| Protist Fossil range: Neoproterozoic - Recent |
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Many others; classification varies |
Protists (IPA: /ˈproʊtɨst/), Greek protiston -a meaning the (most) first of all ones, are a diverse group of organisms, comprising those eukaryotes that cannot be classified in any of the other eukaryotic kingdoms as fungi, animals, or plants. The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Robert Harding Whittaker (1920–1980 was an American Vegetation Ecologist, active in the 1950s to the 1970s Lynn Margulis (born March 5, 1938) is an American Biologist and University Professor in the Department of Geosciences In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German Year 1866 ( MDCCCLXVI) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common Chromalveolata is a Eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first The heterokonts or stramenopiles are a major line of Eukaryotes presently containing about 10500 known species The haptophytes, classed either as the Prymnesiophyta or Haptophyta are a Phylum of Algae The Chloroplasts are pigmented similarly to those of the The cryptomonads are a small group of Flagellates most of which have Chloroplasts They are common in freshwater and also occur in marine and brackish habitats The alveolates ("with cavities" are a major line of Protists There are three phyla, which are very divergent in form but are now known to be close relatives The dinoflagellates are a large group of Flagellate Protists Most are marine Plankton, but The ciliates are one of the most important groups of Protists common almost everywhere there is water — lakes ponds oceans rivers and soils with many ectosymbiotic In the classification of Eukaryotes (living organisms with a cell nucleus Cabozoa is a Taxon proposed by Cavalier-Smith. The excavates are a major assemblage of Protists often known as Excavata. 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 The Percolozoa are a group of colourless Protozoa, including many that can transform between Amoeboid, Flagellate, and encysted stages The metamonads are a large group of Flagellate protozoa Their composition is not entirely settled but they include the Retortamonads Diplomonads and The Rhizaria are a species-rich supergroup of Protists They vary considerably in form but for the most part they are Amoeboids with filose reticulose or microtubule-supported Radiolarians (also radiolaria) are Amoeboid Protozoa that produce intricate Mineral Skeletons typically with a central capsule The Foraminifera, ("Hole Bearers" or forams for short are a large group of Amoeboid Protists with reticulating Pseudopods fine The Cercozoa are a group of Protists including most Amoeboids and Flagellates that feed by means of filose pseudopods The Archaeplastida or Primoplantae are a major line of Eukaryotes comprising the land plants green and Red algae and a small The red algae (Rhodophyta ˌroʊdəˈfaɪtə roʊˈdɒfɨtə from Greek: ῥόδον (rhodon = rose + φυτόν (phyton = plant thus red plant are The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater microscopic Algae. Unikonts are members of the Unikonta a taxonomic group proposed by Thomas Cavalier-Smith. The Amoebozoa are a major group of Amoeboid protozoa including the majority that move by means of internal Cytoplasmic flow Choanozoa ( Greek: (choanos = "funnel" + (zōon = "animal" is the name of a Phylum of protists that belongs Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Plants are living Organisms belonging to the kingdom Plantae. They are usually treated as the kingdom Protista or Protoctista. In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system Protoctists (or protists) are a paraphyletic grade, rather than a natural, (monophyletic) group, and so do not have much in common besides a relatively simple organization -- either they are unicellular, or they are multicellular without highly specialized tissues. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions The term protista was coined by Ernst Haeckel in 1866. Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German Year 1866 ( MDCCCLXVI) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common
Protists were traditionally subdivided into several groups based on similarities to the "higher" kingdoms: the one-celled animal-like protozoa, the plant-like protophyta (mostly one-celled algae), and the fungus-like slime molds and water molds. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Protozoa (in Greek πρῶτον proton "first" and ζῷα zoia "animals" are unicellular Eukaryotes (singular The thallophytes are a Polyphyletic group of non-mobile Organisms traditionally described as " relatively simple Plants " or " A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Slime Mold is a broad term referring to amoeba-like organisms hence the name slime which feed on microorganisms in decaying vegetable matter hence the name Molds Oomycetes also known as Water molds (or water moulds: see spelling differences) are a group of filamentous unicellular Heterokonts physically Because these groups often overlap, they have been replaced by phylogenetic-based classifications. However, they are still useful as informal names for describing the morphology and ecology of protists. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Ecology (from Greek grc οἶκος oikos, "house(hold" and grc -λογία -logia) is the scientific study of
At one time, the non-nucleated bacteria were also considered protists under the three-kingdom system of Animalia (comprising the many-celled animals or metazoans), Plantae (which then included fungi as well as green land plants), and Protista (which included everything else, except viruses). In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions The embryophytes are the most familiar group of Plants They include Trees Flowers Ferns Mosses and various other green A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable However, most current textbooks treat bacteria (and the newly-discovered archaea) as either a separate kingdom or domain. In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms
Contents |
Obtaining nutrients
Protists obtain nutrients and digest nutrients in a complex acquirement and assimilation system. Most protists also feed on bacteria. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Protists acquire their food material through internal digestion. They extend their cell wall and cell membrane around the food material to form a food vacuole via endocytosis (usually phagocytosis; sometimes pinocytosis). A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer In general vacuole functions include Removing unwanted structural debris Isolating materials that might be harmful or a threat to the cell Containing Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole In Cellular biology, pinocytosis ("cell-drinking" "bulk-phase pinocytosis" "non-specific non-adsorptive pinocytosis" "fluid endocytosis"
Nutrition in some different types of protists is variable. In flagellates, for example, filter feeding may sometimes occur where the flagella find the prey. Filter feeders (also known as suspension feeders) are Animals that feed by straining suspended matter and food particles from water typically by passing the water In other multicellular protists, elements like nitrogen and oxygen are acquired by constant beating of the flagella. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it Protists often occur in hydrophilic conditions and thus have large amounts of oxygen within them, which is necessary for them to conduct respiration and photosynthesis to desirable levels. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.
Organization
Protozoa, the animal-like protists
Protozoa are mostly single-celled, motile protists that feed by phagocytosis, though there are numerous exceptions. Motility is a biological term which refers to the ability to move spontaneously and actively consuming energy in the process Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole They are usually only 0. 01–0. 5 mm in size, generally too small to be seen without magnification. Magnification is the process of enlarging something only in appearance not in physical size Protozoa are grouped by method of locomotion into:
| Flagellates | with long flagella | e. Flagellates are cells with one or more whip-like organelles called flagella. A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it g. , Euglena |
| Amoeboids | with transient pseudopodia | e. Euglena are a common group of Unicellular Protists, of the class Euglenoidea of the Phylum Euglenophyta. Amoeboids are Unicellular lifeforms that mainly consist of Contractile vacuoles, a nucleus, and cytoplasm as their basic structure Pseudopods or pseudopodia (from the Greek word ψευδοπόδια, ψευδός "fake false" g. , Amoeba |
| Ciliates | with multiple, short cilia | e. Amoeba (sometimes amœba or ameba, plural amoebae) is a Genus of Protozoa that moves The ciliates are one of the most important groups of Protists common almost everywhere there is water — lakes ponds oceans rivers and soils with many ectosymbiotic A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately g. , Paramecium |
| Sporozoa | non-mobile parasites; some can form spores | e. Paramecia are a group of Unicellular Ciliate Protozoa formerly known as “slipper Animalcules from their Slipper shape are commonly g. , Toxoplasma |
Algae, the plant-like protists
They include many single-celled organisms that are also considered protozoa, such as Euglena, which many believe have acquired chloroplasts through secondary endosymbiosis. Toxoplasma gondii is a species of parasitic Protozoa in the Genus Toxoplasma. Euglena are a common group of Unicellular Protists, of the class Euglenoidea of the Phylum Euglenophyta. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. An endosymbiont is any Organism that lives within the body or cells of another organism i Others are non-motile, and some (called seaweeds) are truly multicellular, including members of the following groups:
| Chlorophytes | green algae, are related to higher plants | e. Seaweed is a loose colloquial term encompassing macroscopic Multicellular, benthic marine Algae. The green algae (singular green alga) are the large group of Algae from which the Embryophytes (higher plants emerged g. , Ulva |
| Rhodophytes | red algae | e. The sea lettuces comprise the Genus Ulva, a group of edible Green algae widely distributed along the coasts of the world's Oceans The red algae (Rhodophyta ˌroʊdəˈfaɪtə roʊˈdɒfɨtə from Greek: ῥόδον (rhodon = rose + φυτόν (phyton = plant thus red plant are g. , Porphyra |
| Heterokontophytes | brown algae, diatoms, etc. Porphyra is a foliose Red algal genus of laver, comprising approximately 70 species The heterokonts or stramenopiles are a major line of Eukaryotes presently containing about 10500 known species | e. g. , Macrocystis |
The green and red algae, along with a small group called the glaucophytes, appear to be close relatives of other plants, and so some authors treat them as Plantae despite their simple organization. Macrocystis is a genus of Kelp ( Algae) This genus contains the largest of all the Phaeophyceae or Brown algae. The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater microscopic Algae. Most other types of algae, however, developed separately. They include the haptophytes, cryptomonads, dinoflagellates, euglenids, and chlorarachniophytes, all of which have also been considered protozoans. The haptophytes, classed either as the Prymnesiophyta or Haptophyta are a Phylum of Algae The Chloroplasts are pigmented similarly to those of the The cryptomonads are a small group of Flagellates most of which have Chloroplasts They are common in freshwater and also occur in marine and brackish habitats The dinoflagellates are a large group of Flagellate Protists Most are marine Plankton, but The euglenids (or euglenoids) are one of the best-known groups of Flagellates commonly found in freshwater especially when it is rich in organic materials with a Chlorarachniophytes are a small group of Algae occasionally found in tropical oceans
Note some protozoa host endosymbiotic algae, as in Paramecium bursaria or radiolarians, that provide them with energy but are not integrated into the cell. Paramecium bursaria is a species of Ciliate Protozoan that has a mutualistic symbiotic relationship with green Alga called Radiolarians (also radiolaria) are Amoeboid Protozoa that produce intricate Mineral Skeletons typically with a central capsule
Fungus-like protists
Various organisms with a protist-level organization were originally treated as fungi, because they produce sporangia. A sporangium (pl sporangia) is a Plant or fungal structure producing and containing Spores Sporangia occur in angiosperms, These include chytrids, slime molds, water molds, and Labyrinthulomycetes. Chytridiomycetes has recently been redefined to exclude the Taxa Neocallimastigomycota and Monoblepharidomycetes, which are now Slime Mold is a broad term referring to amoeba-like organisms hence the name slime which feed on microorganisms in decaying vegetable matter hence the name Molds Oomycetes also known as Water molds (or water moulds: see spelling differences) are a group of filamentous unicellular Heterokonts physically The Labyrinthulomycetes also known as Slime nets are a group of Protists that produce a network of filaments or Tubes, which serve as tracks for Of these, the chytrids are now known to be related to other fungi and are usually classified with them. The others are now placed among the heterokonts (which have cellulose rather than chitin walls) and the Amoebozoa (which do not have cell walls). The heterokonts or stramenopiles are a major line of Eukaryotes presently containing about 10500 known species Cellulose is an Organic compound with the formula, a Polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4 Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine The Amoebozoa are a major group of Amoeboid protozoa including the majority that move by means of internal Cytoplasmic flow
The term Protoctista
During the latter 20th century, the terms Protista, protist and protistan were increasingly used by biological scientists and laymen alike. Groups devoted to protistology emerged, while protozoology seemed to fade as an intellectual construct. In more recent years, however, the terms Protoctista, protoctist and protoctistan have been championed by some scholars in microbiology and micropaleontology. Microbiology (from Greek grc μῑκρος mīkros, "small" grc βίος bios, " Life " and grc -λογία Micropaleontology (also sometimes spelled as micropalaeontology) is that branch of Paleontology which studies microfossils For example, the 50-volume Treatise on Invertebrate Paleontology -- eager to fill in the gaps left by vertebrate paleontology -- has moved from its 1953 (and onwards) use of Protista to the 21st-century use of Protoctista. The Treatise on Invertebrate Paleontology (or TIP) published by the Geological Society of America and the University of Kansas Press is a definitive multi-authored Vertebrate paleontology seeks to discover the behavior reproduction and appearance of extinct spined animals through the study of their Fossilized remains So a Protist-Protoctist debate would seem to be inevitable.
The taxonomic category Protoctista was first coined by an English biologist, John Hogg, in an article entitled On the distinctions between a plant and an animal, and on a fourth kingdom of nature (1860). John Hogg (1800-1869 was a British naturalist who wrote about amphibians birds plants and protist In this article, Hogg argued that the term Protoctist should be used to include "both the Protophyta . . . and Protozoa". Therefore, he said, there should be a "fourth kingdom of nature" in addition to the then-traditional kingdoms of plants, animals and minerals. For nearly a century, however, his ideas were eclipsed by those of Haeckel, the reputed founder of protistology. Herbert F. Copeland resurrected Hogg's label almost a century later in his article, Progress report on basic classification (1947). Arguing that "Protoctista" literally meant "first established beings", Copeland complained that Haeckel's term protista included anucleated microbes such as bacteria. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Copeland's use of the term protoctista did not.
In contrast, Copeland's term included nucleated eukaryotes such as brown and red algae -- but not the green algae, which he placed with the other green plants. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The Phaeophyceae or brown algae, (singular alga is a large group of mostly marine multicellular Algae including many Seaweeds of colder The red algae (Rhodophyta ˌroʊdəˈfaɪtə roʊˈdɒfɨtə from Greek: ῥόδον (rhodon = rose + φυτόν (phyton = plant thus red plant are The green algae (singular green alga) are the large group of Algae from which the Embryophytes (higher plants emerged Plants are living Organisms belonging to the kingdom Plantae. Copeland further elaborated on his taxonomic proposal in his 1956 book, Classification of Lower Organisms (Palo Alto, California: Pacific Books). For a more recent delineation of the protoctists, see the Handbook of Protoctista (Boston: Jones & Bartlett) by Lynn Margulis, Heather I. Lynn Margulis (born March 5, 1938) is an American Biologist and University Professor in the Department of Geosciences McKhann, and Lorraine Olendzenski (1990).
Phylogenetic classifications
The taxonomy of protists is still changing. Newer classifications[1] attempt to present monophyletic groups based on ultrastructure, biochemistry, and genetics. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Ultrastructure (or ultra-structure is the detailed structure of a biological specimen such as a cell, tissue, or organ, that can be observed by Electron Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Because the protists as a whole are paraphyletic, such 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)[2] is an example that does not bother with ranks (phylum, class, etc. ).
Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox at right. 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. The excavates are a major assemblage of Protists often known as Excavata. Chromalveolata is a Eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first The haptophytes, classed either as the Prymnesiophyta or Haptophyta are a Phylum of Algae The Chloroplasts are pigmented similarly to those of the The cryptomonads are a small group of Flagellates most of which have Chloroplasts They are common in freshwater and also occur in marine and brackish habitats [3]
See also
References
- ^ Cavalier-Smith, T.; Chao, E. In taxonomy, Prasiola is a Genus of Algae, specifically of the Prasiolaceae. Professor Thomas (Tom Cavalier-Smith (born October 21 1942) FRS, FRSC, NERC Professorial Fellow is a Professor of E. Y. (2003). "Phylogeny and classification of phylum Cercozoa (Protozoa)". Protist 154 (3–4): 341–358. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Adl, S. M. ; et al. (2005). "The new higher level classification of eukaryotes with emphasis on the taxonomy of protists". Journal of Eukaryotic Microbiology 52 (5): 399–451. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz (2006 December). "Evaluating Support for the Current Classification of Eukaryotic Diversity". PLoS Genet. 2 (12): e220. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
Other references
Marguilis, L. , Corliss, J. O. , Melkonian, M. ,and Chapman, D. J. (Editors) 1990. Handbook of Protoctista. Jones and Bartlett , Boston. ISBN 0-86720-052-9
Dictionary
protist
-noun
- (microbiology) Any of the eukaryotic unicellular organisms of the kingdom Protoctista; including protozoans, slime molds and some algae.
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