What is the cell wall made of?
A protist is an animal, plant, or fungus that does not have a cell nucleus.Protists do not form a natural group, or clade, because they don't share a common ancestor.The grouping is used for convenience because some protists are more closely related to animals, plants, or fungi than others.Protistology is the study of protists.[4]
The Protoctista kingdom was first proposed by John Hogg in 1860 as the kingdom that was separate from animals and plants.With time these would be removed to a fourth kingdom.The fifth kingdom Fungi was established in the popular five-kingdom scheme proposed by Robert Whittaker in 1969.The term protist is only used for small organisms in the five-kingdom system of Lynn Margulis.Some people use the term protist interchangeably with Margulis's protoctist, to encompass both single-celled and multicellular eukaryotes, including those that form specialized tissues but do not fit into any of the other traditional kingdoms.10
Protists do not have much in common.The term "protists" is no longer used because they do not have an exclusive common ancestor and have different life cycles.Examples of protists include amoebas, choanaflagellates, ciliates, diatoms, and Giardia.These examples are unicellular, even though oomycetes and slime molds can aggregate.
There are no equivalents to the taxa Protista or Protoctista, as both terms refer to a paraphyletic group that spans the entire tree of life.The contents of Protista are mostly distributed among various super groups."Protista", " Protoctista," and "protozoa" are no longer relevant.The term "protist" is still used informally as a catch-all term for organisms that aren't within other traditional kingdoms.It is possible to use the word "protist pathogen" to mean any disease-causing organisms that are not plant.[15]
In 1866, the term protista was first used.The protists were divided into several groups based on similarities to the higher kingdoms.
The names of some protists have been published under both the ICN and the ICZN.The kingdom Protista was adopted because of conflicts such as the dual-classification of Euglenids and Dinobryons, which are mixotrophic.
The traditional subdivisions have been replaced by classifications based on evolutionary relatedness among organisms.The former members of this group have been redistributed into other groups using modern taxonomy.The water mold is now considered to be related to Brown algae and Diatoms, and the Amoebozoa itself includes only a subset of the "Amoeba" group.
The older terms are still used to describe the ecology of protists.Heterotrophic species of protists that do not form filaments are referred to as protozoa.
The pioneers in the study of the protists were mostly ignored by Linnaeus.The Animalcules and the Infusoria were the first groups to classify organisms.August Goldfuss introduced the word Protozoa to refer to organisms such as ciliates and corals.After the cell theory of Schwann and Schleiden, Carl von Siebold modified the group to include only animal-like unicellular organisms.The formal category Protoctista was first proposed in the early 1860s by John Hogg, who argued that the protists should include primitive unicellular forms of both plants and animals.The Protoctista was defined as a fourth kingdom of nature in addition to the traditional kingdoms of plants, animals and minerals.The protists and plants were left out of the kingdom of minerals in the 19th century.[25][26]
The term "protoctista" did not include anucleated microbes, which was argued to be the case by Herbert Copeland.Nucleated organisms such as diatoms, green algae and fungi were included in Copeland's term.Whittaker defined the four kingdoms of life as Fungi, Animalia, Plantae and Protista.The kingdom Protista was changed to separate prokaryotes into a separate kingdom called Monera.The classification of these five kingdoms was changed in the late 20th century when it became apparent that neither protists nor monera were single groups of related organisms.[28]
The term "protist" is used for convenience in two ways, but systematists do not treat Protista as a formal taxon.The most popular definition of a paraphyletic group is a protist, which excludes many unicellular organisms.Some systematists?Use Protista as a formal taxon if you want to judge paraphyletic taxa.There is a citation needed.
Protists are essentially those cells that are never multicellular, or if they occur in colonies, do not show differentiation into tissues, which is what the other definition describes.
The protists are still changing.The new classifications try to present monophyletic groups based on the information they have.There are two types of investigations: one and the other.There are two types of convergence, cryptic species and multiple morphologies.There are multiple life-cycle stages.[41]
Because the protists as a whole are paraphyletic, new systems often split up or abandon the kingdom.The recent scheme by Adl et al.The 2005[33] does not recognize formal ranks.Groups are treated as clades of related organisms.It is intended to make the classification more stable and easier to update.Some of the main groups of protists are listed in the taxobox.There is still uncertainty, though many are thought to be monophyletic.The Excavata and the chromalveolates are probably only monophyletic if the haptophytes and cryptomonads are excluded.[42]
The type of protist can affect nutrition.The pigments were lost in some groups.Other protists may present phagotrophy, osmotrophy or saprotrophy.There are some that are mixotrophic.Some protists have entered into a relationship with otherbacteria to replace the missing function.A green alga and a cyanobacterium have been captured by Paramecium bursaria.The protist, Mixotricha paradoxa that has lost its mitochondria uses a variety ofbacteria for locomotion.
There are many protists who are flagellate and filter feeding can take place where they find prey.Protists can form a food vacuole by extending their cells around food particles, and then digest them in a process called phagocytosis.
It can be found a heritage among protists for most important cellular structures and functions.[42]
Some species have extremely complex life cycles that involve multiple forms of the organisms, some of which reproduce sexually and others asexually.It's not clear how frequently sexual reproduction causes genetic exchange between different strains of Plasmodium in nature and most populations of parasites don't exchange genes with other members of their species.[46]
More than 1.5 billion years ago, Eukaryotes emerged in evolution.The earliest eukaryotes were protists.Sex is widespread among extant eukaryotes, but it seemed unlikely until recently that it was a primordial and fundamental characteristic.Sex appeared to be lacking in some protists whose ancestors branched off early from the family tree.Several of these protists have recently had the ability to have sexual reproduction.Giardia lamblia was thought to be a descendant of a protist line that predated the emergence of sex.A core set of genes that function in meiosis are found in G. lamblia.The results suggested that G. lamblia is capable of sexual reproduction.Evidence for meiotic recombination, indicative of sex, was found in G.lamblia.[49]
The sexual cycle of the Leishmania protists is similar to the meiosis done in the trypanosomes.50
It is not known if Trichomonas vaginalis undergoes meiosis.They tested for 29 genes that function in meiosis and found 27 of them.The findings suggest that T. vaginalis is capable of meiosis.Most of the meiotic genes were present in G. lamblia.The two species are descendants of protist lineages.It was suggested that the meiotic genes were present in a common ancestor.
Dacks and Roger proposed that facultative sex was present in the common ancestor of all eukaryotes.[52]
This view was supported by a study of amoebae.Amoeba have been seen as sexual protists.The majority of asexual groups likely arose recently and independently, according to the authors.Calkins and other early researchers thought that phenomena in amoeboid organisms were related to sexual reproduction.[54]
Protists reproduce asexually under favorable environmental conditions, but tend to reproduce sexually under stress.Sex in protists appears to be influenced by the production of reactive oxygen species, which can lead to DNA damage.[55]
Toxoplasma gondii is a Protist pathogen that can cause asexual reproduction in a wide variety of animals, but only in the primary or definitive host.There are 56 and 57 words.
Protists live in environments that have liquid water.Many protists, such as algae, are vital primary producers in the ocean as part of the plankton.There is a large amount of protists in both marine and terrestrial environments.[59]
The kinetoplastid Trypanosoma brucei is one of the species that causes sleeping sickness.
Some protists are parasites of animals.There are many species of parasites that cause diseases in humans and other animals.Protist pathogens share many pathways with their hosts.Therapeutic target development is difficult because a drug that harms a protist parasites is also likely to harm its animal/plant host.A more thorough understanding of protist biology could allow these diseases to be treated more efficiently.An attractive target for treating diseases caused by plasmodium is the apicoplast, a nonphotosynthetic chloroplast that is essential to carry out important functions other than photosynthesis.
Researchers from the Agricultural Research Service are using protists to control red imported fire ant in Argentina.Red fire ant populations can be reduced by up to 100% by protists such as Kneallhazia solenopsae.Researchers have been able to kill the flies without harming them.The flies can spread the protist between red fire ant colonies.69