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Information about Protista

Published on March 26, 2008

Author: Flemel


PROTISTA:  PROTISTA O2 ACCUMULATION:  O2 ACCUMULATION Oxygenic photosynthesis arose in prokaryotes ~2.5 billion years ago The earth’s atmosphere was radically changed O2 was toxic to cells Energy-rich organic molecules no longer accumulated Biotically produced organic molecules became the primary source of energy and carbon RAPID EVOLUTION:  RAPID EVOLUTION Rapid evolutionary change typically follows major environmental changes “Punctuated equilibrium” A tolerance to O2 arose in many populations The ability to use O2 metabolically quickly followed in many of these groups New ways arose to acquire & use organic molecules Various species interactions arose Symbiosis, predation Early eukaryotic cells arose EARLY EUKARYOTES:  EARLY EUKARYOTES The earliest eukaryotes were protists >2.1 billion years ago Significantly different from their prokaryotic ancestors e.g., Membrane-bound nucleus containing DNA associated with histone proteins e.g., Mitochondria and sometimes chloroplasts e.g., Other internal membrane-bound organelles e.g., Mitotic (and eventually meiotic) cell division PROTISTS:  PROTISTS Very diverse group >60,000 known species Most are unicellular Some are colonial Some are multicellular Not “simple” at the cellular level Remember, a unicellular organism must carry out all basic functions of life within a single cell Cells within a multicellular organism can become specialized, and need not carry out all such functions NUTRITION:  NUTRITION Protists are the most nutritionally diverse eukaryotic group Most are aerobic, and possess mitochondria Some lack mitochondria and live in anaerobic environments Some lack mitochondria, but possess mutualistic, respiring bacteria NUTRITION:  NUTRITION Protists are the most nutritionally diverse eukaryotic group Some are photoautotrophs Some are chemoheterotrophs Some are both photoautotrophs and chemoheterotrophs KINGDOM PROTISTA:  KINGDOM PROTISTA The traditional Kingdom Protista does not represent a monophyletic group Multiple monophyletic lineages are grouped These groups should represent separate kingdoms Exactly how to divide Kingdom Protista into multiple kingdoms is not entirely clear MAJOR PROTISTAN GROUPS:  MAJOR PROTISTAN GROUPS branch leading to plants brown algae chrysophytes oomycotes Stramenopiles charophytes green algae red algae slime molds parabasalids (e.g., Trichomonas) diplomonads (e.g., Giardia) Endosymbiotic origins from prokaryotic ancestors amoeboid protozoans “crown” of eukaryotes (rapid divergences) branch leading to fungi branch leading to animals Alveolates ciliates sporozoans dinoflagellates euglenoids kinetoplastids ? MAJOR PROTISTAN GROUPS:  MAJOR PROTISTAN GROUPS MONOPHYLETIC GROUPS:  MONOPHYLETIC GROUPS We will discuss several monophyletic groups Ancient flagellates Flagellated protozoans Amoeboid protozoans Alveolates Stramenophiles Plant lineage Slime molds ANCIENT FLAGELLATES:  ANCIENT FLAGELLATES Parabasilids and Diplomonads Free-living predatory and parasitic cells Some possess both flagella and pseudopods Evolutionary link with amoebae? ANCIENT FLAGELLATES:  ANCIENT FLAGELLATES Parabasilids e.g., Trichomonas vaginalis, a trichomonad Sexually transmitted A causative agent of vaginitis Swelling, itching, burning Can damage urinary and reproductive tracts ANCIENT FLAGELLATES:  ANCIENT FLAGELLATES Diplomonads e.g., Giardia lamblia Internal parasite of various animals e.g., humans, cattle, beavers, etc. >20% of human population infected at any given time Fecal-oral infection route Encysted cells shed in feces Infection via feces-contaminated water Often causes only mild intestinal upsets Can cause severe gastroenteritis “Girardiasis” FLAGELLATED PROTOZOANS:  FLAGELLATED PROTOZOANS Euglenoids & Kinetoplastids Possess one or more flagella All are heterotrophic FLAGELLATED PROTOZOANS:  FLAGELLATED PROTOZOANS Euglenoids >1,000 species Free-living, flagellated cells Most are photoautotrophs Chloroplasts with chlorophylls a & b (Just like plants) Arose in parallel to chloroplasts in green algae Some are chemoheterotrophs Possess a pellicle Flexible, protein-rich cell covering FLAGELLATED PROTOZOANS:  FLAGELLATED PROTOZOANS Kinetoplastids e.g., Trypanosoma brucei Causative agent of African sleeping sickness Neurological disease Transmission vector is tsetse fly AMOEBOID PROTOZOANS:  AMOEBOID PROTOZOANS “Sarcodina” Ancestors lost their permanent motile structures Move by pseudopod formation/cytoplasmic streaming Various groups Rhizopods Naked amoebas & foraminiferans Actinopods Radiolarans & heliozoans AMOEBOID PROTOZOANS:  AMOEBOID PROTOZOANS Rhozopods: Naked Amoebas Found in damp soil, saltwater, fresh water Cytoskeletal elements change continually Most are free-living phagocytes Engulf other protozoans & bacteria Some are opportunistic parasites AMOEBOID PROTOZOANS:  AMOEBOID PROTOZOANS Rhizopods: Foraminiferans Most live on the seafloor Perforated external shell Contains calcium carbonate Mucus-covered pseudopods extend through perforations Most named species (99%) are extinct Fossilized remains mined for chalk, cement AMOEBOID PROTOZOANS:  AMOEBOID PROTOZOANS Actinopods: Radiolarans Numerous in fossil record Silica-hardened parts Components of plankton Drifting aquatic communities Some species form colonies AMOEBOID PROTOZOANS:  AMOEBOID PROTOZOANS Actinopods: Heliozoans Pseudopods radiate like sun’s rays “Sun animals” Vacuoles impart buoyancy ALVEOLATES:  ALVEOLATES Possess tiny membrane-bound sacs (alveoli) beneath outer membrane May stabilize cell surface Three groups Ciliates Sporozoans Dinoflagellates CILIATES:  CILIATES e.g., Paramecium Many possess numerous cilia Motile structures Beat in synchronized fashion Prey on bacteria, algae, each other ~65% are free-living and motile Others attach to some substrate Some form colonies ~30% are symbionts CILIATES:  CILIATES Reproduce sexually and asexually Similar to most protozoans in this regard Asexual process is “binary fission” Not to be confused with prokaryotic fission Sexual process is “conjugation” Not to be confused with bacterial conjugation CONJUGATION:  CONJUGATION CONJUGATION:  CONJUGATION SPOROZOANS :  SPOROZOANS Parasitic alveolates completing a portion of their life cycle within specific host cells Form motile infective cells (“sporozoites”) Many cause serious diseases e.g., Cryptosporidium  cryptosporidiosis e.g., Pneumocystis carinii  pneumonia Common secondary infection in AIDS patients e.g., Toxoplasma  toxoplasmosis Cat  human e.g., Plasmodium  malaria MALARIA:  MALARIA Caused by 4 different species of Plasmodium Has infected > 100 million people ~1 million die yearly in Africa alone Shaking, chills, fever, sweats Symptoms subside, but can reoccur Transmitted to humans by mosquitoes Females of genus Anopheles MALARIA:  MALARIA Salivary gland  blood delivery of sporozoites Sporozoites travel to liver Asexual reproduction produces merozoites Some merozoites divide mitotically in RBCs Other merozoites develop into gametocytes Male and female gametocytes develop into gametes Occurs within mosquito, not human (too warm, O2 poor) Gametes fuse to form zygotes Zygotes divide to form sporozoites PLASMODIUM LIFE CYCLE:  PLASMODIUM LIFE CYCLE PLASMODIUM LIFE CYCLE:  PLASMODIUM LIFE CYCLE MALARIA:  MALARIA Malaria has been and still is prevalent in portions of Africa, Asia, and the Middle East Malaria has infected > 100 million people ~1 million die yearly in Africa alone SICKLE-CELL ANEMIA:  SICKLE-CELL ANEMIA The prevalence of sickle-cell anemia roughly parallels that of malaria Is there a connection? SICKLE-CELL ANEMIA:  SICKLE-CELL ANEMIA Genetically determined Aberrant b-globin allele (HbS) Glutamic acid (HbA)  valine (HbS) Cells sickle under low oxygen conditions Multiple deleterious effects SICKLE-CELL ANEMIA:  SICKLE-CELL ANEMIA SLAVE TRADE:  SLAVE TRADE Many of the African slaves transported to the Americas came from regions where malaria and sickle-cell anemia were prevalent As a result, 0.25% of African-Americans have sickle-cell anemia 10% are carriers of the sickle-cell allele SICKLE-CELL ANEMIA:  SICKLE-CELL ANEMIA If the HbS allele is bad, why is its frequency so high in certain populations? Shouldn’t natural selection weed it out? SICKLE-CELL ANEMIA:  SICKLE-CELL ANEMIA Though having sickle-cell anemia is harmful, possession of a single HbS allele is beneficial Individuals possessing a single HbS allele possess an innate resistance to the malaria parasite Thus, natural selection preserves this allele in populations due to this beneficial effect How does this work? SSA & MALARIA:  SSA & MALARIA HbS/HbS individuals have sickle-cell anemia HbA/HbS individuals are only mildly anemic HbA/HbA individuals are “normal” Who gets killed by sickle-cell anemia? Who gets killed by malaria? DINOFLAGELLATES:  DINOFLAGELLATES Pyrrhophyta, another branch of alveolates > 1,200 species Most are unicellular and photosynthetic Some are symbionts with coral Two flagella One occupies groove around cell body Cellulose plates surround body Yellow-green, green, blue, brown, or red Different pigments DINOFLAGELLATES:  DINOFLAGELLATES Dinoflagellates periodically experience huge increases in population size “Algal blooms” cause “red tides” Toxins produced by dinoflagellates accumulate Toxins kill fish feeding on these phytoplankton Birds feeding on such fish can die Humans feeding on shellfish having eaten these dinoflagellates can experience “paralytic shellfish poisoning” STRAMENOPHILES:  STRAMENOPHILES Three groups Oomycotes Chrysophytes Brown algae Possess two flagella One has thin filaments projecting from it and resembles a feather OOMYCOTES:  OOMYCOTES Ancient stramenophiles Main groups Water molds Downy mildews & white rusts OOMYCOTES:  OOMYCOTES Water Molds ~580 known species Non-photosynthetic Saprobic decomposers of aquatic habitats Some are parasites e.g., Saprolegnia commonly attacks damaged tissue in aquarium fish OOMYCOTES:  OOMYCOTES Downy Mildews Non-photosynthetic major pathogens e.g., Plasmopara viticola molds grapevines & fruits e.g., Phytophthora infestans caused the Irish potato blight 1/3 of Irish population lost from 1845 – 1860 Starvation Cholera Emigration CHRYSOPHYTES:  CHRYSOPHYTES One photosynthetic group of stramenophiles Possess chlorophylls a, c1, and c2 Most are free-living Various groups Golden algae Yellow-green algae Diatoms Coccolithophores CHRYSOPHYTES:  CHRYSOPHYTES Golden Algae ~500 known species Covered by silica scales or other hard parts Possess accessory pigment fucoxanthin Golden-brown pigment Can form colonies in phytoplankton Some species resemble true amoebas (With chloroplasts) CHRYSOPHYTES:  CHRYSOPHYTES Yellow-green Algae ~600 known species Common components of aquatic phytoplankton Can form colonies Lack fucoxanthin Golden-brown carotenoid pigment Most are non-motile All produce flagellated gametes CHRYSOPHYTES:  CHRYSOPHYTES Diatoms ~5,600 species currently exist ~35,000 extinct species Possess a silica shell Two parts overlap like a Petri plate Very diverse shapes Finely crushed shells accumulate at the bottom of lakes and seas Used as fine abrasives, filters, and insulation CHRYSOPHYTES:  CHRYSOPHYTES Coccolithophores ~500 species currently exist Most are unicellular marine organisms Protected by calcium carbonate plates Accumulations of plates helped form marine sediments, chalk and limestone deposits Mucus around cells can clog fish gills during algal blooms BROWN ALGAE:  BROWN ALGAE Another group of photosynthetic stramenophiles ~1,500 species currently exist Most live in cool or temperate seawater Possess chlorophylls a, c1, and c2 Possess fucoxanthin and/or other accessory pigments Appear olive-green, golden, dark brown, etc. Microscopic to very macroscopic Diverse life cycles Asexual and sexual phases BROWN ALGAE:  BROWN ALGAE Giant kelps are largest, most complex protistans Complex multicelled sporophytes Stipes (stemlike parts) Blades (leaflike parts) Holdfasts (anchoring structures) Buoyancy provided by hollow, gas-filled bladders Why do you think this is important? Tubelike arrays in blades carry sugars to rest of body Evolved in parallel in vascular plants BROWN ALGAE:  BROWN ALGAE Giant kelp beds function as productive ecosystems Homes to diverse bacteria, protozoans, animals Some species commercially harvested Food or fertilizer Extracts are components of ice cream, pudding, jelly beans, salad dressings, etc. Alginic acids from cell wall useful as a thickening agent PLANT LINEAGE:  PLANT LINEAGE The monophyletic group containing green algae and their closest relatives also contains plants These groups are sometimes classified in the plant kingdom Green algae (Chlorophyta) Zygophyta Charophyta Plants GREEN ALGAE:  GREEN ALGAE >7,000 known species Share many features with plants All are photosynthetic (oxygenic) Possess chlorophylls a & b Store carbohydrates as starch inside chloroplasts Some have cell walls composed of cellulose, pectins, and other polysaccharides Single-celled, sheetlike, tubular, or colonial Most are microscopic Generally possess two anterior flagella GREEN ALGAE:  GREEN ALGAE Most live in freshwater Some grow elsewhere Ocean surface Marine sediments Below soil surface On various substrates (rocks, snow, organisms, etc) Some are symbionts with fungi, protozoans, or marine animals GREEN ALGAE:  GREEN ALGAE Diverse modes of reproduction e.g., Chlamydomonas sexual & asexual cycles RED ALGAE (Rhodophyta):  RED ALGAE (Rhodophyta) ~4,100 species 95% saltwater / 5% freshwater Mucous material in cell wall imparts slippery texture Agar is made from cell wall extracts Culture media, cosmetics, jellies, etc. Nutritious food source Wrapping for sushi RED ALGAE (Rhodophyta):  RED ALGAE (Rhodophyta) Most abundant in tropical seas & warm currents Some grow at great depths Up to 265 meters in clear water Chlorophyll a plus accessory pigments Typically appear red, green, purple, or black Phycobilins are accessory pigments that absorb green and blue-green wavelengths that penetrate deep waters RED ALGAE (Rhodophyta):  RED ALGAE (Rhodophyta) Life cycles of most species include multicelled stages lacking tissues and organs Asexual and sexual phases in life cycle CHLOROPLASTS:  CHLOROPLASTS SLIME MOLDS:  SLIME MOLDS Free-living amoeba-like cells part of life cycle Two main types Cellular slime molds (Acrasiomycota) ~70 different species Plasmodial slime molds (Myxomycota) ~500 different species Predators Eat organic compounds and microorganisms Asexual reproduction involves colonies Sexual reproduction also exists SLIME MOLDS:  SLIME MOLDS CELLULAR SLIME MOLD LIFE CYCLE:  CELLULAR SLIME MOLD LIFE CYCLE PLASMODIAL SLIME MOLD LIFE CYCLE:  PLASMODIAL SLIME MOLD LIFE CYCLE

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