Protists Lecture Notes PDF

Protists Concepts: 28.1-28.5 Campbell. Biology. 3rd ed. Outline 1. Introduction to Protists 2. Four Supergroups and their Members 3. Unresolved Protists 4. Human and Ecological Relevance http://www.hawaii.edu/reefalgae/publications/ediblelimu 1. Introduction to Protists • Domain Eukarya - All m...

Protists Concepts: 28.1-28.5 Campbell. Biology. 3rd ed. Outline 1. Introduction to Protists 2. Four Supergroups and their Members 3. Unresolved Protists 4. Human and Ecological Relevance http://www.hawaii.edu/reefalgae/publications/ediblelimu 1. Introduction to Protists • Domain Eukarya - All members have eukaryotic cells. • Nucleus, membrane bound organelles, DNA linear • Includes Kingdoms: Protista, Plantae, Fungi, Animalia • Organisms in Protista are diverse and heterogeneous. • Nutrition varied: photosynthetic, ingestion of food, absorption of food • Individual life cycles vary considerably. • Reproduction generally by cell division (meiosis) and sexual processes (fertilization). Some protists are asexual. • Algae are in Kingdom Protista. • Grouped into several phyla based on form of reproductive cells, and combinations of pigments and food reserves. Endosymbiosis and Eukaryote Evolution • Protist diversity is attributed to endosymbiosis which is relationship between two species where one organism lives inside the cell or cells of the other organism • eukaryote host cell engulfed a bacterium that later became mitochondria organelle in eukaryotes • photosynthesis attributed to non-photosynthetic eukaryote cell engulfed cyanobacterium that later became chloroplast organelle in eukaryotes • Both of the above examples are referred to as Primary Endosymbiosis • Mitochondria and chloroplasts passed down to successive eukaryotic generations is referred to as Secondary Endosymbiosis 2. Four Supergroups and their Members • Phylogeny of Protists and current hypothesis is Four Supergroups • Excavata • SAR • Archaeplastida • Unikonta Figure 28.2 Exploring Protistan Diversity Supergroup proposed based on cytoskeleton morphology Named for their characteristic "excavated" feeding groove Includes autotrophs, heterotrophs and parasites This supergroup known for modified mitochondria and unique flagella • Clade Diplomonads and Clade Parabasalids • Have modified mitochondria • Mostly found in anaerobic environments • Many parasites in this group eg Gardia intestinalis • Multiple flagella • • • • • Clade Euglenozoans • Distinguishing feature is the presence of a rod with a spiral or crystalline structure inside each flagella https://biology-forums.com/index.php?action=gallery;sa=view;id=768#images Excavata Supergroup Figure 28.6 Euglenozoan flagellum SAR Supergroup • Supergroup proposed based on whole genome DNA sequence analyses • Large, diverse set of protists in this group. • Lacks a formal name due to controversy among scientists with respect to this group • Includes three clades: Stramenopiles, Alveolates and Rhizarians • Clade Stramenopiles • Name (latin for straw) refers to their characteristic flagellum which has many fine, hairlike projections. Secondary flagella is smooth • This group includes diatoms, brown algae, oomycetes (water molds) • Diatoms • Unicellular • Diverse group, over 100,000 species • Major component of phytoplankton (ie, photosynthetic) • Diatomaceous earth (diatom cell walls) • Made of hydrated silica • Effective against predation • Some diatoms produce toxins, harmful to humans • Diatom blooms may help to reduce C02 levels and store carbon in their bodies for many years before reaching the ocean floor and decomposing Figure 28.10 The diatom Triceratium morlandii The cell wall is composed of two parts that overlap like a shoe box with a lid • Brown algae • Largest and most complex algae • All multicellular, mostly marine in cold water • Color is due to carotenoids (fucoxanthin) in their plastids . A photosynthetic pigment • Some have specialized tissues (similar to plants) such as holdfast, which anchors the alga and a stemlike stipe which supports the leaflike blades • Food source for humans and substance (algin) found in cell walls functions as a thickening agent in processed foods such as pudding or salad dressing Alternation of Generations • Laminaria provides an example of the Alternation of Generations in multicellular brown algae. Diploid = sporophyte Haploid = gametophyte Laminaria is heteromorphic = sporophyte and gametophyte are structurally different • Oomycetes (water molds and their relatives) • Water molds and mildews • Multicellular filaments (hyphae) that resemble fungal hyphae. Sometimes referred to as "fungal-like protists" • Contain cellulose in their cell walls (fungi contain chitin in cell walls) • Mainly decomposers or parasites • White rust and downy mildew plant parasites • One of the most important oomycete plant pathogens is a water mold Phytophthora infestans • Causal agent of Late Blight of Potato • Contributed to the Irish Potato Famine in the 1800s in which over 1 million people died and many more were forced to leave Ireland • Common place organism in much of the world • Clade Alveolates • Abundant in many habitats and include autotrophs and heterotrophs • Have membrane bound sacs (alveoli) under the plasma membrane • Function unknown to scientists but hypothesize they help stabilize the cell surface or regulate cell water and ion content • Include dinoflagellates, apicomplexans and ciliates • Dinoflagellates • Red tides – coastal waters appear red following blooms due to presence of carotenoid pigments located in plastids • Marine and fresh water • Single celled • Two flagella • Sudden multiplication • Toxins produced by certain dinoflagellates cause massive kills of invertebrates and fish. Humans can also be fatally affected by eating molluscs that have accumulated the toxins • Clade Rhizarians • This group includes many species of Amoebas, protists that move by way of a pseudopodia (extensions of the cytoplasm) which serves as an anchor or "false feet" • Amoebas that are Rhizarians differ from other amoebas in that they have threadlike pseudopodia. • Other protists in this group (non-amoeboid) are flagellated and feed using a threadlike pseudopodia (vs flat, broad or bulbous) Amoeba https://www.daviddarling.info/encyclopedia/P/pseudopodium.html Archaeplastida Supergroup • Red algae, green algae and land plants make up this eukaryotic supergroup • All descendants of an ancient protist that engulfed a cyanobacterium • Photoautotrophic • Red Algae • Rhodophytes, from the Greek rhodos, red) are reddish in color owing to the photosynthetic pigment phycoerythrin. • Found in warm, coastal waters • Most are multicellular and exhibit alternation of generations • Lack a flagellated stage and rely on gametes to be brought together by water currents • Numbers of species produce agar. Some species are a human food source eg. Porphyra (Japanese "nori") • Green algae • Closely related to land plants (confirmed with molecular and cellular data) • Chloroplasts of green algae similar in structure and pigment composition (chlorophyll a ) to land plants • Unicellular, filamentous, platelike colonies, netlike tubes, hollow spheres, lettuce-like leaves • Two main groups of green algae • Charophytes and Chlorophytes • Charophytes more closely related to plants • Most chlorophytes have complex life cycles with both asexual and sexual reproduction • Some species exhibit alternation of generations Chlorophytes • Live in various aquatic environments as phytoplankton or in damp soil • Some even live in snow and carry out photosynthesis successfully • Snow acts as a shield • specialized pigments in the cytoplasm that are red in color create red streaks in the snow (as seen in the mountains of British Columbia) https://en.wikipedia.org/wiki/Watermelon_snow Chlorophyta (green algae) • Chlamydomonas (a genus of green algae) • Common inhabitant of freshwater pools • Unicellular • Pair of whip-like flagella on one end. • Two or more vacuoles at base of flagella – Regulate water content of cell and remove waste • Single, cup-shaped chloroplast with one or two pyrenoids inside – Pyrenoids - Proteinaceous structures associated with synthesis of starch • Red eyespot near base of flagella – Allows alga to swim toward light Unikonta Supergroup • Very diverse supergroup of eukaryotes which includes animals, fungi and protists • Two major clades (determined through molecular systematics) • Clade Amoebozoans – includes slime molds, tubulinids and entameobas • Clade Opisthokonts - includes fungi and nucleariids; animals and choanoflagellates • Clade Ameobozoans • Many species of amoebas with lobe or tube-shaped pseudopodia (contrast to threadlike pseudopodia in SAR supergroup: Rhizarian) • Includes slime molds, tubulinids and entamoebas https://www.chegg.com/learn/biology/introduction-to -biology/amoebas-amoebozoa#shape-of-amoeba: Slime molds • Previously thought to be fungi because similar fruiting body structures • Molecular systematics suggests they descended from unicellular ancestors • Two main branches of slime molds: plasmodial and cellular slime molds • Plasmodial Slime Molds • During one stage of life cycle they form a mass called a plasmodium (multinucleate) • Not multicellular – Protoplasm containing many diploid nuclei – No cell wall • This plasmodium "supercell" extends pseudopodia through the soils or leaf mulch and engulfs food through phagocytosis (uses plasma membrane to engulf particles) Plasmodium • Cellular slime mold • Individual cells feed independently, dividing and producing separate new cells periodically. • Clump together to form mass called pseudoplasmodium during periods when food sources are low • Although clumped together, cells remain separated by their individual plasma membranes https://uwm.edu/field-station/and-now-for-something-a-little-different-slime-molds/ 3. Unresolved Protists • Molecular data (DNA/RNA) is hard to obtain for some organisms due to difficulty to isolate and culture • Many unresolved groups in the eukaryotic tree including haptophytes and cryptomonads 4. Human and Ecological Relevance • Diatoms • Oils are sources of vitamins. • Diatomaceous earth (made from diatoms) • Filtration • Polishes, toothpaste • Paint that reflects light • Other algae • Chlorella • Potential human food source Human and Ecological Relevance • Algin • Produced by giant kelps (seaweeds) and other brown algae • Ice cream, salad dressing • Latex paint, textiles, ceramics • Regulates water behavior • Controls development of ice crystals • Regulates penetration of water • Stabilizes suspensions Vessel harvesting kelp Human and Ecological Relevance • Minerals and food • Iodine from kelp (seaweeds: the brown algae) • Red algae • Food - Dulse, nori • Carrageenan (polysaccharides)- Thickening agent (food) • Agar • Produced by red alga Gelidium • Solidifier of nutrient culture media • Retains moistness in bakery products • Base for cosmetics The End THANK YOU QUESTIONS? HAVE A WONDERFUL DAY!