What space protists?

They room eukaryotes because they all have actually a nucleus.Most have actually mitochondria return some have later shed theirs (Link). Mitochondria were derived from aerobic alpha-proteobacteria that when lived within your cells.Many have actually chloroplasts through which they bring on photosynthesis. Chloroplasts were derived from photosynthesis cyanobacteria life within your cells.

You are watching: Diatoms dinoflagellates and ciliates are all examples of

Link to a conversation of the "endosymbiosis" theory that the origin of eukaryotes.
Many room unicellular and also all teams (with one exception) contain part unicellular members.The name Protista means "the an extremely first", and also some of the 80-odd teams of organisms that us classify together protists might well have had long, live independence evolutionary backgrounds stretching as far ago as 2 exchange rate years. Yet genome analysis included to various other criteria display that others are acquired from more complicated ancestors; that is, room not "primitive" at all.Genome analysis additionally shows that countless of the groups placed in the Protista room not at all very closely related to one another; the is, the protists perform not stand for a solitary clade.So we consider them below as a group an ext for ours convenience than as a reflection of close kinship, anda much better title because that this page would it is in "Eukaryotes that room neither Animals, Fungi, nor Plants".

The Euglenozoa

Most room unicellular.Many swim by method of a single flagellum.They room not encased in a cell wall surface so they space flexible and also motile.Euglena is a usual member the the group (which numbers about 1600 species). Because some members that the team (like Euglena) have chloroplasts, these organisms used to be referred to as "Euglenophytes", yet in fact they space neither tree ("phytes") nor pets ("zoa"). Fairly — prefer the various other organisms top top this page — they room the living descendants of few of the an extremely earliest eukaryotes. Trypanosoma brucei, the cause of African sleeping sickness in humans, is a member the the group. The electron micrograph (by L. Tetley; courtesy of Keith Vickerman) mirrors T. Brucei as it wake up in the salient gland the the tsetse fly all set to it is in injected into the mammalian organize when the fly bites. The specimen is 12 µm long.
How trypanosomes evade the immune solution of their host.
In Latin America, Trypanosoma cruzi, an additional member that the group, is the reason of Chagas disease in humans.

Ciliates, Sporozoans, and also Dinoflagellates: the Alveolates

These 3 phyla are grouped in a clade — the alveolates — becausethey all have a system of saclike structures ("alveoli") on the inner surface of their plasma membrane as well asclose homology in their gene sequences.


Move through the rhythmic beating of your cilia.Examples: Paramecium, Stentor, Vorticella, Tetrahymena thermophila.Although single-celled, part are huge enough to it is in seen through the nude eye. In fact, the tiny parasitic wasp Megaphragma mymaripenne, v its tens of countless cells (4,600 neurons alone), is no bigger than Paramecium. Feed by sweeping a currently of particle-laden water with a "mouth" and "gullet" and also into a food vacuole.Undigested wastes room discharged at a permanent site.Fresh water ciliates cope with the continuous influx the water from their hypotonic next site by pump it out v one or more contractile vacuoles. Parasitic ciliates, i beg your pardon live in isotonic surroundings, have no contractile vacuole.

All of this rightly suggests that return they room unicellular, over there is nothing rudimentary around the ciliates. Their single cell is far more elaborate in its company than any kind of cell the end of which multicellular organisms are made.

Link to conversation of reproduction in the ciliates.

Sporozoans (Apicomplexa)

The members that this team share one "apical complex" the microtubules in ~ one end of the cabinet (hence the surname that many prefer come the old surname of sporozoans). All the members of the phylum are parasites.

The genus Plasmodium reasons malaria, among the biggest scourges of humans. There space 4 species that infect people of i beg your pardon Plasmodium falciparum is the many dangerous. Malaria has probably caused much more human deaths than any other contagious disease; also today the is approximated to death a million civilization a year in the sub-Saharan Africa.

The organism is sent from person to human being through the bite the mosquitoes of the genus Anopheles.

The diagram reflects the Plasmodium life cycle.

The mosquito bite injects sporozoites into the person host.These attack the liver wherein they build into merozoites.The merozoites attack red blood cells where they reproduce.Periodically, lock all an outbreak of the red cells together bringing on the chills and also fever characteristic of the disease.Eventually part merozoites develop into either male or female gametocytes.These will die unless they room sucked increase by the bite of an anopheline mosquito.Once in the stomach of the mosquito, the gametocytes type gametes: sperm and eggs.These fuse to form zygotes.The zygote invades the stomach wall of the mosquito developing thousands of sporozoites.These migrate to the salient gland, ready to it is in injected into a new human host.

Most forms of malaria space chronic. The organisms may coexist v their organize for years (but cannot finish their life bicycle there).
How castle evade the immune solution of their host.
Toxoplasma gondii is an additional parasitic member the this group.

Plasmodium, Toxoplasma, and also some the the other members that this group contain a membrane-enclosed organelle called the apicoplast. They it seems to be ~ to have actually inherited the from a typical ancestor that obtained it through engulfing a chloroplast. Connect to a discussion of this example of secondary endosymbiosis.


About 1000 species.Most are unicellular.Most usage chlorophylls a and also cUnlike most eukaryotes, they lack histones on their chromosomes andhave a simpler form of mitosisThey do have the eukaryotic type ("9 + 2") that flagellum (two of them in fact).Occasionally lock reproduce explosively, producing poisonous red tides that may cause extensive death of maritime fish and make filter-feeding marine animals like clams unfit for person consumption.

Diatoms, golden Algae, Brown Algae, and also Water Molds: The Stramenopiles

These biology belong come a single clade, the stramenopiles (a/k/a heterokonts). The first three members share:a yellow-brown colors (which gives them your color). It is a carotenoid dubbed fucoxanthin.chlorophylls a and c

All 4 of lock (plus a variety of other groups not listed) share gene closely-homologous to those in both green and also red algae. This suggests that they room all lower from a heterotrophic eukaryotic ancestor that obtained both a environment-friendly alga and a red alga through a an additional endosymbiosis. (While the water molds no longer are photosynthetic, castle still maintain both green and also red alga genes.)



Diatoms room unicellular. Your cell wall surface or shell is do of two overlapping halves. These room impregnated with silica and also often beautifully ornamented. The photograph (courtesy the Turtox) is the Arachnoidiscus ehrenbergi enhanced some 400 times.

Diatoms are significant producers in aquatic environments; the is, they are responsible for as much as 40% of the photosynthesis that occurs in new water and in the oceans. They offer as the main base the the food chains in this habitats, giving calories to heterotrophic protists and tiny animals. These, in turn, feed bigger animals.

Golden birds (Chrysophyta)

Most space unicellular.Found in fresh water.Important producer in some aquatic food chains.In short light conditions, may lose their chlorophyll and turn heterotrophic feeding top top bacteria and/or diatoms.Over 1000 types alive today; many more in the fossil record.

Brown birds (Phaeophyta)

The rockweeds and also kelps. Part kelps grow as long as 30 meters.All space multicellular return without lot specialization of cabinet types.Most are uncovered in salt water.Used because that food in some coastal areas of the world and harvested in the U. S. Because that fertilizer and as a resource of iodine.

Water Molds (Oomycetes)

As their name suggests, water molds were once thought about to it is in fungi. However unlike fungi, the cell wall surface of water molds is do of cellulose, not chitin. Furthermore, your gene order are very different from those of fungi (and most carefully related come those the diatoms, golden and brown algae).

Some noteworthy water molds:Some species (e.g., Saprolegnia, Achyla) are parasites of fishes and can it is in a serious trouble in fish hatcheries.Downy mildews damages grapes and other crops.Phytophthora infestans, the reason of the "late blight" of potatoes. In 1845 and also again in 1846, it was responsible because that the almost total destruction of the potato chop in Ireland. This resulted in the an excellent Irish starvation of 1845–1860. During this period, approximately 1 million human being starved come death and also many an ext emigrated come the brand-new World. By the end of the period, death and emigration had diminished the populace of Ireland native 9 million come 4 million.Phytophthora ramorum, i beg your pardon is currently killing several species of oaks in California.

Red algae (Rhodophyta)

The red algae are virtually exclusively marine.Some room unicellular but most room multicellular.Approximately 7000 varieties have been identified.They are photosynthetic utilizing chlorophyll a.Their closest loved ones are the eco-friendly algae and also land plants.Like the cyanobacteria, they use phycoerythrin (which provides them red) andphycocyaninas antenna pigments.They have actually neither centrioles no one the eukaryotic bio "9+2" flagellum.Their genomes are small, and also their gene have couple of introns.Some are used as food in coastal regions the Asia.Agar, the base because that culturing bacteria and also other microorganisms, is extract from a red alga.

Slime Molds (Mycetozoa)

Cellular Slime Molds

The biology in this team have a complicated life cycle during the course of which they go through unicellular, multicellular, funguslike (form spores) and also protozoanlike (amoeboid) stages.

Thousands of separation, personal, instance amoebalike cells aggregate into a slimy massive — each cell retaining its identity (unlike plasmodial slime molds). The aggregating cells room attracted to each other by the cyclic AMP (cAMP) the they release.

With the exception of one types that causes powdery scab on potatoes, these organisms are of tiny economic importance. However, their mix of traits renders them of an excellent scientific interest. Molecular phylogenies place them in the exact same clade as animals (metazoa) and fungi. The link below will present you to one of the most famous members the the group.

External Link
Dictyostelium discoideum: Model mechanism in activity
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Plasmodial (Acellular) Slime Molds (Myxomycetes)


At one phase in their life cycle, these organisms covers a spreading, slimy, multinucleate mass called a plasmodium the moves gradually over that substrate (e.g., a rotting log) engulfing food and growing together it does so. Eventually, the plasmodium establishes stalks that produce and release spores. If the spores floor in a perfect location, lock germinate forming single cells that move by both flagella and pseudopodia. This fuse in pairs and also start creating a brand-new plasmodium.

The left photo (courtesy the Prof. I. K. Ross) reflects the plasmodial phase of Stemonitis just prior to it created sporangia. The right photograph (courtesy the Turtox) mirrors the completely developed sporangia the Stemonitis.

Physarum polycephalum, another member of this group, is the subject of numerous laboratory studies.

External Link
PhysarumPlus — one Internet source for college student of Physarum polycephalum and also Other Acellular Slime Molds
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Protists without common mitochondria

There space several teams of protists the were lengthy thought to have actually no mitochondria. However, most (perhaps all) had actually them in the past. Today, only remnants of your ancestor"s mitochondria — referred to as mitosomes — remain.

Some instances are:MicrosporidiaAll room unicellular obligate intracellular parasites.Many room pathogenic in insects (one is even marketed commercially as a biocontrol agent).Some contaminate drinking water supplies and also can cause gastrointestinal upsets in humans. Microsporidia, such as Encephalitozoon cuniculi, room a common reason of diarrhea in AIDS patients. Encephalitozoon cuniculi has actually a tiny genome with just 1,997 protein-encoding genes — fewer than many bacteria (e.g., E. Coli has actually 4,290). Obliged come live in ~ the cell of that is host, it has lost the gene for many important functions (e.g., the citric mountain cycle) depending instead on the host.Fungi space their closest relatives.Entamoeba histolytica. Causes amebic dysentery, the third most typical parasitic an illness of human beings (after malaria and also schistosomiasis). The closest family members are the slime molds.Giardia intestinalis (also well-known as Giardia lamblia)Frequently encountered in publicly water supplies contaminated by pet feces. Reasons diarrhea in humans. Prevents the host immune response by periodically transforming its surface ar protein coat.



These are single-celled (e.g., Monosiga), aquatic (both new water and also marine) protists that have a single flagellum surrounding by a collar ("choano" = collar) that microvilli. Part (e.g., Proterospongia) kind simple nests during part of your life. The flagellum is offered for swim and additionally beats bacteria-containing water with the collar because that feeding.

Sponges also use collar cells to filter food indigenous the water.

Not only does this imply a nearby relationship between the two groups, yet other proof indicates that choanoflagellates space the closest protistan loved ones of all pets (metazoa). Although solitary cells, they express genes for several proteins the are necessary to cell-cell interactions in metazoans, together ascadherins (attach cells to each various other — Link)tyrosine kinases (used in many examples of cell-cell signaling — Link)chondroitin sulfate (essential component of the connective organization of pets — LinkWhat attributes these proteins have actually in the single-celled choanoflagellates stay to it is in discovered.

Other teams of Eukaryotes

The metazoa (animals) are explained in two separate pages:The Invertebrates andThe VertebratesThe fungi are questioned in a web page of their own. Link to it.Plants, consisting of the green algae are explained in a different page. Attach to it.

See more: How Many Outlets And Lights On A 20 Amp Circuit ? How Many Outlets On A 20

External Link
A portal into the various groups of protists (and other eukaryotes) with many illustrations in color.
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19 respectable 2019