Biology:Cavalier-Smith's system of classification
The initial version of a classification system of life by British zoologist Thomas Cavalier-Smith appeared in 1978.[1][2] This initial system continued to be modified in subsequent versions that were published until he died in 2021. As with classifications of others, such as Carl Linnaeus, Ernst Haeckel, Robert Whittaker, and Carl Woese, Cavalier-Smith's classification attempts to incorporate the latest developments in taxonomy.[3][4], Cavalier-Smith used his classifications to convey his opinions about the evolutionary relationships among various organisms, principally microbial. His classifications complemented his ideas communicated in scientific publications, talks, and diagrams. Different iterations might have a wider or narrow scope, include different groupings, provide greater or lesser detail, and place groups in different arrangements as his thinking changed. His classifications has been a major influence in the modern taxonomy, particularly of protists. [citation needed]
Cavalier-Smith has published extensively on the classification of protists. One of his major contributions to biology was his proposal of a new kingdom of life: the Chromista, 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 Chromalveolates. He also proposed and named many other high-rank taxa, like Opisthokonta (1987), Rhizaria (2002), and Excavata (2002), though he himself consistently does not include Opisthonkonta as a formal taxon in his schemes. Together with Chromalveolata, Amoebozoa (he amended their description in 1998), and Archaeplastida (which he called Plantae since 1981) the six formed the basis of the taxonomy of eukaryotes in the middle 2000s. He has also published prodigiously on issues such as the origin of various cellular organelles (including the nucleus, mitochondria), genome size evolution, and endosymbiosis. Though fairly well known, many of his claims have been controversial and have not gained widespread acceptance in the scientific community to date. Most recently, he has published a paper citing the paraphyly of his bacterial kingdom, the origin of Neomura from Actinobacteria and taxonomy of prokaryotes.
According to Palaeos.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)[5] [and] Patterson (1999).[6][7][8] Nevertheless, he deals with all of the relevant facts.[9]
Eight kingdoms model
The first two kingdoms of life: Plantae and Animalia
The use of the word "kingdom" to describe a major branch of the living world dates as far back as Linnaeus (1707–1778) who divided the natural world into three kingdoms: animal, vegetable, and mineral.[10][11] The taxa "animal kingdom" (or kingdom Animalia) and "plant kingdom" (or kingdom Plantae) remain in use by some modern evolutionary biologists. The initial targets of Cavalier-Smith's classification, the protozoa were classified as members of the animal kingdom,[12] and many algae were regarded as part of the plant kingdom. With growing awareness that the animals and plants embraced unrelated taxa, the use of the two kingdom system was rejected by specialists. It remains in use in less critical circles.
The third kingdom: Protista
right|thumb|250px| The sea anemone is an animal that resembles a plant.
By mid-nineteenth century, microscopic organisms were generally classified into four groups:
- Protozoa (primitive animals),
- Protophyta (primitive plants),
- Phytozoa (animal-like plants & plant-like animals), and
In 1858, Richard Owen (1804–1892) proposed that the animal phylum Protozoa be elevated to the status of kingdom.[13] In 1860, John Hogg (1800–1869) proposed that protozoa and protophyta be grouped together into a new kingdom which he called "Regnum Primigenum" (kingdom primitive). 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 (1834–1919) proposed the name "Protista" for the primigenial kingdom and included bacteria in this third kingdom of life.[11] [14])
The fourth kingdom: Fungi
![](/wiki/images/thumb/f/f8/Asian_mushrooms.jpg/250px-Asian_mushrooms.jpg)
By 1959, Robert Whittaker proposed that fungi, which were formerly classified as plants, be given their own kingdom. Therefore, he divided life into four kingdoms such as:
- Protista, (or unicellular organisms);
- Plantae, (or multicellular plants);
- Fungi; and
- Animalia (or multicellular animals).
Whittaker subdivided the Protista into two subkingdoms:
The fifth kingdom: Bacteria (Monera)
Bacteria are fundamentally different from the eukaryotes (plants, animals, fungi, amebas, protozoa, and chromista). Eukaryotes have cell nuclei, bacteria do not. In 1969, Whittaker elevated the bacteria to the status of kingdom. His new classification system divided the living world into five kingdoms:
- Plantae,
- Animalia,
- Protista (Eunucleata),
- Fungi, and
- Monera (the kingdom bacteria).[16]
The sixth kingdom: Archaebacteria
right|thumb|300px|Phylogenetic tree based on Woese et al. rRNA analysis in 1990 [17]
The kingdom Monera can be divided into two distinct groups: eubacteria (true bacteria) and archaebacteria (archaea). In 1977 Carl Woese and George E. Fox established that archaebacteria (methanogens in their case) were genetically different (based on their ribosomal RNA genes) from bacteria so that life could be divided into three principle lineages, namely:
- Eubacteria (all typical bacteria),
- Archaebacteria (methanogens), and
- Urkaryotes (all eukaryotes).[18]
In 1990, Woese introduced domain above kingdom by creating three-domain system such as:
- Bacteria,
- Archaea, and
- Eucarya.[19]
But Cavalier-Smith considered Archaebacteria as a kingdom.[20]
The seventh kingdom: Chromista
right |thumb|350px| The brown algae are a member of the kingdom Chromista. By 1981, Cavalier-Smith had divided all the eukaryotes into nine kingdoms.[21] In it, he created Chromista for a separate kingdom of some protists.[22]
Most chromists are photosynthetic. This distinguishes them from most other protists which lack photosynthesis. In both plants and chromists photosynthesis takes place in chloroplasts. In plants, however, the chloroplasts are located in the cytosol while in chromists the chloroplasts are located in the lumen of their rough endoplasmic reticulum. This distinguishes chromists from plants.[13]
Based on the addition of Chromista as a kingdom, he suggested that even with his nine kingdoms of eukaryotes, "the best one for general scientific use is a system of seven kingdoms",[21] which includes:
The eighth kingdom: Archezoa
In 1983, Cavalier-Smith adapted the term Archezoa, previously used by Haeckel, Perty, and for protists that lack mitochondria.[23] Initially, the taxon included the quite unrelated metamonads and microscopridia, and expanded to include other unrelated taxa such that the term referred to many different groupings of protists. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] He originally considered it as a subkingdom, but by 1989, with the establishment of Chromista as separate kingdom, he treated it as a kingdom.[20]
1983a | 1983b | 1987 | 1989 | 1990 | 1991 | 1993 | 1995 | 1996 | 1997 | 1998 | 1999 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Diplomonads | + | + | + | + | + | + | + | + | + | + | + | + |
Retortamonads | + | + | + | + | + | + | + | + | + | + | + | + |
Oxymonads | + | + | + | + | + | + | + | + | + | + | + | + |
Microspora | + | + | + | + | + | + | + | + | + | |||
Hypermastigids | + | + | + | |||||||||
Trichomonads | + | + | + | |||||||||
Mastigamoebids | + | + | + | + | + | + | ||||||
Pelomyxa | + | + | + | + | + | |||||||
Entamoeba | + | + | + | + | + | |||||||
Phreatamoeba | + | + | ||||||||||
Trimastix | + |
Archezoa is now defunct.[41] He now assigns former members of the kingdom Archezoa to the phylum Amoebozoa.[42]
Kingdom Protozoa sensu Cavalier-Smith
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.[13] The first major division relied on the basis of presence or absence of dictyosomes, although a Gogli Apparatus was subsequently demonstrated in the 'Adictyozoa'.[43]
# | Phylum | Assigned to: | Characteristics | Fate |
---|---|---|---|---|
1 | Percolozoa | subkingdom Adictyozoa | lacks Golgi dictyosomes | |
2 | Parabasalia | subkingdom Dictyozoa branch Parabasalia |
has Golgi dictyosomes lacks mitochondria |
|
3 | Euglenozoa | subkingdom Dictyozoa branch Bikonta infrakingdom Euglenozoa |
has Golgi dictyosomes mostly with mitochondria with trans-splicing of |
|
4 | Opalozoa (flagellates) | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa superphylum Opalomyxa |
has Golgi dictyosomes tubular mitochondrial cristae with cis-spliced introns predominantly ciliated, no cortical alveoli |
|
5 | Mycetozoa (slime molds) | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa superphylum Opalomyxa |
has Golgi dictyosomes tubular mitochondrial cristae with cis-spliced introns predominantly ciliated, |
|
6 | Choanozoa (choanoflagellates) | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Ciliomyxa superphylum Choanozoa |
has Golgi dictyosomes 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 superphylum Miozoa |
has Golgi dictyosomes tubular mitochondrial cristae with cis-spliced introns with cortical alveoli |
Reassigned to Miozoa in Alveolata.[44] |
8 | Apicomplexa | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Alveolata superphylum Miozoa |
has Golgi dictyosomes tubular mitochondrial cristae with cis-spliced introns with cortical alveoli |
Reassigned to Miozoa in Alveolata.[44] |
9 | Ciliophora | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Alveolata superphylum Heterokaryota |
has Golgi dictyosomes tubular mitochondrial cristae with cis-spliced introns with cortical alveoli |
Reassigned to Alveolata.[44] |
10 | Rhizopoda (lobose and filose amoebae) | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Neosarcodina |
has Golgi dictyosomes usually with tubular cristae with cis-spliced introns |
|
11 | Reticulosa (foraminifera; reticulopodial amoebae) | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Neosarcodina |
has Golgi dictyosomes usually with tubular cristae with cis-spliced introns |
|
12 | Heliozoa | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Actinopoda |
has Golgi dictyosomes mostly with mitochondria with cis-spliced introns has axopodia |
|
13 | Radiozoa | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Actinopoda |
has Golgi dictyosomes mostly with mitochondria with cis-spliced introns has axopodia |
|
14 | Entamoebia | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Entamoebia |
has Golgi dictyosomes 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 with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia |
Reclassified as animals in 1998.[45] |
16 | Haplosporidia | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Myxozoa |
has Golgi dictyosomes with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia |
Reclassified as animals in 1998.[45][clarification needed] |
17 | Paramyxia | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Myxozoa |
has Golgi dictyosomes with cis-spliced introns endoparasitic, multicellular spores, mitochondria, and no cilia |
Reclassified as animals in 1998.[45] |
18 | Mesozoa | subkingdom Dictyozoa branch Bikonta infrakingdom Neozoa parvkingdom Mesozoa |
has Golgi dictyosomes with cis-spliced introns tubular mitochondrial cristae multicellular with no collagenous connective tissue |
Reclassified as animals in 1998.[45] |
The phylum Opalozoa was established by Cavalier-Smith in 1991.[46]
Six kingdoms models
By 1998, Cavalier-Smith had reduced the total number of kingdoms from eight to six: Animalia, Protozoa, Fungi, Plantae (including red and green algae), Chromista, and Bacteria.[45]
Five of Cavalier-Smith's kingdoms are classified as eukaryotes as shown in the following scheme:
- Eubacteria
- Neomura
- Archaebacteria
- Eukaryotes
- Kingdom Protozoa
- Unikonts (heterotrophs)
- Kingdom Animalia
- Kingdom Fungi
- Bikonts (primarily photosynthetic)
- Kingdom Plantae (including red and green algae)
- Kingdom Chromista
Eukaryotes are divided into two major groups: Unikont and Bikont. Uniciliates are cells with only one flagellum and unikonts are descended from uniciliates. Unikont cells often have only one centriole as well. Biciliate cells have two flagella and bikonts are descended from biciliates. Biciliates undergo ciliary transformation by converting a younger anterior flagellum into a dissimilar older posterior flagellum. Animals and fungi are unikonts while plants and chromists 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.
The 1998 model
Kingdom Animalia
In 1993, Cavalier-Smith classified Myxozoa 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 as an animal subkingdom.
In his 1998 scheme, the animal kingdom was divided into four subkingdoms:
- Radiata (phyla Porifera, Cnidaria, Placozoa, and Ctenophora),
- Myxozoa,
- Mesozoa, and
- Bilateria (all other animal phyla).
He created five new animal phyla:
- Acanthognatha (rotifers, acanthocephalans, gastrotrichs, and gnathostomulids),
- Brachiozoa (brachiopods and phoronids),
- Lobopoda (onychophorans and tardigrades),
- Kamptozoa (Entoprocta and Symbion), and
- Nemathelminthes (Nematoda, Nematomorpha, Loricifera, Priapulida, and Kinorhyncha)
and recognized a total of 23 animal phyla, as shown here:
- Kingdom Animaia
- Subkingdom Radiata
- Infrakingdom Spongiaria
- Phylum Porifera
- Infrakingdom Coelenterata
- Phylum Cnidaria
- Phylum Ctenophora
- Infrakingdom Placozoa
- Phylum Placozoa
- Infrakingdom Spongiaria
- Subkingdom Myxozoa
- Phylum Myxosporidia
- Subkingdom Bilateria
- Branch Protostomia
- Infrakingdom Lophozoa
- Superphylum Polyzoa
- Phylum Bryozoa
- Phylum Kamptozoa (Entoprocta and Cycliophora)
- Superphylum Conchozoa
- Phylum Mollusca
- Phylum Brachiozoa sensu lato (Brachiozoa and Phoronida)
- Superphylum Sipuncula
- Phylum Sipuncula
- Superphylum Vermizoa
- Superphylum Polyzoa
- Infrakingdom Chaetognathi
- Phylum Chaetognatha
- Infrakingdom Ecdysozoa
- Superphylum Nemathelminthes
- Phylum Nemathelminthes (Nematoda and Nematomorpha; Priapozoa, Kinorhyncha and Loricifera)
- Superphylum Haemopoda
- Phylum Lobopodia (Onychophora and Tardigrada)
- Phylum Arthropoda
- Superphylum Nemathelminthes
- Infrakingdom Platyzoa
- Phylum Platyhelminthes (incl. Xenacoelomorpha)
- Phylum Acanthognatha (incl. Rotifera, Acanthocephala, Gnathostomulida, Gastrotricha)
- Infrakingdom Lophozoa
- Branch Deuterostomia
- Infrakingdom Coelomopora
- Phylum Echinodermata
- Phylum Hemichordata
- Infrakingdom Chordonia
- Phylum Urochorda
- Phylum Chordata
- Infrakingdom Coelomopora
- Branch Protostomia
- Subkingdom Mesozoa
- Subkingdom Radiata
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 collagenous connective tissue
- they lack epiciliary retronemes (rigid thrust-reversing tubular ciliary hairs)
- they lack two additional membranes outside their chloroplast envelope
Organisms that do not meet these criteria were reassigned to other kingdoms by Cavalier-Smith.
The 2003 model
Kingdom Protozoa
In 1993, Cavalier-Smith divided the kingdom Protozoa into two subkingdoms and 18 phyla.[13] 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.[44]
Unikonts and bikonts
Amoebozoa do not have flagella and are difficult to classify as unikont or bikont based on morphology. In his 1993 classification scheme, Cavalier-Smith incorrectly classified amoebas as bikonts. Gene fusion research later revealed that the clade Amoebozoa, was ancestrally uniciliate. In his 2003 classification scheme, Cavalier-Smith reassigned Amoebozoa to the unikont clade along with animals, fungi, and the protozoan phylum Choanozoa. Plants and all other protists were assigned to the clade Bikont by Cavalier-Smith.[44]
Cavalier-Smith's 2003 classification scheme:
- Unikonts
- protozoan phylum Amoebozoa (ancestrally uniciliate)
- opisthokonts
- uniciliate protozoan phylum Choanozoa
- kingdom Fungi
- kingdom Animalia
- Bikonts
- protozoan infrakingdom Rhizaria
- phylum Cercozoa
- phylum Retaria (Radiozoa and Foraminifera)
- protozoan infrakingdom Excavata
- phylum Loukozoa
- phylum Metamonada
- phylum Euglenozoa
- phylum Percolozoa
- protozoan phylum Apusozoa (Thecomonadea and Diphylleida)
- the chromalveolate clade
- kingdom Chromista (Cryptista, Heterokonta, and Haptophyta)
- protozoan infrakingdom Alveolata
- phylum Ciliophora
- phylum Miozoa (Protalveolata, Dinozoa, and Apicomplexa)
- kingdom Plantae (Viridaeplantae, Rhodophyta and Glaucophyta)
- protozoan infrakingdom Rhizaria
Cladogram of life
By September 2003, Cavalier-Smith's tree of life looked like this:[47]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
In the above tree, the traditional plant, animal, and fungal kingdoms, as well as Cavalier-Smith's proposed kingdom Chromista, are shown as leaves. The leaves Eubacteria and Archaebacteria together make up the kingdom Bacteria. All remaining leaves together make up the kingdom Protozoa.
By 2006, Cavalier-Smith's microbial tree look like this:
|
Legend: | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
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 cytoskeleton, 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.[48]
Seven kingdoms model
In 1987, Cavalier-Smith introduced a classification divided into two superkingdoms (Prokaryota and Eukaryota) and seven kingdoms, two prokaryotic kingdoms (Eubacteria and Archaebacteria) and five eukaryotic kingdoms (Protozoa, Chromista, Fungi, Plantae and Animalia).[49]
Cavalier-Smith and his collaborators revised the classification in 2015, and published it in PLOS ONE. In this scheme they reintroduced the classification with the division of prokaryotes superkingdom into two kingdoms, Bacteria (=Eubacteria) and Archaea (=Archaebacteria). This is based on the consensus in the Taxonomic Outline of Bacteria and Archaea (TOBA) and the Catalogue of Life.[50]
References
- ↑ Cavalier-Smith, T. 1978. The evolutionary origin and phylogeny of microtubules, mitotic spindles and eucaryotic flagella. BioSystems 10: 93-114.
- ↑ C. Jeffrey. 1982. Kingdoms, Codes and Classification. Kew Bulletin: 37: 403-416
- ↑ Blackwell, Will H. (2004). "Is It Kingdoms or Domains? Confusion & Solutions". The American Biology Teacher 66 (4): 268–276. doi:10.2307/4451669.
- ↑ Scamardella, Joseph M. (1999). "Not plants or animals: a brief history of the origin of Kingdoms Protozoa, Protista and Protoctista.". International Microbiology 2 (4): 207–216. PMID 10943416.
- ↑ Zrzavý, J (2001). "The interrelationships of metazoan parasites: A review of phylum-and higher-level hypotheses from recent morphological and molecular phylogenetic analyses". Folia Parasitologica 48 (2): 81–103. doi:10.14411/fp.2001.013. PMID 11437135.
- ↑ Patterson, David J. (1999). "The Diversity of Eukaryotes". The American Naturalist 154 (S4): S96–S124. doi:10.1086/303287. PMID 10527921.
- ↑ "Apusomonadida". http://www.palaeos.com/Eukarya/Units/StemMetazoa/Apusomonadida.html.
- ↑ Eukarya .
- ↑ "Origins of the Eukarya". Archived from the original on December 20, 2010. https://web.archive.org/web/20101220223738/http://palaeos.com/Eukarya/Eukarya.html. Retrieved February 9, 2009.
- ↑ Dan H. Nicolson. Animal, Vegetable or Mineral?. Proceedings of a Mini-Symposium on Biological Nomenclature in the 21st Century held at the University of Maryland on 4 November 1996. Edited by James L. Reveal
- ↑ 11.0 11.1 Scamardella, JM (1999). "Not plants or animals: A brief history of the origin of Kingdoms Protozoa, Protista and Protoctista". International Microbiology 2 (4): 207–16. PMID 10943416.
- ↑ Penny, Douglas A.; Waern, Regina (1965). Biology. An Introduction to aspects of Modern Biological Science. Vancouver Calgary Toronto Montreal: Pitman Publishing. pp. 626–40.
- ↑ 13.0 13.1 13.2 13.3 Cavalier-Smith, T (1993). "Kingdom protozoa and its 18 phyla". Microbiological Reviews 57 (4): 953–94. doi:10.1128/mmbr.57.4.953-994.1993. PMID 8302218.
- ↑ Kutschera, U. Haeckel's 1866 tree of life and the origin of eukaryotes. Nat Microbiol 1, 16114 (2016). https://doi.org/10.1038/nmicrobiol.2016.114
- ↑ Whittaker, R. H. (1959). "On the Broad Classification of Organisms". The Quarterly Review of Biology 34 (3): 210–26. doi:10.1086/402733. PMID 13844483.
- ↑ Weeks, Benjamin S.; Alcamo, I. Edward (2008). Microbes and Society (2nd ed.). Jones & Bartlett Learning. p. 32. ISBN 978-0-7637-4649-0. https://archive.org/details/microbessociety0000week. "Robert Whittaker (1969) five kingdoms."
- ↑ Woese, Carl R.; Kandler, Otto; Wheelis, Mark L. (1990). "Towards a Natural System of Organisms: Proposal for the Domains Archaea, Bacteria, and Eucarya". Proceedings of the National Academy of Sciences of the United States of America 87 (12): 4576–9. doi:10.1073/pnas.87.12.4576. PMID 2112744. Bibcode: 1990PNAS...87.4576W.
- ↑ "Phylogenetic structure of the prokaryotic domain: the primary kingdoms". Proceedings of the National Academy of Sciences of the United States of America 74 (11): 5088–90. November 1977. doi:10.1073/pnas.74.11.5088. PMID 270744. Bibcode: 1977PNAS...74.5088W.
- ↑ Cite error: Invalid
<ref>
tag; no text was provided for refs namedWoese_1990
- ↑ 20.0 20.1 Cavalier-Smith, T. (1989). "Archaebacteria and Archezoa". Nature 339 (6220): 100–101. doi:10.1038/339100a0. PMID 2497352. Bibcode: 1989Natur.339..100C.
- ↑ 21.0 21.1 Cavalier-Smith, T (1981). "Eukaryote kingdoms: Seven or nine?". Bio Systems 14 (3–4): 461–81. doi:10.1016/0303-2647(81)90050-2. PMID 7337818.
- ↑ Cavalier-Smith, T. (1986). "The kingdom Chromista : Origin and systematics". Progress in Phycological Research 4: 309–347.
- ↑ Cavalier-Smith, T. (1987). "Eukaryotes with no mitochondria". Nature 326 (6111): 332–333. doi:10.1038/326332a0. PMID 3561476. Bibcode: 1987Natur.326..332C.
- ↑ Cavalier Smith, T. 1983. A six-kingdom classification and a unified phylogeny. Endocytobiology 2:1027–1034.
- ↑ Cavalier Smith, T. 1987. Eukaryotes with no mitochondria. Nature (London) 326:332–333.
- ↑ Cavalier Smith, T. 1987 The origin of eukaryote and archaebacterial cells. Annals of the New York Academy of Sciences 503:17–54.
- ↑ Cavalier Smith, T. 1989. Archaebacteria and Archezoa. Nature (London) 339:100–101.
- ↑ Cavalier Smith, T. 1990. Microorganism megaevolution: integrating the fossil and living evidence. Revue de Micropalêontologie 33:145–154.
- ↑ Cavalier Smith, T. 1991. Archamoebae: the ancestral eukaryotes? Biosystems 25:25–38.
- ↑ Cavalier Smith, T. . The evolution of cells. pp 271–304 in S. Osawa and T. Honjo, eds. Evolution of life. Springer, Berlin.
- ↑ Cavalier Smith, T. 1992. Percolozoa and the symbiotic origin of the metakaryote cell. Endocytobiology 5:399–406.
- ↑ Cavalier Smith, T. Kingdom Protozoa and its 18 Phyla. Microbiological Reviews 57:953–994.
- ↑ Cavalier Smith, T. 1995. Zooflagellate phylogeny and classification. Cytology 37:1010–1029.
- ↑ Cavalier Smith, T. 1997. Amoeboflagellates and mitochondrial cristae in eukaryote evolution: megasystematics of the new protozoan subkingdoms Eozoa and Neozoa. Archiv für Protistenkunde 147:237–258.
- ↑ Cavalier Smith, T. 1997. Zooflagellate phylogeny and the evolution and classification of protozoa. Page 65 in Programme and abstracts, Tenth International Congress of Protozoology, Sydney.
- ↑ Cavalier Smith, T. 1998. A revised six–kingdom system of life. Biological Reviews of the Cambridge Philosophical Society 73:203–266.
- ↑ Cavalier Smith, T. 1999. Zooflagellate phylogeny and the systematics of protozoa. Biological Bulletin (Woods Hole) 196: 393–395.
- ↑ Cavalier-Smith, T.and Chao, E. 1995. The opalozoan Apusomonas is related to the common ancestor of animals, fungi and choanoflagellates. Proceedings of the Royal Society of London B, Biological Sciences 261:1–6.
- ↑ Cavalier-Smith, T.and Chao, E. 1996. Molecular diversity of the free-living archezoan Trepomonas agilis and the nature of the first eukaryote. Journal of Molecular Evolution 43:551–563.
- ↑ Patterson, D. J. 1999. The diversity of eukaryotes. American Naturalist, Supplement 65: 96-124.
- ↑ Cavalier-Smith, T.; Chao, E. E. (1996). "Molecular phylogeny of the free-living archezoan Trepomonas agilis and the nature of the first eukaryote". Journal of Molecular Evolution 43 (6): 551–62. doi:10.1007/BF02202103. PMID 8995052. Bibcode: 1996JMolE..43..551C.
- ↑ Cavalier-Smith, T. (2004). "Only six kingdoms of life". Proceedings of the Royal Society B: Biological Sciences 271 (1545): 1251–62. doi:10.1098/rspb.2004.2705. PMID 15306349.
- ↑ Herman, E. K.; Yiangou, L.; Cantoni, D. M.; Miller, C. N.; Marciano-Cabral, F.; Anthonyrajah, E.; Dacks, J. B.; Tsaousis, A. D. (2018). "Identification and characterisation of a cryptic Golgi complex in Naegleria gruberi". Journal of Cell Science 131 (7). doi:10.1242/jcs.213306. PMID 29535209.
- ↑ 44.0 44.1 44.2 44.3 44.4 Cavalier-Smith, Thomas (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348. doi:10.1078/0932-4739-00002.
- ↑ 45.0 45.1 45.2 45.3 45.4 45.5 Cavalier-Smith, T. (2007). "A revised six-kingdom system of life". Biological Reviews 73 (3): 203–66. doi:10.1111/j.1469-185X.1998.tb00030.x. PMID 9809012.
- ↑ Cavalier-Smith, Thomas (1993). "The Protozoan Phylum Opalozoa". The Journal of Eukaryotic Microbiology 40 (5): 609–15. doi:10.1111/j.1550-7408.1993.tb06117.x.
- ↑ Stechmann, Alexandra; Cavalier-Smith, Thomas (2003). "The root of the eukaryote tree pinpointed". Current Biology 13 (17): R665–6. doi:10.1016/S0960-9822(03)00602-X. PMID 12956967.
- ↑ Cavalier-Smith, Thomas (2010). "Origin of the cell nucleus, mitosis and sex: Roles of intracellular coevolution". Biology Direct 5: 7. doi:10.1186/1745-6150-5-7. PMID 20132544.
- ↑ Cavalier-Smith, Thomas (1987). "The origin of eukaryotic and archaebacterial cells". Annals of the New York Academy of Sciences 503 (1): 17–54. doi:10.1111/j.1749-6632.1987.tb40596.x. PMID 3113314. Bibcode: 1987NYASA.503...17C.
- ↑ Ruggiero, Michael A.; Gordon, Dennis P.; Orrell, Thomas M.; Bailly, Nicolas; Bourgoin, Thierry; Brusca, Richard C.; Cavalier-Smith, Thomas; Guiry, Michael D. et al. (2015). "A higher level classification of all living organisms". PLOS ONE 10 (4): e0119248. doi:10.1371/journal.pone.0119248. PMID 25923521. Bibcode: 2015PLoSO..1019248R.
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