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Although [[systematist]]s today do not treat protists as a formal taxon, the term ''protist'' is currently used in two ways. The most popular contemporary definition is a [[phylogenetic]] one, that identifies a [[paraphyletic]] group: a protist is any eukaryote that is not an [[animal]], (land) [[land plant|plant]], or (true) [[fungus]]; this definition excludes many unicellular groups, like the [[Myxosporida]] (animals), the [[Microsporidia]] (fungi), many [[Chytridiomycetes]] (fungi), and [[yeast]]s (fungi). The other definition describes protists primarily by functional or biological criteria: protists are essentially those eukaryotes that are never multicellular,<ref>O'Malley MA, Simpson AGB, and Roger AJ (2013). ''[http://link.springer.com/article/10.1007%2Fs10539-012-9354-y The other eukaryotes in light of evolutionary protistology]''. ''Biology and Philosophy'' 28(2): 299–330.</ref> that either exist as independent cells, or if they occur in colonies, do not show differentiation into tissues;<ref name="Adl 05">{{cite journal |author=Adl SM, Simpson AG, Farmer MA, et al. |title=The new higher level classification of eukaryotes with emphasis on the taxonomy of protists |journal=J. Eukaryot. Microbiol. |volume=52 |issue=5 |pages=399–451 |year=2005 |pmid=16248873 |doi=10.1111/j.1550-7408.2005.00053.x}}</ref> this definition excludes the [[brown algae]], and many [[red algae|red]] and [[green algae]]. The term ''[[protozoa]]'' is used to refer to [[heterotroph]]ic species of protists that do not form filaments. These terms are not used in current taxonomy, and are retained only as convenient ways to refer to these organisms.{{citation needed|date=December 2013}}
Although [[systematist]]s today do not treat protists as a formal taxon, the term ''protist'' is currently used in two ways. The most popular contemporary definition is a [[phylogenetic]] one, that identifies a [[paraphyletic]] group: a protist is any eukaryote that is not an [[animal]], (land) [[land plant|plant]], or (true) [[fungus]]; this definition excludes many unicellular groups, like the [[Myxosporida]] (animals), the [[Microsporidia]] (fungi), many [[Chytridiomycetes]] (fungi), and [[yeast]]s (fungi). The other definition describes protists primarily by functional or biological criteria: protists are essentially those eukaryotes that are never multicellular,<ref>O'Malley MA, Simpson AGB, and Roger AJ (2013). ''[http://link.springer.com/article/10.1007%2Fs10539-012-9354-y The other eukaryotes in light of evolutionary protistology]''. ''Biology and Philosophy'' 28(2): 299–330.</ref> that either exist as independent cells, or if they occur in colonies, do not show differentiation into tissues;<ref name="Adl 05">{{cite journal |author=Adl SM, Simpson AG, Farmer MA, et al. |title=The new higher level classification of eukaryotes with emphasis on the taxonomy of protists |journal=J. Eukaryot. Microbiol. |volume=52 |issue=5 |pages=399–451 |year=2005 |pmid=16248873 |doi=10.1111/j.1550-7408.2005.00053.x}}</ref> this definition excludes the [[brown algae]], and many [[red algae|red]] and [[green algae]]. The term ''[[protozoa]]'' is used to refer to [[heterotroph]]ic species of protists that do not form filaments. These terms are not used in current taxonomy, and are retained only as convenient ways to refer to these organisms.{{citation needed|date=December 2013}}


The taxonomy of protists is still changing. Newer classifications attempt to present [[monophyly|monophyletic]] groups based on [[Morphology (biology)|morphological]] (especially [[ultrastructure|ultrastructural]]), [[biochemistry|biochemichal]] ([[chemotaxonomy]]) and [[DNA sequences]] ([[molecular phylogeny|molecular research]]) information. However, there are sometimes discordances between molecular and morphological investigations; these can be categorized as two types: (i) one morphology, multiple lineages (e.g. [[convergent evolution|morphological convergence]], [[cryptic species]]) and (ii) one lineage, multiple morphologies (e.g. [[phenotypic plasticity]], multiple [[biological life cycle|life-cycle]] stages).<ref>Lahr, D. J., Laughinghouse, H. D., Oliverio, A. M., Gao, F., & Katz, L. A. (2014). [http://www.researchgate.net/publication/265013869_How_discordant_morphological_and_molecular_evolution_among_microorganisms_can_revise_our_notions_of_biodiversity_on_Earth How discordant morphological and molecular evolution among microorganisms can revise our notions of biodiversity on Earth]. BioEssays, 36(10), 950-959.</ref>
The taxonomy of protists is still changing. Newer classifications attempt to present [[monophyly|monophyletic]] groups based on [[Morphology (biology)|morphological]] (especially [[ultrastructure|ultrastructural]]), [[biochemistry|biochemical]] ([[chemotaxonomy]]) and [[DNA sequence]] ([[molecular phylogeny|molecular research]]) information. However, there are sometimes discordances between molecular and morphological investigations; these can be categorized as two types: (i) one morphology, multiple lineages (e.g. [[convergent evolution|morphological convergence]], [[cryptic species]]) and (ii) one lineage, multiple morphologies (e.g. [[phenotypic plasticity]], multiple [[biological life cycle|life-cycle]] stages).<ref>Lahr, D. J., Laughinghouse, H. D., Oliverio, A. M., Gao, F., & Katz, L. A. (2014). [http://www.researchgate.net/publication/265013869_How_discordant_morphological_and_molecular_evolution_among_microorganisms_can_revise_our_notions_of_biodiversity_on_Earth How discordant morphological and molecular evolution among microorganisms can revise our notions of biodiversity on Earth]. BioEssays, 36(10), 950-959.</ref>


Because the protists as a whole are [[paraphyletic]], new systems often split up or abandon the kingdom, instead treating the protist groups as separate lines of eukaryotes. The recent scheme by Adl ''et al.'' (2005)<ref name="Adl 05"/> is an example that does not bother with formal ranks (phylum, class, etc.) and instead lists organisms in hierarchical lists. This is intended to make the classification more stable in the long term and easier to update. Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox, upper right.<ref name="Cavalier Smith 03">{{cite journal |author=Cavalier-Smith T, Chao EE |title=Phylogeny and classification of phylum Cercozoa (Protozoa) |journal=Protist |volume=154 |issue=3–4 |pages=341–58 |date=October 2003 |pmid=14658494 |doi=10.1078/143446103322454112 |url=}}</ref> Many are thought to be monophyletic, though there is still uncertainty. For instance, the [[excavate]]s are probably not monophyletic and the [[chromalveolate]]s are probably only monophyletic if the [[haptophyte]]s and [[cryptomonad]]s are excluded.<ref>{{cite journal | pmc = 1713255 | title = Evaluating Support for the Current Classification of Eukaryotic Diversity | author = Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz | doi = 10.1371/journal.pgen.0020220 | journal = PLoS Genet. | date = December 2006 | volume = 2 | issue = 12 | pages = e220 | pmid = 17194223}}</ref>
Because the protists as a whole are [[paraphyletic]], new systems often split up or abandon the kingdom, instead treating the protist groups as separate lines of eukaryotes. The recent scheme by Adl ''et al.'' (2005)<ref name="Adl 05"/> is an example that does not bother with formal ranks (phylum, class, etc.) and instead lists organisms in hierarchical lists. This is intended to make the classification more stable in the long term and easier to update. Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox, upper right.<ref name="Cavalier Smith 03">{{cite journal |author=Cavalier-Smith T, Chao EE |title=Phylogeny and classification of phylum Cercozoa (Protozoa) |journal=Protist |volume=154 |issue=3–4 |pages=341–58 |date=October 2003 |pmid=14658494 |doi=10.1078/143446103322454112 |url=}}</ref> Many are thought to be monophyletic, though there is still uncertainty. For instance, the [[excavate]]s are probably not monophyletic and the [[chromalveolate]]s are probably only monophyletic if the [[haptophyte]]s and [[cryptomonad]]s are excluded.<ref>{{cite journal | pmc = 1713255 | title = Evaluating Support for the Current Classification of Eukaryotic Diversity | author = Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz | doi = 10.1371/journal.pgen.0020220 | journal = PLoS Genet. | date = December 2006 | volume = 2 | issue = 12 | pages = e220 | pmid = 17194223}}</ref>

Revision as of 04:45, 24 December 2014

Protist
Temporal range: Neoproterozoic – Recent
Scientific classification
Domain:
Eukarya
Excluded groups

Many others;
classification varies

In some biological taxonomy schemes, protists (/ˈproʊt[invalid input: 'ɨ']st/) are a large and diverse group of eukaryotic microorganisms, which belong to the kingdom Protista. There have been attempts to remove the kingdom from modern taxonomy but it is still very much in use.[1][2][3] The term Protoctista is also used for these organisms by various organisations and institutions.[4][5][6] Molecular information has been used to redefine this group in modern taxonomy as diverse and often distantly related phyla. The group of protists is now considered to mean diverse phyla that are not closely related through evolution and have different life cycles, trophic levels, modes of locomotion and cellular structures.[7][8] Besides their relatively simple levels of organization, the protists do not have much in common.[9] They are unicellular, or they are multicellular without specialized tissues; this simple cellular organization distinguishes the protists from other eukaryotes, such as fungi, animals and plants, although some fungi and animals are also unicellular.

The term protista was first used by Ernst Haeckel in 1866. Protists were traditionally subdivided into several groups based on similarities to the "higher" kingdoms: the unicellular "animal-like" protozoa, the "plant-like" protophyta (mostly unicellular algae), and the "fungus-like" slime molds and water molds. These traditional subdivisions, largely based on superficial commonalities, have been replaced by classifications based on phylogenetics (evolutionary relatedness among organisms). However, the older terms are still used as informal names to describe the morphology and ecology of various protists.

Protists live in almost any environment that contains liquid water. Many protists, such as the algae, are photosynthetic and are vital primary producers in ecosystems, particularly in the ocean as part of the plankton. Other protists include pathogenic species such as the kinetoplastid Trypanosoma brucei, which causes sleeping sickness and species of the apicomplexan Plasmodium which cause malaria.

Classification

Historical classifications

Further information: wikispecies:Protista and wikispecies:Protoctista

The first groups used to classify microscopic organism were the Animalcules and the Infusoria.[10] In 1817, the German biologist Georg August Goldfuss introduced the word Protozoa to refer to organisms such as ciliates and corals.[11] This group was expanded in 1845 to include all animal-like unicellular organisms, such as foraminifera and amoebae. The formal taxonomic category Protoctista was first proposed in the early 1860s by John Hogg, who argued that the protists should include what he saw as primitive unicellular forms of both plants and animals. He defined the Protoctista as a "fourth kingdom of nature", in addition to the then-traditional kingdoms of plants, animals and minerals.[11] The kingdom of minerals was later removed from taxonomy by Ernst Haeckel, leaving plants, animals, and the protists as a “kingdom of primitive forms”.[12]

In 1938, Herbert Copeland resurrected Hogg's label, arguing that Haeckel's term protista included anucleated microbes such as bacteria, which the term "Protoctista" (literally meaning "first established beings") did not. In contrast, Copeland's term included nucleated eukaryotes such as diatoms, green algae and fungi.[13] This classification was the basis for Whittaker's later definition of Fungi, Animalia, Plantae and Protista as the four kingdoms of life.[14] The kingdom Protista was later modified to separate prokaryotes into the separate kingdom of Monera, leaving the protists as a group of eukaryotic microorganisms.[15] These five kingdoms remained the accepted classification until the development of molecular phylogenetics in the late 20th century, when it became apparent that neither protists nor monera were single groups of related organisms (they were not monophyletic groups).[16]

Some protists, sometimes called ambiregnal protists, have been considered to be both protozoa and algae or fungi (e.g., slime molds and mixotrophic algae), and names for these have been published under either or both of the ICN and the ICZN.[17][18]

Modern classifications

Phylogenetic and symbiogenetic tree of living organisms, showing the origins of eukaryotes

Although systematists today do not treat protists as a formal taxon, the term protist is currently used in two ways. The most popular contemporary definition is a phylogenetic one, that identifies a paraphyletic group: a protist is any eukaryote that is not an animal, (land) plant, or (true) fungus; this definition excludes many unicellular groups, like the Myxosporida (animals), the Microsporidia (fungi), many Chytridiomycetes (fungi), and yeasts (fungi). The other definition describes protists primarily by functional or biological criteria: protists are essentially those eukaryotes that are never multicellular,[19] that either exist as independent cells, or if they occur in colonies, do not show differentiation into tissues;[20] this definition excludes the brown algae, and many red and green algae. The term protozoa is used to refer to heterotrophic species of protists that do not form filaments. These terms are not used in current taxonomy, and are retained only as convenient ways to refer to these organisms.[citation needed]

The taxonomy of protists is still changing. Newer classifications attempt to present monophyletic groups based on morphological (especially ultrastructural), biochemical (chemotaxonomy) and DNA sequence (molecular research) information. However, there are sometimes discordances between molecular and morphological investigations; these can be categorized as two types: (i) one morphology, multiple lineages (e.g. morphological convergence, cryptic species) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity, multiple life-cycle stages).[21]

Because the protists as a whole are paraphyletic, new systems often split up or abandon the kingdom, instead treating the protist groups as separate lines of eukaryotes. The recent scheme by Adl et al. (2005)[20] is an example that does not bother with formal ranks (phylum, class, etc.) and instead lists organisms in hierarchical lists. This is intended to make the classification more stable in the long term and easier to update. Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox, upper right.[22] Many are thought to be monophyletic, though there is still uncertainty. For instance, the excavates are probably not monophyletic and the chromalveolates are probably only monophyletic if the haptophytes and cryptomonads are excluded.[23]

Metabolism

Nutrition can vary according to the type of protist. Many protists are flagellate, for example, and filter feeding can take place where the flagella find prey. Other protists can engulf bacteria and other food particles, by extending their cell membrane around them to form a food vacuole and digest them internally, in a process termed phagocytosis.

Nutritional types in protist metabolism
Nutritional type Source of energy Source of carbon Examples
 Phototrophs   Sunlight   Organic compounds or carbon fixation  Algae, Dinoflagellates or Euglena 
 Organotrophs  Organic compounds   Organic compounds   Apicomplexa, Trypanosomes or Amoebae 

Reproduction

Some protists reproduce sexually (gametes), while others reproduce asexually (binary fission).

Some species, for example Plasmodium falciparum, have extremely complex life cycles that involve multiple forms of the organism, some of which reproduce sexually and others asexually.[24] However, it is unclear how frequently sexual reproduction causes genetic exchange between different strains of Plasmodium in nature and most populations of parasitic protists may be clonal lines that rarely exchange genes with other members of their species.[25]

Eukaryotes emerged in evolution more than 1.5 billion years ago.[26] The earliest eukaryotes were likely protists. Although sexual reproduction is widespread among extant eukaryotes, it seemed unlikely until recently, that sex could be a primordial and fundamental characteristic of eukaryotes. A principal reason for this view was that sex appeared to be lacking in certain pathogenic protists whose ancestors branched off early from the eukaryotic family tree. However, several of these protists are now known to be capable of, or to recently have had the capability for, meiosis and hence sexual reproduction. For example, the common intestinal parasite Giardia lamblia was once considered to be a descendant of a protist lineage that predated the emergence of meiosis and sex. However, G. lamblia was recently found to have a core set of genes that function in meiosis and that are widely present among sexual eukaryotes.[27] These results suggested that G. lamblia is capable of meiosis and thus sexual reproduction. Furthermore, direct evidence for meiotic recombination, indicative of sex, was also found in G. lamblia.[28]

The pathogenic parasitic protists of the genus Leishmania have been shown to be capable of a sexual cycle in the invertebrate vector, likened to the meiosis undertaken in the trypanosomes.[29]

Trichomonas vaginalis, a parasitic protist, is not known to undergo meiosis, but when Malik et al.[30] tested for 29 genes that function in meiosis, they found 27 to be present, including 8 of 9 genes specific to meiosis in model eukaryotes. These findings suggest that T. vaginalis may be capable of meiosis. Since 21 of the 29 meiotic genes were also present in G. lamblia, it appears that most of these meiotic genes were likely present in a common ancestor of T. vaginalis and G. lamblia. These two species are descendants of protist lineages that are highly divergent among eukaryotes, leading Malik et al.[30] to suggest that these meiotic genes were likely present in a common ancestor of all eukaryotes.

Based on a phylogenetic analysis, Dacks and Roger proposed that facultative sex was present in the common ancestor of all eukaryotes.[31]

This view was further supported by a study of amoebae by Lahr et al.[32] Amoeba have generally been regarded as asexual protists. However these authors describe evidence that most amoeboid lineages are anciently sexual, and that the majority of asexual groups likely arose recently and independently. It should be noted that early researchers (e.g., Calkins) have interpreted phenomena related to chromidia (chromatin granules free in the cytoplasm) in amoeboid organisms as sexual reproduction.[33]

Protists generally reproduce asexually under favorable environmental conditions, but tend to reproduce sexually under stressful conditions, such as starvation or heat shock.[34] Oxidative stress, which is associated with the production of reactive oxygen species leading to DNA damage, also appears to be an important factor in the induction of sex in protists.[34]

Role as pathogens

There are some protists that are significant pathogens of animals and others that are pathogens of plants; for example there are five species of the parasitic genus Plasmodium, which cause malaria in humans; and the oomycete Phytophthora infestans, which causes late blight in potatoes.[35] A more thorough understanding of protist biology may allow these diseases to be treated more efficiently.

Recent papers have proposed the use of viruses to treat infections caused by protozoa.[36][37]

Researchers from the Agricultural Research Service are taking advantage of protists as pathogens in an effort to control red imported fire ant (Solenopsis invicta) populations in Argentina. With the help of spore-producing protists such as Kneallhazia solenopsae (this is more widely recognized as belonging to the fungus kingdom now) the red fire ant populations can be reduced by 53–100%.[38] Researchers have also found a way to infect phorid flies with the protist without harming the flies. This is important because the flies act as a vector to infect the red fire ant population with the pathogenic protist.[39]

Fossil record

Many protists have neither hard parts nor resistant spores, and their fossils are extremely rare or unknown. Examples of such groups include the apicomplexans,[40] most ciliates,[41] some green algae (the Klebsormidiales),[42] choanoflagellates,[43] oomycetes,[44] brown algae,[45] yellow-green algae,[46] excavates (e.g., euglenids).[47] Some of these have been found preserved in amber (fossilized tree resin) or under unusual conditions (e.g., Paleoleishmania, a kinetoplastid).

Others are relatively common in the fossil record,[48] as the diatoms,[49] golden algae,[50] haptophytes (coccoliths),[51] silicoflagellates, tintinnids (ciliates), dinoflagellates,[52] green algae,[53] red algae,[54] heliozoans, radiolarians,[55] foraminiferans,[56] ebriids and testate amoebae (euglyphids, arcellaceans).[57] Some are even used as paleoecological indicators to reconstruct ancient environments.

More probable eukaryote fossils begin to appear at about 1.8 billion years ago, the acritarchs, spherical fossils of likely algal protists.[58] Another possible representant of early fossil eukaryotes are the Gabonionta.

See also

References

  1. ^ Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 14601411, please use {{cite journal}} with |pmid=14601411 instead.
  2. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1371/journal.pone.0080618, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1371/journal.pone.0080618 instead.
  3. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1371/journal.pone.0077044, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1371/journal.pone.0077044 instead.
  4. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1371/journal.pone.0011916, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1371/journal.pone.0011916 instead.
  5. ^ Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 17173305, please use {{cite journal}} with |pmid=17173305 instead.
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  34. ^ a b Bernstein H, Bernstein C, Michod RE (2012). "DNA repair as the primary adaptive function of sex in bacteria and eukaryotes". Chapter 1: pp. 1–49 in DNA Repair: New Research, Sakura Kimura and Sora Shimizu (eds.). Nova Sci. Publ., Hauppauge, N.Y. ISBN 978-1-62100-808-8
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  36. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.2217/FMB.13.48, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.2217/FMB.13.48 instead.
  37. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.tim.2013.02.006, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.tim.2013.02.006 instead.
  38. ^ "ARS Parasite Collections Assist Research and Diagnoses". USDA Agricultural Research Service. January 28, 2010.
  39. ^ Durham, Sharon (January 28, 2010) ARS Parasite Collections Assist Research and Diagnoses. Ars.usda.gov. Retrieved on 2014-03-20.
  40. ^ Introduction to the Apicomplexa. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  41. ^ Fossil Record of the Ciliata. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  42. ^ Klebsormidiales. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  43. ^ Introduction to the Choanoflagellata. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  44. ^ Introduction to the Oomycota. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  45. ^ Introduction to the Phaeophyta. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  46. ^ Introduction to the Xanthophyta. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  47. ^ Introduction to the Basal Eukaryotes. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  48. ^ Why Is The Museum On The Web?. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  49. ^ Fossil Record of Diatoms. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  50. ^ Introduction to the Chrysophyta. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  51. ^ Introduction to the Prymnesiophyta. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  52. ^ Fossil Record of the Dinoflagellata. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  53. ^ Systematics of the "Green Algae", Part 1. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  54. ^ Fossil Record of the Rhodophyta. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  55. ^ Fossil Record of the Radiolaria. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  56. ^ Fossil Record of Foraminifera. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  57. ^ Introduction to the Testaceafilosea. Ucmp.berkeley.edu. Retrieved on 2014-03-20.
  58. ^ Fossil Record of the Eukaryota. Ucmp.berkeley.edu. Retrieved on 2014-03-20.

Bibliography

General

  • Haeckel, E. Das Protistenreich. Leipzig, 1878.
  • Hausmann, K., N. Hulsmann, R. Radek. Protistology. Schweizerbart'sche Verlagsbuchshandlung, Stuttgart, 2003.
  • Margulis, L., J.O. Corliss, M. Melkonian, D.J. Chapman. Handbook of Protoctista. Jones and Bartlett Publishers, Boston, 1990.
  • Margulis, L., K.V. Schwartz. Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth, 3rd ed. New York: W.H. Freeman, 1998.
  • Margulis, L., L. Olendzenski, H.I. McKhann. Illustrated Glossary of the Protoctista, 1993.
  • Margulis, L., M.J. Chapman. Kingdoms and Domains: An Illustrated Guide to the Phyla of Life on Earth. Amsterdam: Academic Press/Elsevier, 2009.
  • Schaechter, M. Eukaryotic microbes. Amsterdam, Academic Press, 2012.

Physiology, ecology and paleontology

  • Foissner, W.; D.L. Hawksworth. Protist Diversity and Geographical Distribution. Dordrecht: Springer, 2009
  • Fontaneto, D. Biogeography of Microscopic Organisms. Is Everything Small Everywhere? Cambridge University Press, Cambridge, 2011.
  • Levandowsky, M. Physiological Adaptations of Protists. In: Cell physiology sourcebook : essentials of membrane biophysics. Amsterdam; Boston: Elsevier/AP, 2012.
  • Moore, R. C., and other editors. Treatise on Invertebrate Paleontology. Protista, part B (vol. 1, Charophyta, vol. 2, Chrysomonadida, Coccolithophorida, Charophyta, Diatomacea & Pyrrhophyta), part C (Sarcodina, Chiefly “Thecamoebians” and Foraminiferida) and part D (Chiefly Radiolaria and Tintinnina). Boulder, Colorado: Geological Society of America; & Lawrence, Kansas: University of Kansas Press.

External links

Wikispecies has information related to Protista.
Wikispecies has information related to Protoctista.
Wikimedia Commons has media related to Protista.
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