopods or pseudopodia are temporary projections of eukaryotic cells. Cells that possess this faculty are generally referred to as amoeboids. Pseudopodia extend and contract by the reversible assembly of actin subunits into microfilaments...
13	Radiozoa	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Actinopoda	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... mostly with mitochondria with cis-spliced introns has axopodia Pseudopod Pseudopods or pseudopodia are temporary projections of eukaryotic cells. Cells that possess this faculty are generally referred to as amoeboids. Pseudopodia extend and contract by the reversible assembly of actin subunits into microfilaments...
14	Entamoebia	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Entamoebia	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... with cis-spliced introns no mitochondria, peroxisomes, hydrogenosomes or cilia transient intranuclear centrosomes
15	Myxosporidia	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Myxozoa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia	Reclassified as animals in 1998. name="1998-08"/>
16	Haplosporidia	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Myxozoa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia	Reclassified as animals in 1998. name="1998-08"/>
17	Paramyxia Ascetosporea The Ascetosporea are a group of protists that are parasites of animals, especially marine invertebrates. There are two groups, the haplosporids and paramyxids, which are not particularly similar morphologically but consistently group together on molecular trees, which place them near the base of...	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Myxozoa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia	Reclassified as animals in 1998.
18	Mesozoa Mesozoa The Mesozoa are enigmatic, minuscule, worm-like parasites of marine invertebrates. It is still unclear as to whether they are degenerate platyhelminthes or truly-primitive, basal metazoans. Generally, these tiny, elusive creatures consist of a somatoderm of ciliated cells surrounding one or...	subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Mesozoa	has Golgi dictyosomes Golgi apparatus The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.... with cis-spliced introns tubular mitochondrial cristae multicellular with no collagenous connective tissue	Reclassified as animals in 1998.

The phylum Opalozoa was established by Cavalier-Smith in 1991.

Cavalier-Smith's six kingdom models

By 1998, Cavalier-Smith had reduced the total number of kingdoms

Kingdom (biology)

from eight to six : Animalia, Protozoa

Protozoa

, Fungi, Plantae (including red and green algae

Green algae

The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...

), Chromista

Chromista

and Bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

.

Five of Cavalier-Smith's kingdoms are classified as eukaryotes as shown in the following scheme:

Eubacteria
Neomura
Neomura
Neomura is a clade composed of the two domains of life of Archaea and Eukaryota. The group was first proposed by Thomas Cavalier-Smith and its name means "new walls"; so called because it is thought to have evolved from Bacteria, and one of the major changes was the replacement of peptidoglycan...
- Archaebacteria
- Eukaryotes
  - Kingdom Protozoa
  - Unikont
    Unikont
    Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...
    
    s (heterotrophs)
    - Kingdom Animalia
    - Kingdom Fungi
  - Bikont
    Bikont
    A Bikont is a eukaryotic cell with two flagella, as its name suggests. It is a division of eukaryotes.-Enzymes:Another shared trait of bikonts is the fusion of two genes into a single unit: the genes for thymidylate synthase and dihydrofolate reductase encode a singleprotein with two...
    
    s (primarily photosynthetic)
    - Kingdom Plantae (including red and green algae)
    - Kingdom Chromista

Eukaryotes are divided into two major groups: unikont

Unikont

Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...

s and bikont

Bikont

A Bikont is a eukaryotic cell with two flagella, as its name suggests. It is a division of eukaryotes.-Enzymes:Another shared trait of bikonts is the fusion of two genes into a single unit: the genes for thymidylate synthase and dihydrofolate reductase encode a singleprotein with two...

s. Uniciliates are cells with only one flagellum

Flagellum

A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...

and unikonts are descended from uniciliates. Unikont cells often have only one centriole

Centriole

A Centriole is a barrel-shaped cell structure found in most animal eukaryotic cells, though it is absent in higher plants and most fungi. The walls of each centriole are usually composed of nine triplets of microtubules...

as well. Biciliate cells have two flagella and bikonts are descended from biciliates. Biciliates undergo ciliary

Cilium

A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....

transformation by converting a younger anterior flagellum into a dissimilar older posterior flagellum. Animals and fungi are unikonts while plants and chromista are bikonts. Some protozoa are unikonts while others are bikonts.

The Bacteria (= prokaryotes) are subdivided into Eubacteria and Archaebacteria. According to Cavalier-Smith, eubacteria is the oldest group of terrestrial organisms still living. He classifies the groups which he believes are younger (archaebacteria and eukaryotes) as neomura

Neomura

Kingdom animalia

In 1993, Cavalier-Smith classified Myxozoa

Myxozoa

The Myxozoa are a group of parasitic animals of aquatic environments. Over 1300 species have been described and many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. The average size of a Myxosporea spore usually ranges from 10 μm to 20 μm and Malacosporea up...

as a protozoan parvkingdom. By 1998, he had reclassified it as an animal subkingdom. Myxozoa contains three phyla, Myxosporidia, Haplosporidia, and Paramyxia, which were reclassified as animals along with Myxozoa. Likewise, Cavalier-Smith reclassified the protozoan phylum Mesozoa

Mesozoa

The Mesozoa are enigmatic, minuscule, worm-like parasites of marine invertebrates. It is still unclear as to whether they are degenerate platyhelminthes or truly-primitive, basal metazoans. Generally, these tiny, elusive creatures consist of a somatoderm of ciliated cells surrounding one or...

as an animal subkingdom.

In his 1998 scheme, the animal kingdom was divided into four subkingdoms:

Radiata
Radiata
The Radiata are the radially symmetric animals of the Eumetazoa subkingdom. The term Radiata has had various meanings in the history of classification...

(phyla Porifera, Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

, Placozoa, and Ctenophora),
Myxozoa
Myxozoa
The Myxozoa are a group of parasitic animals of aquatic environments. Over 1300 species have been described and many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. The average size of a Myxosporea spore usually ranges from 10 μm to 20 μm and Malacosporea up...

,
Mesozoa
Mesozoa
The Mesozoa are enigmatic, minuscule, worm-like parasites of marine invertebrates. It is still unclear as to whether they are degenerate platyhelminthes or truly-primitive, basal metazoans. Generally, these tiny, elusive creatures consist of a somatoderm of ciliated cells surrounding one or...

, and
Bilateria
Bilateria
The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...

(all other animal phyla).

He created three new animal phyla:

Acanthognatha (rotifers, acanthocephalans, gastrotrichs, and gnathostomulids),
Brachiozoa
Brachiozoa
Brachiozoa is a grouping of animals including Brachiopoda and Phoronida....

(brachiopods and phoronids), and
Lobopoda (onychophorans and tardigrades)

and recognized a total of 23 animal phyla.

Kingdom protozoa

Under Cavalier-Smith's proposed classification system, protozoa share the following traits:

they have or are descended from organisms with mitochondria
they have or are descended from organisms with peroxisomes
they lack collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

ous connective tissue
they lack epiciliary retronemes (rigid thrust-reversing tubular ciliary hairs)
they lack two additional membranes outside their chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

envelope

Organisms that do not meet these criteria were reassigned to other kingdoms by Cavalier-Smith.

Kingdom protozoa

In 1993, Cavalier-Smith divided the kingdom Protozoa into two subkingdoms and 18 phyla

Phyla

Phyla, the plural of phylum, may refer to:* Phylum, a biological taxon between Kingdom and Class* Phylum , in linguistics, a large division of possibly related languagesPhyla, as a singular, may refer to:...

. By 2003 he used phylogenic evidence to revise the total number of proposed phyla down to 11: Amoebozoa, Choanozoa, Cercozoa, Retaria, Loukozoa, Metamonada, Euglenozoa, Percolozoa, Apusozoa, Alveolata, Ciliophora, and Miozoa.

Amoebas

Amoebas (AmE

AME

Ame, AME, or AmE may refer to* Anomalous Microwave Emission* Amé, a soft drink* Adaptive multithreaded encryption* African Methodist Episcopal Church* African Methodist Episcopal Zion Church* AME Accounting Software...

: amebas) do not have flagella and are difficult to classify as unikont

Unikont

Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...

or bikont

Bikont

based on morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

. In his 1993 classification scheme, Cavalier-Smith incorrectly classified amoebas as bikonts. Gene fusion research later revealed that the clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

Amoebozoa, was ancestrally uniciliate. In his 2003 classification scheme, Cavalier-Smith reassigned Amoebozoa

Amoebozoa

The Amoebozoa are a major group of amoeboid protozoa, including the majority that move by means ofinternal cytoplasmic flow. Their pseudopodia are characteristically blunt and finger-like,...

to the unikont clade along with animals, fungi, and the protozoan phylum Choanozoa

Choanozoa

Choanozoa is the name of a phylum of protists that belongs to the line of opisthokonts....

. Plants and all other protists where assigned to the clade Bikont by Cavalier-Smith.

Cavalier-Smith's 2003 classification scheme:

Unikont
Unikont
Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...

s
- protozoan phylum Amoebozoa
  Amoebozoa
  The Amoebozoa are a major group of amoeboid protozoa, including the majority that move by means ofinternal cytoplasmic flow. Their pseudopodia are characteristically blunt and finger-like,...
  
  (ancestrally uniciliate)
- opisthokonts
  - uniciliate protozoan phylum Choanozoa
    Choanozoa
    Choanozoa is the name of a phylum of protists that belongs to the line of opisthokonts....
  - kingdom Fungi
  - kingdom Animalia
Bikont
Bikont
A Bikont is a eukaryotic cell with two flagella, as its name suggests. It is a division of eukaryotes.-Enzymes:Another shared trait of bikonts is the fusion of two genes into a single unit: the genes for thymidylate synthase and dihydrofolate reductase encode a singleprotein with two...

s
- protozoan infrakingdom Rhizaria
  Rhizaria
  The Rhizaria are a species-rich supergroup of unicellular eukaryotes. This supergroup was proposed by Cavalier-Smith in 2002. They vary considerably in form, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods...
  - phylum Cercozoa
    Cercozoa
    The Cercozoa are a group of protists. They are sometimes described as a kingdom.-Characteristics:The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is never a true cytostome or mouth as found in...
  - phylum Retaria
    Retaria
    Retaria is a clade within the supergroup Rhizaria containing the Foraminifera and the Radiolaria....
    
    (Radiozoa and Foraminifera
    Foraminifera
    The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
    
    )
- protozoan infrakingdom Excavata
  - phylum Loukozoa
    Loukozoa
    Loukozoa is a paraphyletic taxon used in some classifications of excavate protists.The largest group within Loukozoa is the "jakobids". Loukozoa, however, also includes Malawimonas...
  - phylum Metamonada
  - phylum Euglenozoa
    Euglenozoa
    The Euglenozoa are a large group of flagellate protozoa. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. There are two main subgroups, the euglenids and kinetoplastids...
  - phylum Percolozoa
    Percolozoa
    The Percolozoa are a group of colourless protozoa, including many that can transform between amoeboid, flagellate, and encysted stages.-Terminology and classification:...
- protozoan phylum Apusozoa
  Apusozoa
  The Apusozoa are a phylum comprising several genera of flagellate protozoa. They are usually around 5-20 μm in size, and occur in soils and aquatic habitats, where they feed on bacteria...
  
  (Thecomonadea and Diphylleida)
- the chromalveolate
  Chromalveolate
  Chromalveolata is a eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first put forward in 1981. Chromalveolata was proposed to represent the result of a single secondary endosymbiosis between a line descending from a bikont and a red...
  
  clade
  - kingdom Chromista
    Chromista
    The Chromista are a eukaryotic 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...
    
    (Cryptista, Heterokonta, and Haptophyta)
  - protozoan infrakingdom Alveolata
    - phylum Ciliophora
    - phylum Miozoa (Protalveolata, Dinozoa, and Apicomplexa
      Apicomplexa
      The Apicomplexa are a large group of protists, most of which possess a unique organelle called apicoplast and an apical complex structure involved in penetrating a host's cell. They are unicellular, spore-forming, and exclusively parasites of animals. Motile structures such as flagella or...
      
      )
- kingdom Plantae (Viridaeplantae, Rhodophyta and Glaucophyta)

Cladogram

By September 2003, Cavalier-Smith's tree of life looked like this:
In the above tree, the traditional plant, animal, and fungal kingdoms, as well as Cavalier-Smith's proposed Chromista kingdom, are shown as leaves. The leaves Eubacteria and Archaebacteria together make up the Bacteria kingdom. All remaining leaves together make up the protozoa kingdom.

By 2010 new data emerged that showed that Unikonts and Bikonts, originally considered to be separate because of an apparently different organization of cilia and cytockeleton, are in reality more similar than previously thought. As a consequence, Cavalier-Smith revised the above tree and proposed to move its root to reside in between the Excavata and Euglenozoa kingdoms.

Rooting the tree of life

In 2006, Cavalier-Smith proposed that the last common ancestor to all terrestrial organisms was a non-flagellate negibacterium with two membranes.

Work (samples)

Kingdom protozoa and its 18 phyla http://scholar.google.com/scholar?cluster=14106160973358338677 http://mmbr.highwire.org/cgi/reprint/57/4/953.pdf, Microbiol Mol Biol Rev. 1993 December; 57(4): 953-994

External links

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