Protist a: Rhizari What Is A Protist? Protist means the very first They are mostly unicellular, but some are multicellular (algae). Protists can be heterotrophic or autotrophic. Most protists live in water, although there are some that live in moist soil or even the human body. ALL protists are eukaryotic, meaning they have a nucleus. Protists are extremely important to human life, they help us recycle, eliminate organic wastes and bacteria, and they are also crucial in the production of many medicines, vaccines, and other medical
advancements. Lots of pretty protists! Rhizopods The phylum Rhizopoda includes a large group of protists that move by means of pseudopods (fake feet), extensions of the cytoplasm. Most Rhizopodians use their pseudopodia to capture prey and also for locomotion. Rhizopods are heterotrophic, feeding on a wide range of bacteria, algae and other protists. Rhizopods are found in freshwater, marine habitats, and in soil. Foraminifera
Domain: Eukaryota Kingdom: Rhizaria Phylum: Foraminifera Foraminifera (forams for short) are unicellular protists with shells. Their shells are also referred to as tests because in some forms the protoplasm covers the exterior of the shell. The shells are commonly divided into chambers which are added during growth, though the simplest forms are open tubes or hollow spheres. Depending on the species, the shell may be made of organic compounds, sand grains and other particles cemented together, or crystalline calcite. Forams are highly porous in structure, having millions of small holes in their shells. They move and catch their food with a network of thin extensions of cytoplasm called reticulopodia, similar to the pseudopodia of an amoeba, although much more numerous
and thinner. The reticulopodia emerge from the pores of the shell, and extend outwards. Forams are the most common marine plankton species. Forams Continued Of the approximately 4000 living species of foraminifera the life cycles of only 20 or so are known. There are a great variety of reproductive, growth and feeding strategies, however the alternation of sexual and asexual generations is common throughout the group. An asexually produced haploid generation commonly
form a large proloculus (initial chamber) and are therefore termed megalospheric. Sexually produced diploid generations tend to produce a smaller proloculus and are therefore termed microspheric. The largest living species have a symbiotic relationship with algae, which they "farm" inside their shells. The most unique aspect of forams is that their benthic prehistoric fossils can be found by the millions on ocean floors, they are particularly useful for dating sediments and rocks with great accuracy. The pink sands of some Bermuda beaches get much of their color from the pink to red-colored shells of a foraminiferan. In regions of the deep ocean far from land the bottom is often made up almost entirely of the shells of planktonic species. Amoebas
Domain: Eukaryota Kingdom: Protista Phylum: Tubulinea Amoebas were originally named Proteus animalcule, after the Greek god Proteus, who could change his shape. Amoebas are unicellular organisms , they use their pseudopodia to move and engulf food particles (phagocytosis). They will eat anything that is smaller than themselves, usually bacteria or protozoans. Amoebas have one or more nuclei, a simple contractile vacuole that helps keep maintain osmotic equilibrium
(osmoregulation), a membrane to let things in and out of the cell, and a food vacuole for engulfed food particles. Amoebas Continued When amoebas move, they extend their pseudopodium, anchor their tips, and then more cytoplasm streams into the pseudopodium. Amoebas inhabit both freshwater and marine environments, and are also abundant in soils. The majority of amoebas are free-living, but some are important parasites including Entamoeba
histolytica, which causes amoebic dysentery, an infection of the intestines marked by severe diarrhea with blood in humans. Amoebas usually reproducs asexually by a process called binary fission (splitting in two), in which the cytoplasm simply pinches in half and pulls apart to form two identical organisms Amoebas are helpful when they control algae in ponds, lakes, and streams. They also provide small animals with food. Amoebas are a problem when they live in unhealthy areas, such as places with raw sewage. Amoebas can range in size from .5 mm to 3 mm or more! Brain Eating Amoeba! While most amoebas are benign, there are a select few that cause considerable damage to humans. In the summer of 2011, there were 8 deaths caused by an amoeba that was
found in rivers. The amoeba, called Naegleria fowleri, is the only type that infects humans and is more than 95% lethal. The first death in 2011 occurred in June in Louisiana, according to the CDC. The amoebas enter the human body through the nose after an individual swims or dives into warm fresh water, like ponds, lakes, rivers and even hot springs. But when an amoeba gets lodged into a person's nose, it starts looking for food. It ends up in the brain and starts eating neurons. Early symptoms include headache, fever, nausea, vomiting and neck stiffness. Later symptoms include confusion, lack of attention to people and surroundings, loss of balance, seizures and hallucinations. The amoeba multiplies, and the body mounts a defense against the infection. This, combined with the rapidly increasing amoebas, cause the brain to swell, creating immense pressure. At some point, the brain stops working. Radiolarians
Radiolaria are protozoa distinguished 1) by segregation of their soft anatomy into the central capsule, containing the endoplasm, and the surrounding ectoplasm, and 2) by their siliceous (glassy) skeletons of the large majority of species. Radiolarians have existed since the beginning of the Paleozoic era, producing an astonishing diversity of intricate shapes during their 600 million year history. They take their name from the radial symmetry, often marked by radial skeletal spines, characteristic of many forms. The central capsule is enclosed in a membrane. It contains not only the nucleus but mitochondria (respiratory organelles) and Golgi bodies (secretory organelles), as well as vacuoles, lipid droplets, and food reserves. Reproduction, respiration, and biochemical synthesis are functions carried out in the central capsule. The ectoplasm extends into a complex network of pseudopodia, called axopods. Axopods aid the in the buoyancy of these organisms. Pseudopodia surround projecting skeletal spines, protecting them from dissolution in sea water. The pseudopods may be quite active,
capturing prey and disposing of wastes, and reacting to external stimuli. They are able to cling to and move the individual about surfaces of laboratory vessels, and may thus cling to foreign objects in nature. Radiolarians Continued Radiolarians are mostly marine plankton. Reproduction of radiolarians can occur both sexually and asexually. Radiolarians also participate in symbiotic relationships with algae, especially zooxanthellae. Radiolaria are also separated into two separate lineages, polycystina, and spasmaria. When radiolarians die, they become ooze at the bottom of the sea. Radiolarians, like forams, are used in the fossil record for dating. Slime Molds
Slime molds are independent organisms that mass together and move as a group to find new nutrition sources. Their name refers to a period in their lives where they seem to be a mass of gelatinous slime. Slime molds reproduce with spores, they are usually found in soil, lawns, and forest floors. Slime molds feed off dead plant matter. The plasmodial slime molds form a structure called a plasmodium, a mass of cytoplasm that contains many nuclei but has no cell walls or membranes to separate individual cells. The plasmodium is the feeding stage of the slime mold. It moves much like an amoeba, slowly sneaking along decaying organic material.
Acrasiomycota Acrasiomycota are cellular slime molds that are haploid blobs that live independently in much the same fashion as other slime molds until food or water becomes unavailable. Interestingly, they then leave a chemical trail that acts like a pheromone to attract other cellular slime mold cells to a central location, where they form a pseudoplasmodium. During this stage, the individual cells, by still unknown means, communicate and coordinate their movements to act as one large blob. As the pseudoplasmodium moves, it can divide and (in unfavorable conditions, such as high heat or excessive dryness) form fungi-like fruiting bodies that develop haploid spores. The haploid spores remain dormant until favorable conditions return, at which time they grow into individual haploid slime molds.
Myxomycota Acellular slime molds, Myxomycota, are unique in producing structures called plasmodia, which appear to be a mass of cells, but in reality are one large cell that contains many nuclei free to float unhindered by internal membrane barriers. The plasmodium slime mold remains in this blob stage feeding on bacteria, fungi, and other organic nutrients, typically found on the floor of a deciduous forest, because of its mobility. In its blob form, it also has greater surface area to transfer materials to and from the environment. However, when food or water is scarce or the environment becomes too dry, the plasmodium transfigures into the moldlike mass and produces the characteristic fungilike fruiting bodies. The fruiting bodies create haploid spores via meiosis, which then combine to become diploid and begin growing into amoebalike blobs when conditions again become favorable.
Slime Molds Continued Although slime molds do not cause any type of diseases, they can be very alarming to find in your backyard. Slime molds often kill gardens by consuming their nutrients. Slime molds are important in labs, since they are not difficult to grow, they are inexpensive, and they are very complex.
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