22.+Protists

__**Introduction**__ Protists: Protistans are most like the earliest eukaryotes yet differ from the prokaryotes. They posses many defining characteristics. Eukaryotic cells have a Nucleus, large ribosomes, mitochondria, ER, and Golgi Bodies, cytoskeletal elements, and other membrane bound organelles. As opposed to prokaryotic cells which usually only have one chromosome with multiple plasmids, protists have multiple chromosomes with DNA attached to histone proteins. Protists divide by mitosis and meiosis, and there are many different species. Protists are most like Eukaryotic cells and multiple species utilize various means of feeding. There are Photoautotrophs, Predators, Parasites, and Decomposers (saprobs). Some protistans also produce spores.

__**Parabasalids and Diplomonads**__ Protozoa means “first animal”. There are two main categories of flagellated protozoans: //parabasilids// and //diplomonads//. All flagelated protozoans are heterotophic cells and are defined by the presence of one or more flagella. Parabasalids are predatory and/or parasitic cells. They are heterotrophic and have bundled microtubules throughout the cell. an example od a protozoan that is parasitic is //Trichomonas vaginalis.// It has 4 anterior flagella and attaches to the epithelial linings of the vagina or male reproductive tract. In doing so, it sucks the nutrients out of the respective places Diplomonads have a total of four flagella. Three flagella are at the anterior end while one is at the trailing end. Some diplomads have a few membrane-bound organelles. Cells usually survive outside the body in //a Cyst,// a body covering of cell secretions that helps the cell resist stressful conditions. An example of a diplomad is the //Giardia lamblia,// which //c//auses giardiasis. Both Diplomonads and Parabasalids are heterotrophic flagellates (meaning they feed by ingestion and have flagella for motility). They live in various environments ranging from aerobic to anaerobic ones. They also contain a rudimentary version of the mitochondria; some have a few functioning mitochondria as well. The absence of well-developed mitochondria and some other organelles suggests that the ancestors of parabasalids and diplomonads were among the first eukaryotic cells

__**Euglenoids and Kinetoplastids**__ Euglenoids are a classic example of an evolutionary puzzle. They are free-living, flagellated cells abound in freshwater and stagnant pools. Most are photoautotrophs and some are heterotrophs. They have thickened flagellum approximately five times the normal size. The Euglenoids are assumed to have aquired their chloroplasts by way of endosymbiosis. They have chlorophyll a, chlorophyll b, carotenoids (just as green algea and plants). At the anterioir end euglenoids have an "eyespot" that serves as a photoreceptor able to detect light so that the organism can swim towards the light source. Like some of the protozoas, the euglenoids have a flexible body covering with many spiral strips of a translucent, protein-rich material called a //Pellicle.// A high internal solute concentration leads to diffusion of water into the cells, but contractile vaculoes push the water out through pores. The Euglenoids reproduce by an asexual process called //Binary Fission//, where the cell makes copies of its internal structures and DNA then divides in half along its length, thus forming two daughter cells. Kinetoplastids are heterotrophic, colorless flagellates that incorporate large amounts of mitochondrial DNA. In Kinetoplastids the mitochondrion is very large, almost as large as the entire cell. Most mitochonrion gene products deal with ATP formation under anaerobic or aerobic conditions. A majority of the kinetoplastids are parasites. One in particular that is very harmful to humans is the //Trypanosoma brucei//, which causes African sleeping sickness, chagas disease, etc in humans. Of the Trypanosomes, 500 of kinetoplastids, 2 kinds (Trypanosoma and Leishmania) are disease agents link to Trypanosoma brucei picture: http://www.pnas.org/content/100/3/F1.medium.gif
 * [[image:http://www.infovisual.info/02/img_en/001%20Structure%20of%20a%20euglena.jpg width="307" height="278" align="center" caption="Euglena Protist (1)" link="http://www.infovisual.info/02/img_en/001%20Structure%20of%20a%20euglena.jpg"]]
 * The majority of euglenoids are photoautotrophs. Nearly all kinetoplastids are parasites. Both have thick flagellum that hints at shared ancestry. Internal parasites of some flagellate lineages cause serious desieses in humans.

__**Foramiferans and Radiolarians**__ Foraminiferans are members of rhizopod group. They are single-celled heterotrophs that live in water and posses a continually-changing cytoskeleton. Initially the cells are in a one-chambered shell, but as they grow they add more chambers and then occupy them. The Foraminiferans have pseudopods that interconnect through endocytosis and pinocytosis. They are a protist that has survived since Cambrian times and have been evolutionary adaptive. The Radiolarians are members of the Actinopod (ray feet) group. They have a distinct shell that has an outer layer with vacuoles (help with buoyancy and predation) and a perforated shell made of silica rods. Some Radiolarians are part of marine //plankton//, microscopic organisms that drift and swim weakly in the water. Most of the cells live in the deep ocean water at depths of around 5000m
 * Foraminiferans
 * [[image:bio3tuttle:foram1.jpg width="240" height="205" caption="Foraminiferan (2)" link="https://bio3tuttle.wikispaces.com/file/view/foram1.jpg"]]
 * Radiolarians
 * [[image:http://www.ucmp.berkeley.edu/people/klf/MicroGalleryLarge_files/Radiolarian2.jpg width="235" height="256" caption="Radiolarian (3)" link="http://www.ucmp.berkeley.edu/people/klf/MicroGalleryLarge_files/Radiolarian2.jpg"]]

Alveolates are a monophyletic group consisting of ciliates, dinoflagellates, and apicomplexans. Cells have small membrane bound sacs under plasma membrane (called alveoli).
 * __Alveolates__**

Ciliated Alveolates The habitats of choice for ciliated alveolates are seas and freshwater. They get their nutrition from being heterotrophic. 1/3 of known species are parasites and endosymbionts. Their food sources include Bacteria, Algae, other ciliates. The chloroplasts of algal prey are not often digested. Some ciliated alveolates have bacterial symbionts. A good example of the ciliated alveolates is the //Paramecium. Notice the presence of two nuclei: one micronucleus and one macronucleus. (this makes reproduction more intricate)// //Paramecium// has cilia around its entire body surface, which beat in synchrony. Food is taken in with enzyme-filled vesicles and sychronized beating fo the cilia to sweep food into the area near the gullet. The gullet produces the food filled vesicles which later are fused with lysosomes for digestion. The //Paramecium// also contains contractile vacuoles and a //Pellicle// that has sacs, which store calcium ions used for motility and cytoskeletal movement. There are a multitude of trichocysts (harpoons) on the pellicle and plasma membrane. The trichocysts are bottle shaped capsules with a barb at the end. The Ciliated Alveolates reproduce both asexually and sexually. (Asexual the protists reproduce through binary fission. The plane of division is longitudinal for euglenoids, transverse for ciliates, and random for amoebas)
 * [[image:http://www.infovisual.info/02/img_en/004%20Structure%20of%20a%20paramecium.jpg width="393" height="351" align="center" caption="Paramecium (4)" link="http://www.infovisual.info/02/img_en/004%20Structure%20of%20a%20paramecium.jpg"]]

The process of asexual reproduction is: first the small //diploid micro//nucleus undergoes mitosis, then a large //macro//nucleus lengthens and splits in two (inefficiently; DNA may leak out).

The process of sexual reproduction in ciliates is unique and noticeably different from "normal" reproduction methods. First the partner ciliates repeatedly divide their micronuclei, then swap two daughter micronuclei. Then they let 2 other micronuclei to fuse, making a diploid macronucleus (replacing the one that disappears in the process). During the process the macronuclues is disintegrating. //See pg. 371// //for a helpful diagram of this process.// also see: __http://www.ciliate.org/images/amitvsconj.jpg__

Dinoflagellates are differentiated from ciliated alveolates in that they produce flagellated cells at some point in their life cycles. The 4,000 known species of dinoflagellates live in freshwater or marine environments. Heterotrophs make up half of the known species; these prey on bacteria and algae or parasites fish and crustaceans. The other half of the dinoflagellates, the photoautotrophs, had chloroplasts that originated from red or green algae through a symbiotic process. The dinoflagettes form an "armor plate" in the pellicle, made from deposits of cellulose in their alveoli. Those species that have a thin deposits are called "unarmored." Most dinoflagellates have 2 flagella tht are both in the pellicle. One is attached at the cell's midsection in a longitudinal groove and the other in a transverse groove.
 * __Flagellated Alveolates__**

Like other photoautotrophic cells, dinoflagellates can undergo algal blooms, in which a liter of water holds millions of cells, that occur when warm, shallow water becomes enriched with nutrients and provides a perfect location for dinoflagellates to flourish. Certain dinoflagellates tint the water red; this is sometimse called //red tide//.

Metabolic waste sickens and kills marine life. Toxins of certain dinoflagellates can also kill marine life. In addition, after the burst of alveolate growth, aerobic bateria decompose the remains and oxygen levels in the water are severly decreased, causing aquatic animals to suffocate. For example //Karenia brevis,// that often blooms along the Gulf of Mexico and Atlantic seaboard has a toxin that binds to sodium pumps and disturbs nerve cell functioning. It can cause neurotoxic shellfish poisoning in humans. Blooms have killed billions of fish and sickened or killed various other marine life.



Apicomplexans are parasites which in the adult form have no flagella or cilia, but are flagellated alveolates since their gametes are flagellated. They have an unusual microtubular device that attaches to and pierces a host cell. Many species have plastids, like those in red algae, that may have endosymbiotic origins. An example is, //Plasmodium,// below, which causes malaria.

Malaria is transmitted by //Anopheles// mosquitoes by transferring maturing //Plasmodium// gametes to a host. //Plasmodium// zygotes develop inside the gut of the female //Anopheles// mosquitoes and become sporozites. They then migrate to the salivary glands for the mosquito's next bite. Some sporozites travel in the blood vessels of a human into the liver cells and reproduces asexually by repeated fissions. Some of the offspring become merozoites that reproduce in the red blood cells, which they rupture and kill. Other sporozites enter red blood cells and cause the symptoms of malaria.

Symptoms of malaria are shaking, chills, fever, and sweats. Infected indivuals, though they feel healthy, should expect a relapse. Malaria is historically most prevalent in tropical and subtropical regions of Africa. Currently, cases in North America are steadily increasing.

Artemisinin, a compound isolated from sweet wormwood, has the promise of a treatment for malaria's symptoms. Vaccines are preparations that are intentionally introduced to the body's immune system such that the immune system has the ability to recognize the pathogen when/if it arrives. Efforts for a vaccine for malaria are ongoing. __**Photosynthetic Stramenopiles**__ These organisms make up a group of stramenopiles that primarily acquire nutrients through photosynthesis. Two major subdivisions of the photosynthetic stramenopiles are the chrysophytes and the brown algae. Chrysophytes are "free-living" cells that contain the //a//, //c1// and //c2// chlorophylls. Organisms in this group are the golden algae, yellow-green algae, coccolithophores and the diatoms. The golden algae are all producers in the food chain and contain the fucoxanthin, or golden-brown carotenoid, pigment (which explains its golden-brown color). There are about 500 species of golden algae, many of which are covered by hard structures like silica scales. Yellow-green algae, on the other hand, do not contain any of the fucoxanthin carotenoid. This algae is a little more diverse than the golden algae, for it has 600 or so known species. These yellow-green algae commonly are seen as components of phytoplankton, which are producers and are near the top of the food chain for marine life. Most of these species do not regularly move, but they all produce gametes that are flagellated. They can be found in places such as marshes, oceans and wet soil. Many coccolithospores are single-celled and photoautotrophic. These chrysophytes are covered and protected by plates made of calcium carbonate that form under the plasma membrane. These plates have come together in the past to make ocean sediments and rock and mineral deposits. Coccolithospores usually live in nutrient-poor aquatic habitats, but during algal blooms, they can grow to such a number that they start clogging the gills of fish living in the same habitat. One of their metabolic wastes, dimethyl sulfide, is noxious enough to deter migratory fish from their normal routes.  There are about 5600 existing species of diatoms. These species all have silica “shells” that overlap (like a pillbox) that are used for protection. For millions of years now, these shells have been ground and have accumulated at the bottoms of seas and lakes and are used for insulation, abrasives and filters. These diatoms are also producers that reproduce quite quickly.

 Brown algae are usually the olive-green and brown seaweeds common among rocky shores at low tide. There are about 1500 known species of brown algae. These species live in temperate or cool seawater, anywhere from the intertidal zone through the open ocean. They also contain carotenoids and range in size from microscopic filaments to giant kelps (which are usually 20 to 30 meters long). The structure of giant kelps usually consists of bladders (which are hollow and filled with gas to keep the blades and stipe upright in water), blades (leaf-like structures), stipes (stem-like structures) and holdfasts (anchoring structures). These kelps have sexual and asexual phases, where gametophytes alternate with sporophytes in the life cycle. These giant kelp act as ecosystems, for a myriad of organisms live inside and on them. __**Colorless Stramenopiles**__ Colorless stramenopiles are part of the large evolutionary branching, the stramenopiles. These species are all oomycotes, which literally means egg fungi. The organisms belonging to this branching have diploid nuclei, whereas fungi have haploid nuclei. Also, cell walls of these stramenopiles are made up of cellulose, rather than the chitin in fungi. The sperm of these organisms have double-flagellated sperm. These organisms are also mainly saprobic, or decomposers. They break down dead or decaying material. Water molds are decomposers of aquatic habitats, but many parasitize plants or attack fish or other marine organisms. __**Red Algae**__ Most of the 4100 known species of red algae are marine, but only 200 live in fresh water. They usually live in warm marine currents or tropical seas, but they are found deep in the ocean. These red algae provide the foundation for coral reefs, and their chloroplasts hold phycobilins (red accessory pigments) and chlorophyll //a//. Also, the chloroplasts of red algae are similar to cyanobacteria; this similarity suggests some sort of endosymbiotic origins for these organisms. The species all have single-celled organisms, though some have shown to branch multicellular growth in the life cycle but do not form tissues. The gametes of these organisms have non-flagellated gametes and humans find a variety of uses for species of red algae, whether as food or as a source of agar. . 
 * __Green Algae__**

Green algae are the closest relatives of land plants. They are both single-celled and multi-celled organisms. They live in fresh water habitats and are all photosynthetic. There are over 7000 classified species of green algae. The relatives of green algae, charophytes, are photoautotrophic, more related to land plants than green algae and contain few symbionts of invertebrates and fungi. Both green algae and plants have chloroplasts with chlorophylls //a// and //b//, store sugars as starch grains and have cellulose reinforcing the cell wall. On the other hand, as opposed to plants, most green algae are aquatic. Examples of green algae are //Ulva// and //Chlorella (//A protist used by Melvin Calvin to provide evidence for the light-independent reactions in chloroplasts) and //Chlamydomonas// (of which 16 daughter cells can result from cell division; these organisms can also reproduce sexually and asexually). Introduction to Amoeboids: Most members are shape-shifters that move through cytoplasmic extensions and have no permanent motile structure. Many are solitary, but some express communal behavior. The groups that make up the Amoeboid protozoans are: naked amoebas, foraminiferans, heliozoans, and radiolarians. One of the defining features of these cells is the // Pseudopod, //(false feet) a Lobe of cytoplasm which extends as microtubules assemble. Amoebas are soft-bodied, free-living predators in freshwater habitats. They eat bacteria, other protists, and small multicelled animals through the process of endocytosis/phagocytosis. They are single celled organisms that move on/with pseudopods. An example of an Amoeba is // Entamoeba histolytica, //which infects people through water as a vector and feeds on bacterial cells in intestinal tract. The Ameoba can cause amoebic dysentery.
 * __ Amoeboid Cells __**

Slime Molds are often referred to in slang as “Social Amoebas”. They are free-living, amoeba-like cells for part of the life cycle, and, like amoebas, are predators. There are cellular and plasmodial slime molds. When nutrients are scarce, starving amoebas gather into a slimy mass that may migrate to a better place to feed and for a spore-bearing structure. This process is vital for nutrient cycling in the ecosystems.

Plasmodial slime molds are plasmodium in a stage of its their cycle, then turn into a multinucleated mass that can arise from a single diploid cell by multiple mytosis occurrences // without //cytokinesis. This in turn gives rise to spore-bearing fruiting bodies. Each fruiting body is a cluster of haploid spores on a cellular stalk. The spores germinate when conditions improve.

Cellular slime molds spend most of their life cycle as amoeboid cells. They feed on bacteria and reproduce asexually, by mitosis. They also partake in an interesting form of reproduction. Sometimes environmental stimuli force the molds to shift its life style. The cells aggregate and produce a slug-like form. Then the slug slowly rises and produces a mature fruiting body.

Cellular slime mold picture; [|http://imagecache2.allposters.com/images/pic/PTGPOD/OSDED-00000041-001~Cellular-Slime-Mould-Dictyostelium-Discoideum-Sorocarp-Containing-Spores-Posters.jpg] Sources: Biology //The Unity and Diversity of Life//, Starr Taggart, 10th and 11th editions
 * 1) Euglena Picture- http://www.infovisual.info/02/img_en/001%20Structure%20of%20a%20euglena.jpg
 * 2) Foraminiferan Picture- https://bio3tuttle.wikispaces.com/file/view/foram1.jpg
 * 3) Radiolarian Picture - http://www.ucmp.berkeley.edu/people/klf/MicroGalleryLarge_files/Radiolarian2.jpg
 * 4) Paramecium Picture- http://www.infovisual.info/02/img_en/004%20Structure%20of%20a%20paramecium.jpg
 * 5) K. brevis Picture - http://www.marine.usf.edu/microbiology/images/k-brevis-scan.jpg
 * 6) Plasmodium Picture - http://upload.wikimedia.org/wikipedia/commons/3/3c/Plasmodium.jpg
 * 7) Life Cycle of Plasmodium Picture - http://www.emro.who.int/rbm/Images/MalariaLifeCycle-1.gif
 * 8) Diatomaceous Earth Picture - http://www.holocaust-history.org/auschwitz/zyklonb/Sample3-diatomaceousearth.jpg
 * 9) Amoeba proteus Picture - http://www.oberlin.k12.oh.us/talent/isp/reports2002/amoebaproteus/images/Amoeba%202.jpg
 * 10) Antithamnion - http://media-2.web.britannica.com/eb-media/46/95346-004-728CB09A.jpg