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Chapter 22

Chapter 22. Protists- The Simplest Eukaryotes. AP Biology Spring 2011. Objectives. Describe the criteria for the Kingdom Protista Describe the origin of the various protistans Tell how protists differ from bacteria Be able to compare protists with other eukaryotes

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Chapter 22

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  1. Chapter 22 Protists- The Simplest Eukaryotes AP Biology Spring 2011

  2. Objectives • Describe the criteria for the Kingdom Protista • Describe the origin of the various protistans • Tell how protists differ from bacteria • Be able to compare protists with other eukaryotes • Distinguish each of the major groups within the Protista

  3. Chapter 22.1 An Evolutionary Road Map

  4. Protists Characteristics • Protists: are the most like the first Eukaryotic cells • Have a nucleus • Most have mitochondria, ER, and Golgi bodies • Ribosomes are larger than bacteria’s • Have more than one chromosome, consisting of DNA with many proteins attached • Have cytoskeleton (microtubules) • Many have chloroplasts • Divide by mitosis, meiosis, or both • Eukaryotes

  5. Protists • A diverse group

  6. Protists Characteristics • Most single celled • There are colonial and multicelled species • Some: • Photoautotrophs • Preditors • Parasites • Decomposers • Many can form spores

  7. Protists- A Hodgepodge • A kingdom that represents an evolutionary crossroads between prokaryotes and “higher” forms of life • Recently the polyphyletic kingdom is being split into monophyletic groups • Fig. 22.2

  8. Protists- A Hodgepodge • The 7 monophyletic groups: • Diplomonads and Parabasalids • Kinetoplastids and Euglenoids • Foraminiferans and Radiolarians • Stramenopiles and Alveolates • Amoebozoans • Red Algae • Chlorophytes (green algae)

  9. Chapter 22.2-22.4 Basal Groups 22.2: Parabasalids and Diplomonads 22.3: Euglenoids and Kinetoplastids 22.4: Forams and Radiolarians

  10. 22.2 Parabasalids and Diplomonads • Most evolutionary distant groups • Consist of heterotrophic flagellates • Are sac like or elongated and live in many oxygen poor or anaerobic habitats • Have few mitochondria or none at all

  11. 22.2 Parabasalids and Diplomonads • Parabasalids: • Have equivalent of backbone • Bundled microtubules extending the length of the cell • Have flagella

  12. 22.2 Parabasalids and Diplomonads • Diplomonads: • Have 3 flagella at their anterior and and one at the trailing end • Girardia lamblia: • No lysosomes, mitochondria, or golgi bodies, does not form bipolar spindle at mitosis • This lineage may have started more than a billion years ago • Common intestinal parasite in humans and cattle • Anaerobic but can survive as cysts outside bodies • Cyst: resting stage with a covering of cell secretions

  13. Chapter 22.3 Euglenoids and Kinetoplastids • Flagellated • Single celled • Thickened flagellum reinforced along nearly all lengths by a crystalline rod-shaped structure

  14. Chapter 22.3 Euglenoids and Kinetoplastids • Euglenoids: • Free living cells of fresh water • 1/3 of modern species are heterotrophs, other 2/3 are photoautotrophs that acquired chloroplasts • Have a long and short flagellum • Long flagellum is thicker and stiffened by an adjoining rod

  15. Chapter 22.3 Euglenoids and Kinetoplastids • Eyespot: guides them toward light • Pellicle: flexible, translucent cover, made of protein rich material • Responsible for movement • Contractile Vacuole: • Euglenoid has a higher internal solute concentration • Counteracts water’s tendency to diffuse in • Reproduce by binary fission

  16. Chapter 22.3 Euglenoids and Kinetoplastids • Kinetoplastids: • Heterotrophic, colourless flagellates • Nearly all are parasites that can survive anaerobic and aerobic conditions • Large mass of mitochondrial DNA, used for adjusting mode of ATP formation under different conditions • Parasites Trypsanosoma, Leishmania (tropics), T. brucei (African sleeping sickness, tsetse fly is vector), T. cruzi (Chagas disease)

  17. 22.4 Forams and Radiolarians • Faraminiferans: • Start out in a one-chambered shell • As single celled heterotrophs increase in size, most add more chambers and occupy them • Psudopods interconnect • Probe water and spaces between sand grains for bacteria and other prey • Some harbor photosynthetic symbionts (dinoflagellates, golden alga, diatoms)

  18. 22.4 Forams and Radiolarians • Radiolarian: • Cell body has distinct outer zone with vacuoles that impart buoyancy and assist in prey capture and digestion • Outer perforated shell made of short silica rods • Most live in deep ocean water • Some part of marine plankton

  19. Chapter 22.5-22.7 The Alveolates 22.5:Ciliated Alveolates 22.6: Flagellated Alveolates 22.7: Malaria

  20. The Alveolates • Monophyletic group consisting of ciliates, dinoflagellates, apicomplexans • Have small membrane bound sacs beneath the plasma membrane (alveoli)

  21. 22.5 Ciliated Alveolates • Ciliates: • Live in seas and fresh water • Most free-living heterotrophs • 1/3 parasites or endosymbionts of animals • Few are colonial

  22. 22.5 Ciliated Alveolates • Cilia • Cover the surface of some species but are confined to specific regions on others • Beat in synchronized patterns • Moves body, directs food toward oral cavity

  23. 22.5 Ciliated Alveolates • Paramecium: • Cilia all over body surface • Gullet: starts at an oral depression • Cilia sweep food-laden water inside • Contractile vacuole: expel excess water from body • Pellicle: array of flattened sacs under plasma membrane • Store calcium ions which dictate ciliary beating • Trichocysts: bottle shaped capsules hold a long shaft with a barb at the tip • Defends against predetors

  24. 22.5 Ciliated Alveolates • Ciliates: • Reproduce both sexually and asexually • Micronucleus and macronucleus, both have to divide (not that efficient or effective) • Conjugation occurs between ciliates

  25. 22.6 Flagellated Alveolates • Dinoflagellates: • Live in freshwater and marine habitats • Half are heterotrophs, half are photoautotrophs • All deposit cellulose in their alveoli • Often thick enough to form armor plates in pellicle • Species that have thin deposits considered unarmored • Most have 2 flagella • Part of plankton • Can undergo algal blooms when abundant nutrients • Red tide: tint water red

  26. 22.6 Flagellated Alveolates • Apicomplexans: • Parasitic alveolates • Microtubular device that attaches to and pierces a host cell • Adults have no flagella or cilia but their gametes are flagellated • Ex. Plasmodium

  27. 22.7 Malaria • Malaria symptoms: • Start when liver cells rupture and release meroziotes, cellular debris, and metabolic wastes into blood • Shaking, chills, burning fever, sweats • After one episode will relapse weeks to months later • Later outcomes: jaundice, kidney failure, convulsions, coma

  28. 22.7 Malaria • Bite of female Anopheles mosquitos can transmit a motile infective stage to human hosts • Life cycle: • Sporozoite travels from mosquito to blood vessels to liver cells • Reproduces asexually by fission • Some offspring (meroziotes) reproduce asexually in RBC, which they rupture and kill • Other meroziotes develop into make and female gametocytes • Gametocytes do not mature into gametes until they enter the gut of another mosquito

  29. 22.7 Malaria • Plasmodium is the protist responsible • As of 2007, every 30 seconds one African child dies of malaria

  30. Chapter 22.8-22.9 The Stramenopiles 22.8: The (Mostly) Photosynthetic Stramenopliles 22.9: The Colourless Stramenopiles

  31. Stramenopiles • Have flagella that bristle with tinsel-like filaments • Single celled and multicelled • Most photosynthetic

  32. 22.8 The (Mostly) Photosynthetic Stramenopliles • Chrysophytes: • Free living photosynthetic cell with chloroplasts • Includes golden algae, yellow-green algae, coccolithophores, and diatoms

  33. 22.8 The (Mostly) Photosynthetic Stramenopliles • Golden algae: • Have covering of silica scales or other hard parts • Producers in many fresh water habitats • Yellow-brown because produce carotenoid fucoxanthin (masks chlorophylls)

  34. 22.8 The (Mostly) Photosynthetic Stramenopliles • Yellow-green algae: • Do not make fucoxanthin • Chlorophylls c gives yellowish-green colour • Common in salt marshes and freshwater habitats • Most immotile, gametes bear flagellum

  35. 22.8 The (Mostly) Photosynthetic Stramenopliles • Coccolithophores: • Parts of calcium carbonate form under plasma membrane of coccolithophores • Each year these cells die and sink to seafloor • Form calcium carbonate deposits • Deposits become part of limestone formations

  36. 22.8 The (Mostly) Photosynthetic Stramenopliles • Diatoms: • Have silica “shell” which has two perforated parts that overlap • Important primary producers, among fastest reproducers • Release free oxygen • Can convert bicarbonate back into carbon dioxide, makes them best at fixing carbon dioxide

  37. 22.8 The (Mostly) Photosynthetic Stramenopliles • Brown Algae: • Olive-green and brown seaweeds • Live in cool or temperate waters • Range from microscopic species to giant kelp • Diverse life cycles: sexual and asexual phases

  38. 22.9 The Colourless Stramenopiles • Oomycotes: (egg-fungi) • Once classified as fungi because have similar growth pattern and feed the same way • Spores give rise to a mesh of thin filaments that absorb nutrients from host tissues or decaying organic matter • Nuclei are diploid, not haploid as fungi • Cell wall has cellulose not chitin (fungi)

  39. 22.9 The Colourless Stramenopiles • Water molds: • Decomposers of aquatic habitats • Some parasites • Some aquatic, others ruin plants on land Water mold on dead larval mayfly

  40. 22.10-22.11 The Closest Relatives of Land Plants 22.10: Red Algae 22.11 Green Algae

  41. 22.10 Red Algae • Red Algae: • Most live in warm marine currents and clear tropical seas • Photoautotrophic algae: live in the deepest water • Hold phycobilins and chlorphyll a • Phycobilins are red accessory pigments • Endosymbiosis: chloroplasts of red algae may have evolved from ancient cyanobacteria

  42. 22.10 Red Algae • Most red algae show branching or sheet like patterns of multicellular growth • True tissues do not form • Life cycles diverse: asexual and sexual phases • Gametes are not flagellated

  43. 22.11 Green Algae • Green Algae: • Closest relative of land plants • Most green algae now classified as chlorophytes, other group called charophytes (more closely related to land plants, discussed in that section)

  44. 22.11 Green Algae • Green Algae (chlorophytes): • Chloroplasts contain chlorophylls a and b, store sugars as starch • Cellulose fibers strengthen the cell walls • Most aquatic • Sheetlike, filamentous, cuplike, and colonial types • Fig. 22.19 p. 364

  45. 22.12 Amoeboid Cells at the Crossroads

  46. Amoebozoa • Shape shifters • Werewolves? NOOOOOOOOOOO • Use cytoplasmic extensions to move • Most solitary cells, some display communal behavior and cell differentiation that relate to fungi and animals • Vast majority do not have cell walls, shell, or pellicle • Most form pseudopods

  47. Amoebas • Soft-bodied, free living cells that move on pseudopods • Often prey on bacteria, other protists, or tiny multicelled animals • Some parasitic: E.histolytica causes amoeba dysentery

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