Which Organism From Kingdom Protista Is Most Closely Related To Animals

Learning Objectives

By the end of this department, you volition accept completed the following objectives:

• Identify the evolutionary relationships of plants, animals, and fungi inside the vi presently recognized supergroups of eukaryotes
• Describe representative protist organisms from each of the six presently recognized supergroups of eukaryotes

In the span of several decades, the Kingdom Protista has been disassembled considering sequence analyses accept revealed new genetic (and therefore evolutionary) relationships among these eukaryotes. Moreover, protists that exhibit similar morphological features may have evolved analogous structures because of similar selective pressures—rather than because of recent mutual beginnings. This phenomenon, called convergent evolution, is 1 reason why protist nomenclature is so challenging. The emerging classification scheme groups the entire domain Eukaryota into six "supergroups" that contain all of the protists equally well as animals, plants, and fungi that evolved from a common ancestor (Figure one). The supergroups are believed to be monophyletic, meaning that all organisms within each supergroup are believed to take evolved from a single mutual ancestor, and thus all members are almost closely related to each other than to organisms outside that group. At that place is even so evidence defective for the monophyly of some groups.

Figure 1. This diagram shows a proposed classification of the domain Eukara. Currently, the domain Eukarya is divided into six supergroups. Within each supergroup are multiple kingdoms. Dotted lines indicate suggested evolutionary relationships that remain nether debate.

The nomenclature of eukaryotes is yet in flux, and the 6 supergroups may be modified or replaced past a more appropriate hierarchy as genetic, morphological, and ecological data accrue. Keep in mind that the classification scheme presented here is just ane of several hypotheses, and the true evolutionary relationships are even so to be determined. When learning about protists, it is helpful to focus less on the nomenclature and more on the commonalities and differences that define the groups themselves.

Excavata

Many of the protist species classified into the supergroup Excavata are asymmetrical, single-celled organisms with a feeding groove "excavated" from one side. This supergroup includes heterotrophic predators, photosynthetic species, and parasites. Its subgroups are the diplomonads, parabasalids, and euglenozoans.

Diplomonads

Figure 2. The mammalian intestinal parasite Giardia lamblia, visualized here using scanning electron microscopy, is a waterborne protist that causes severe diarrhea when ingested. (credit: modification of work past Janice Carr, CDC; scale-bar data from Matt Russell)

Amid the Excavata are the diplomonads, which include the intestinal parasite, Giardia lamblia (Figure 2). Until recently, these protists were believed to lack mitochondria. Mitochondrial remnant organelles, chosen mitosomes, take since been identified in diplomonads, only these mitosomes are essentially nonfunctional. Diplomonads exist in anaerobic environments and use culling pathways, such as glycolysis, to generate energy. Each diplomonad cell has two identical nuclei and uses several flagella for locomotion.

Parabasalids

A second Excavata subgroup, the parabasalids, besides exhibits semi-functional mitochondria. In parabasalids, these structures role anaerobically and are called hydrogenosomes because they produce hydrogen gas every bit a byproduct. Parabasalids move with flagella and membrane rippling. Trichomonas vaginalis, a parabasalid that causes a sexually transmitted disease in humans, employs these mechanisms to transit through the male and female urogenital tracts. T. vaginalis causes trichamoniasis, which appears in an estimated 180 million cases worldwide each twelvemonth. Whereas men rarely showroom symptoms during an infection with this protist, infected women may become more susceptible to secondary infection with human immunodeficiency virus (HIV) and may exist more than probable to develop cervical cancer. Pregnant women infected with T. vaginalis are at an increased risk of serious complications, such every bit pre-term delivery.

Euglenozoans

Euglenozoans includes parasites, heterotrophs, autotrophs, and mixotrophs, ranging in size from x to 500 µm. Euglenoids movement through their aquatic habitats using two long flagella that guide them toward low-cal sources sensed past a primitive ocular organ called an eyespot. The familiar genus, Euglena, encompasses some mixotrophic species that display a photosynthetic capability only when calorie-free is present. In the dark, the chloroplasts of Euglena shrink upwards and temporarily finish functioning, and the cells instead have up organic nutrients from their environment.

The human parasite, Trypanosoma brucei, belongs to a different subgroup of Euglenozoa, the kinetoplastids. The kinetoplastid subgroup is named after the kinetoplast, a Deoxyribonucleic acid mass carried within the single, oversized mitochondrion possessed past each of these cells. This subgroup includes several parasites, collectively called trypanosomes, which cause devastating human diseases and infect an insect species during a portion of their life cycle. T. brucei develops in the gut of the tsetse fly after the fly bites an infected human or other mammalian host. The parasite then travels to the insect salivary glands to be transmitted to some other human or other mammal when the infected tsetse fly consumes some other blood meal. T. brucei is mutual in central Africa and is the causative agent of African sleeping sickness, a illness associated with severe chronic fatigue, blackout, and tin can be fatal if left untreated.

Figure 3. Trypanosoma brucei, the causative agent of sleeping sickness, spends part of its life bicycle in the tsetse fly and function in humans. (credit: modification of work by CDC)

Link to Learning

Sentinel this video to encounter T. brucei swimming.

Chromalveolata

Current bear witness suggests that species classified as chromalveolates are derived from a common antecedent that engulfed a photosynthetic red algal cell, which itself had already evolved chloroplasts from an endosymbiotic relationship with a photosynthetic prokaryote. Therefore, the ancestor of chromalveolates is believed to take resulted from a secondary endosymbiotic event. However, some chromalveolates announced to accept lost cherry-red alga-derived plastid organelles or lack plastid genes altogether. Therefore, this supergroup should be considered a hypothesis-based working grouping that is discipline to change. Chromalveolates include very of import photosynthetic organisms, such as diatoms, chocolate-brown algae, and significant disease agents in animals and plants. The chromalveolates can be subdivided into alveolates and stramenopiles.

Alveolates: Dinoflagellates, Apicomplexians, and Ciliates

Figure iv. The dinoflagellates exhibit nifty diversity in shape. Many are encased in cellulose armor and accept two flagella that fit in grooves between the plates. Motility of these ii perpendicular flagella causes a spinning motion.

A large trunk of data supports that the alveolates are derived from a shared mutual ancestor. The alveolates are named for the presence of an air sac, or membrane-enclosed sac, beneath the cell membrane. The exact office of the alveolus is unknown, only it may be involved in osmoregulation. The alveolates are further categorized into some of the meliorate-known protists: the dinoflagellates, the apicomplexans, and the ciliates.

Dinoflagellates exhibit extensive morphological multifariousness and tin be photosynthetic, heterotrophic, or mixotrophic. Many dinoflagellates are encased in interlocking plates of cellulose. Two perpendicular flagella fit into the grooves between the cellulose plates, with one flagellum extending longitudinally and a second encircling the dinoflagellate (Effigy four). Together, the flagella contribute to the characteristic spinning motion of dinoflagellates. These protists be in freshwater and marine habitats, and are a component of plankton, the typically microscopic organisms that drift through the h2o and serve as a crucial food source for larger aquatic organisms.

Figure five. Bioluminescence is emitted from dinoflagellates in a breaking wave, as seen from the New Jersey coast. (credit: "catalano82"/Flickr)

Some dinoflagellates generate light, chosen bioluminescence, when they are jarred or stressed. Large numbers of marine dinoflagellates (billions or trillions of cells per wave) can emit light and cause an entire breaking wave to twinkle or take on a brilliant blue color (Figure 5). For approximately 20 species of marine dinoflagellates, population explosions (as well chosen blooms) during the summer months can tint the ocean with a muddy red color. This phenomenon is called a red tide, and it results from the abundant red pigments present in dinoflagellate plastids. In large quantities, these dinoflagellate species secrete an asphyxiating toxin that tin kill fish, birds, and marine mammals. Ruddy tides can be massively detrimental to commercial fisheries, and humans who consume these protists may become poisoned.

The apicomplexan protists are and so named because their microtubules, fibrin, and vacuoles are asymmetrically distributed at i finish of the cell in a structure called an apical complex (Figure 6). The upmost circuitous is specialized for entry and infection of host cells. Indeed, all apicomplexans are parasitic. This grouping includes the genus Plasmodium, which causes malaria in humans. Apicomplexan life cycles are complex, involving multiple hosts and stages of sexual and asexual reproduction.

Figure 6. (a) Apicomplexans are parasitic protists. They take a characteristic apical circuitous that enables them to infect host cells. (b) Plasmodium, the causative agent of malaria, has a complex life bike typical of apicomplexans. (credit b: modification of work past CDC)

The ciliates, which include Paramecium and Tetrahymena, are a grouping of protists x to three,000 micrometers in length that are covered in rows, tufts, or spirals of tiny cilia. By beating their cilia synchronously or in waves, ciliates can coordinate directed movements and ingest food particles. Certain ciliates have fused cilia-based structures that function like paddles, funnels, or fins. Ciliates also are surrounded by a pellicle, providing protection without compromising agility. The genus Paramecium includes protists that have organized their cilia into a plate-like primitive mouth, called an oral groove, which is used to capture and assimilate leaner (Effigy seven). Food captured in the oral groove enters a food vacuole, where it combines with digestive enzymes. Waste particles are expelled by an exocytic vesicle that fuses at a specific region on the cell membrane, chosen the anal pore. In addition to a vacuole-based digestive arrangement, Paramecium also uses contractile vacuoles, which are osmoregulatory vesicles that fill with water as it enters the cell by osmosis and then contract to clasp water from the cell.

Figure 7. Paramecium has a primitive rima oris (called an oral groove) to ingest nutrient, and an anal pore to excrete it. Contractile vacuoles allow the organism to excrete excess water. Cilia enable the organism to move. (credit "paramecium micrograph": modification of work by NIH; scale-bar data from Matt Russell)

Link to Learning

Watch the video of the contractile vacuole of Paramecium expelling water to go along the cell osmotically balanced.

Paramecium has two nuclei, a macronucleus and a micronucleus, in each prison cell. The micronucleus is essential for sexual reproduction, whereas the macronucleus directs asexual binary fission and all other biological functions. The procedure of sexual reproduction in Paramecium underscores the importance of the micronucleus to these protists. Paramecium and nearly other ciliates reproduce sexually by conjugation. This process begins when two different mating types of Paramecium make physical contact and join with a cytoplasmic bridge (Figure 8). The diploid micronucleus in each jail cell then undergoes meiosis to produce iv haploid micronuclei. Iii of these degenerate in each jail cell, leaving one micronucleus that and then undergoes mitosis, generating two haploid micronuclei. The cells each exchange 1 of these haploid nuclei and movement abroad from each other. A similar procedure occurs in bacteria that have plasmids. Fusion of the haploid micronuclei generates a completely novel diploid pre-micronucleus in each conjugative jail cell. This pre-micronucleus undergoes three rounds of mitosis to produce eight copies, and the original macronucleus disintegrates. Four of the eight pre-micronuclei become full-fledged micronuclei, whereas the other four perform multiple rounds of Dna replication and go on to become new macronuclei. Ii jail cell divisions then yield iv new Paramecia from each original conjugative cell.

Art Connexion

Figure 8. The complex procedure of sexual reproduction in Paramecium creates 8 daughter cells from two original cells. Each cell has a macronucleus and a micronucleus. During sexual reproduction, the macronucleus dissolves and is replaced past a micronucleus. (credit "micrograph": modification of work by Ian Sutton; scale-bar data from Matt Russell)

Which of the following statements about Paramecium sexual reproduction is false?

1. The macronuclei are derived from micronuclei.
2. Both mitosis and meiosis occur during sexual reproduction.
3. The conjugate pair swaps macronucleii.
4. Each parent produces four daughter cells.

Statement iii is false.

Stramenopiles: Diatoms, Brown Algae, Golden Algae and Oomycetes

Figure ix. This stramenopile cell has a single hairy flagellum and a secondary smooth flagellum.

The other subgroup of chromalveolates, the stramenopiles, includes photosynthetic marine algae and heterotrophic protists. The unifying feature of this grouping is the presence of a textured, or "hairy," flagellum. Many stramenopiles also have an additional flagellum that lacks hair-similar projections (Figure 9). Members of this subgroup range in size from single-celled diatoms to the massive and multicellular kelp.

The diatoms are unicellular photosynthetic protists that encase themselves in intricately patterned, glassy prison cell walls composed of silicon dioxide in a matrix of organic particles (Effigy 10). These protists are a component of freshwater and marine plankton. Nigh species of diatoms reproduce asexually, although some instances of sexual reproduction and sporulation also exist. Some diatoms exhibit a slit in their silica crush, called a raphe. Past expelling a stream of mucopolysaccharides from the raphe, the diatom can attach to surfaces or propel itself in i direction.

Figure 10. Assorted diatoms, visualized here using low-cal microscopy, live amongst almanac sea water ice in McMurdo Sound, Antarctica. Diatoms range in size from 2 to 200 µm. (credit: Prof. Gordon T. Taylor, Stony Beck University, NSF, NOAA)

During periods of food availability, diatom populations bloom to numbers greater than tin can exist consumed past aquatic organisms. The excess diatoms die and sink to the sea flooring where they are not easily reached by saprobes that feed on expressionless organisms. Every bit a outcome, the carbon dioxide that the diatoms had consumed and incorporated into their cells during photosynthesis is not returned to the atmosphere. In general, this process by which carbon is transported deep into the ocean is described as the biological carbon pump, considering carbon is "pumped" to the ocean depths where information technology is inaccessible to the temper as carbon dioxide. The biological carbon pump is a crucial component of the carbon cycle that maintains lower atmospheric carbon dioxide levels.

Like diatoms, golden algae are largely unicellular, although some species can form large colonies. Their characteristic gilded colour results from their extensive employ of carotenoids, a group of photosynthetic pigments that are by and large yellow or orangish in color. Golden algae are plant in both freshwater and marine environments, where they form a major role of the plankton community.

The brown algae are primarily marine, multicellular organisms that are known colloquially equally seaweeds. Giant kelps are a type of chocolate-brown algae. Some brown algae accept evolved specialized tissues that resemble terrestrial plants, with root-like holdfasts, stem-like stipes, and leaf-like blades that are capable of photosynthesis. The stipes of giant kelps are enormous, extending in some cases for 60 meters. A multifariousness of algal life cycles exists, only the most complex is alternation of generations, in which both haploid and diploid stages involve multicellularity. Compare this life bicycle to that of humans, for instance. Haploid gametes produced by meiosis (sperm and egg) combine in fertilization to generate a diploid zygote that undergoes many rounds of mitosis to produce a multicellular embryo and then a fetus. Notwithstanding, the private sperm and egg themselves never become multicellular beings. Terrestrial plants also have evolved alternation of generations. In the brown algae genus Laminaria, haploid spores develop into multicellular gametophytes, which produce haploid gametes that combine to produce diploid organisms that then go multicellular organisms with a unlike structure from the haploid form (Figure 11). Sure other organisms perform alternation of generations in which both the haploid and diploid forms look the same.

Art Connection

Figure 11. Several species of brown algae, such equally the Laminaria shown here, have evolved life cycles in which both the haploid (gametophyte) and diploid (sporophyte) forms are multicellular. The gametophyte is different in structure than the sporophyte. (credit "laminaria photograph": modification of work by Claire Fackler, CINMS, NOAA Photo Library)

Which of the following statements nearly the Laminaria life cycle is simulated?

1. 1n zoospores grade in the sporangia.
2. The sporophyte is the twodue north plant.
3. The gametophyte is diploid.
4. Both the gametophyte and sporophyte stages are multicellular.

Statement three is false.

Figure 12. A saprobic oomycete engulfs a dead insect. (credit: modification of work past Thomas Bresson)

The water molds, oomycetes ("egg fungus"), were and so-named based on their fungus-similar morphology, but molecular data have shown that the h2o molds are not closely related to fungi. The oomycetes are characterized by a cellulose-based prison cell wall and an extensive network of filaments that allow for nutrient uptake. As diploid spores, many oomycetes have two oppositely directed flagella (one hairy and i shine) for locomotion. The oomycetes are nonphotosynthetic and include many saprobes and parasites. The saprobes announced as white fluffy growths on dead organisms (Figure 12). Most oomycetes are aquatic, only some parasitize terrestrial plants. I found pathogen is Phytophthora infestans, the causative amanuensis of late blight of potatoes, such equally occurred in the nineteenth century Irish murphy famine.

Rhizaria

Figure thirteen.  Ammonia Tepida, nether a phase contrasty light microscope (credit: modification of work by Scott Fay, UC Berkeley; scale-bar data from Matt Russell)

The Rhizaria supergroup includes many of the amoebas, most of which have threadlike or needle-like pseudopodia (ammonia tepida, a Rhizaria species, can be seen in Effigy 13). Pseudopodia function to trap and engulf food particles and to direct movement in rhizarian protists. These pseudopods projection outward from anywhere on the prison cell surface and can anchor to a substrate. The protist then transports its cytoplasm into the pseudopod, thereby moving the entire jail cell. This blazon of motion, called cytoplasmic streaming, is used past several diverse groups of protists every bit a means of locomotion or equally a method to distribute nutrients and oxygen.

Link to Learning

Accept a expect at this video to see cytoplasmic streaming in a green alga.

Forams

Figure 14. These shells from foraminifera sank to the body of water floor. (credit: Deep East 2001, NOAA/OER)

Foraminiferans, or forams, are unicellular heterotrophic protists, ranging from approximately 20 micrometers to several centimeters in length, and occasionally resembling tiny snails (Figure fourteen). As a group, the forams exhibit porous shells, called tests that are built from diverse organic materials and typically hardened with calcium carbonate. The tests may house photosynthetic algae, which the forams can harvest for nutrition. Foram pseudopodia extend through the pores and permit the forams to move, feed, and gather boosted building materials. Typically, forams are associated with sand or other particles in marine or freshwater habitats. Foraminiferans are besides useful as indicators of pollution and changes in global weather patterns.

Radiolarians

Effigy 15. This fossilized radiolarian crush was imaged using a scanning electron microscope. (credit: modification of piece of work by Hannes Grobe, Alfred Wegener Plant; scale-bar data from Matt Russell)

A second subtype of Rhizaria, the radiolarians, exhibit intricate exteriors of glassy silica with radial or bilateral symmetry (Effigy fifteen). Needle-similar pseudopods supported by microtubules radiate outward from the prison cell bodies of these protists and role to catch food particles. The shells of dead radiolarians sink to the ocean flooring, where they may accumulate in 100 meter-thick depths. Preserved, sedimented radiolarians are very common in the fossil record.

Archaeplastida

Carmine algae and green algae are included in the supergroup Archaeplastida. It was from a common antecedent of these protists that the land plants evolved, since their closest relatives are found in this group. Molecular bear witness supports that all Archaeplastida are descendents of an endosymbiotic relationship between a heterotrophic protist and a cyanobacterium. The reddish and green algae include unicellular, multicellular, and colonial forms.

Ruddy Algae

Scarlet algae, or rhodophytes, are primarily multicellular, lack flagella, and range in size from microscopic, unicellular protists to big, multicellular forms grouped into the informal seaweed category. The red algae life bike is an alternation of generations. Some species of red algae contain phycoerythrins, photosynthetic accessory pigments that are red in color and outcompete the light-green tint of chlorophyll, making these species appear as varying shades of reddish. Other protists classified as red algae lack phycoerythrins and are parasites. Reddish algae are common in tropical waters where they have been detected at depths of 260 meters. Other red algae exist in terrestrial or freshwater environments.

Green Algae: Chlorophytes and Charophytes

The most arable grouping of algae is the dark-green algae. The greenish algae exhibit similar features to the land plants, specially in terms of chloroplast construction. That this group of protists shared a relatively recent mutual ancestor with land plants is well supported. The green algae are subdivided into the chlorophytes and the charophytes. The charophytes are the closest living relatives to land plants and resemble them in morphology and reproductive strategies. Charophytes are mutual in wet habitats, and their presence oft signals a salubrious ecosystem.

The chlorophytes exhibit great diversity of form and function. Chlorophytes primarily inhabit freshwater and damp soil, and are a common component of plankton. Chlamydomonas is a simple, unicellular chlorophyte with a pear-shaped morphology and 2 opposing, anterior flagella that guide this protist toward light sensed by its eyespot. More than complex chlorophyte species exhibit haploid gametes and spores that resemble Chlamydomonas.

The chlorophyte Volvox is i of only a few examples of a colonial organism, which behaves in some ways like a drove of individual cells, but in other ways like the specialized cells of a multicellular organism (Figure sixteen). Volvox colonies contain 500 to 60,000 cells, each with ii flagella, independent within a hollow, spherical matrix composed of a gelatinous glycoprotein secretion. Individual Volvox cells motion in a coordinated fashion and are interconnected by cytoplasmic bridges. Only a few of the cells reproduce to create girl colonies, an example of basic cell specialization in this organism.

Figure xvi. Volvox aureus is a dark-green alga in the supergroup Archaeplastida. This species exists as a colony, consisting of cells immersed in a gel-like matrix and intertwined with each other via hair-like cytoplasmic extensions. (credit: Dr. Ralf Wagner)

Figure 17. Caulerpa taxifolia is a chlorophyte consisting of a single jail cell containing potentially thousands of nuclei. (credit: NOAA)

True multicellular organisms, such as the sea lettuce, Ulva, are represented among the chlorophytes. In addition, some chlorophytes be as large, multinucleate, unmarried cells. Species in the genus Caulerpa exhibit flattened fern-like foliage and tin accomplish lengths of iii meters (Effigy 17). Caulerpa species undergo nuclear segmentation, but their cells do non consummate cytokinesis, remaining instead as massive and elaborate single cells.

Amoebozoa

The amoebozoans characteristically showroom pseudopodia that extend like tubes or flat lobes, rather than the hair-similar pseudopodia of rhizarian amoeba (Figure 18). The Amoebozoa include several groups of unicellular amoeba-like organisms that are free-living or parasites.

Figure xviii. Amoebae with tubular and lobe-shaped pseudopodia are seen nether a microscope. These isolates would be morphologically classified equally amoebozoans.

Slime Molds

A subset of the amoebozoans, the slime molds, has several morphological similarities to fungi that are thought to be the result of convergent development. For instance, during times of stress, some slime molds develop into spore-generating fruiting bodies, much similar fungi.

The slime molds are categorized on the basis of their life cycles into plasmodial or cellular types. Plasmodial slime molds are composed of large, multinucleate cells and move along surfaces like an amorphous blob of slime during their feeding phase (Figure 19). Nutrient particles are lifted and engulfed into the slime mold equally it glides along. Upon maturation, the plasmodium takes on a cyberspace-like appearance with the power to form fruiting bodies, or sporangia, during times of stress. Haploid spores are produced by meiosis within the sporangia, and spores tin exist disseminated through the air or water to potentially land in more favorable environments. If this occurs, the spores germinate to form ameboid or flagellate haploid cells that can combine with each other and produce a diploid zygotic slime mold to consummate the life bike.

Figure xix. The life bike of the plasmodial slime mold is shown. The brightly colored plasmodium in the inset photo is a unmarried-celled, multinucleate mass. (credit: modification of work by Dr. Jonatha Gott and the Eye for RNA Molecular Biology, Case Western Reserve Academy)

The cellular slime molds function as independent amoeboid cells when nutrients are arable (Figure 20). When food is depleted, cellular slime molds pile onto each other into a mass of cells that behaves as a single unit, called a slug. Some cells in the slug contribute to a ii–3-millimeter stalk, drying up and dying in the process. Cells atop the stalk grade an asexual fruiting body that contains haploid spores. As with plasmodial slime molds, the spores are disseminated and tin can germinate if they land in a moist environs. I representative genus of the cellular slime molds is Dictyostelium, which unremarkably exists in the damp soil of forests.

Figure 20. Cellular slime molds may exist as alone or aggregated amoebas. (credit: modification of work past "thatredhead4"/Flickr)

Link to Learning

Watch this video to see the formation of a fruiting body by a cellular slime mold.

Opisthokonta

The opisthokonts include the animal-like choanoflagellates, which are believed to resemble the common antecedent of sponges and, in fact, all animals. Choanoflagellates include unicellular and colonial forms, and number about 244 described species. These organisms exhibit a single, apical flagellum that is surrounded past a contractile collar composed of microvilli. The collar uses a similar mechanism to sponges to filter out leaner for ingestion past the protist. The morphology of choanoflagellates was recognized early on as resembling the collar cells of sponges, and suggesting a possible relationship to animals.

The Mesomycetozoa grade a small-scale group of parasites, primarily of fish, and at to the lowest degree one form that tin can parasitize humans. Their life cycles are poorly understood. These organisms are of special involvement, considering they appear to be and so closely related to animals. In the past, they were grouped with fungi and other protists based on their morphology.

Section Summary

The process of classifying protists into meaningful groups is ongoing, but genetic information in the by 20 years have clarified many relationships that were previously unclear or mistaken. The majority view at nowadays is to order all eukaryotes into six supergroups: Excavata, Chromalveolata, Rhizaria, Archaeplastida, Amoebozoa, and Opisthokonta. The goal of this nomenclature scheme is to create clusters of species that all are derived from a common ancestor. At present, the monophyly of some of the supergroups are better supported past genetic information than others. Although tremendous variation exists within the supergroups, commonalities at the morphological, physiological, and ecological levels tin be identified.

Glossary

biological carbon pump: procedure by which inorganic carbon is stock-still past photosynthetic species that then die and fall to the ocean flooring where they cannot be reached by saprobes and their carbon dioxide consumption cannot be returned to the atmosphere

bioluminescence: generation and emission of light by an organism, every bit in dinoflagellates

contractile vacuole: vesicle that fills with water (every bit it enters the prison cell by osmosis) and then contracts to squeeze h2o from the prison cell; an osmoregulatory vesicle

cytoplasmic streaming: movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod

hydrogenosome: organelle carried past parabasalids (Excavata) that functions anaerobically and outputs hydrogen gas as a byproduct; likely evolved from mitochondria

kinetoplast: mass of Dna carried within the single, oversized mitochondrion, characteristic of kinetoplastids (phylum: Euglenozoa)

mitosome: nonfunctional organelle carried in the cells of diplomonads (Excavata) that likely evolved from a mitochondrion

plankton: diverse group of mostly microscopic organisms that drift in marine and freshwater systems and serve as a food source for larger aquatic organisms

raphe: slit in the silica shell of diatoms through which the protist secretes a stream of mucopolysaccharides for locomotion and attachment to substrates

test: porous shell of a foram that is built from diverse organic materials and typically hardened with calcium carbonate

Source: https://courses.lumenlearning.com/suny-biology2xmaster/chapter/classification-of-protists/

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