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The Protists

The Protists. Chapter 21. Protists. General characteristics Unicellular, colonial, simple multicellular organisms Eukaryotic Some exhibit both plant and animal characteristics Euglenoids Slime molds. Protists. Many are photosynthetic All have chlorophyll a Often called algae.

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The Protists

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  1. The Protists Chapter 21

  2. Protists • General characteristics • Unicellular, colonial, simple multicellular organisms • Eukaryotic • Some exhibit both plant and animal characteristics • Euglenoids • Slime molds

  3. Protists • Many are photosynthetic • All have chlorophyll a • Often called algae

  4. Protists • Evolutionary relationships of eukaryotes • Difficult problem • Splits between many lineages of eukaryotes are ancient • Have been events in which organisms (or parts of organisms) that are not closely related have joined to form new organisms • Not many characters are shared by all members of group • Shared characters often yield different results when analyzed cladistically

  5. Protists • At base of eukaryotic tree • Group of protists • Some lack mitochondria and live as parasites on other organisms • Rest of eukaryotes divided into two major clades • One clade • Animals, fungi, slime molds, and small group of amoeboid organisms • None are photosynthetic • Most are motile (except fungi)

  6. Protists • Other clade • Variety of protist groups • Includes both photosynthetic and nonphotosynthetic protists

  7. Photosynthetic Protists • Commonly called algae • Variety of life histories, body forms, ecological roles • Often named for distinctive colors • Unicellular, colonial, filamentous, sheetlike

  8. Amoebozoa • Clade of protists that includes amoebas and slime molds • Traits combine aspects of fungi and animals • Animal characteristics • Lack cell walls, engulf food, have motile cells at some phase of life cycle • Fungi and plant characteristics • Form sporangia and nonmotile cells with cell walls

  9. Amoebozoa • Two groups of slime molds • Myxomycota • Acrasiomycota

  10. Alveolates • Common character • System of alveoli • Tiny membrane-enclosed sacs found beneath plasma membrane • Clade composed of four ecologically and economically significant lineages • Ciliates • Found in freshwater • Have cilia and engulf food • Often called protozoa • Example: Paramecium

  11. Alveolates • Foraminifera • Characterized by hard shell • Feeding strategies include active predation, scavenging, using sticky webs to trap food • Shells • Common fossils • Important in dating geological strata and in oil exploration

  12. Alveolates • Apicomplexa • Parasitic or pathogenic protists • Found to contain vestigial plastids • Examples • Plasmodium (causes malaria) • Toxoplasma (causes toxoplasmosis)

  13. Alveolates • Photosynthetic dinoflagellates • Most are unicellular, motile, and marine • Usually have two flagella (both emerge from same pore) • One is flat and ribbonlike, encircles cell in groove around middle, provides rotational movement • Other flagellum trails behind and provides forward movement • Contain pigments • Chlorophylls a and c • Brown pigment (fucoxanthin)

  14. Alveolates • Chloroplasts surrounded by three or four membranes • May also contain a remnant nucleus • Some are bioluminescent • Overgrowth (bloom) can cause red tide

  15. Euglenoids • Typically single-celled • Usually in freshwater but could be in salt or brackish water or soil • A few are parasitic • Lack cell wall • Flexible strips of proteins and microtubules under cell membrane • Have two flagella

  16. Euglenoids • About one third of the 1,000 species have chloroplasts • Contain chlorophylls a and b, carotenoids • Three membranes around chloroplasts • May have eyespot • Red or orange light-sensitive organelle • Pigment (astaxanthin) is a carotenoid has antioxidant properties • Extracted and sold as health supplement

  17. Euglenoids • Never been observed to reproduce sexually • Important in food chains of freshwater ecosystems • Ecological indicators of water that is rich in organic matter

  18. Heterokonts • Clade also sometimes called Stramenopiles or Chromista • All have two unequally sized flagella • Heterokonts and alveolates share common ancestor

  19. Heterokonts • Includes • Oomycota (water molds and downy mildew) • Xanthophyta (golden algae) • Chrysophyta (golden algae) • Diatoms • Brown algae

  20. Heterokonts

  21. Heterokonts • Oomycota • Includes egg fungi, downy mildews, and water molds • Fungal characteristics • Hyphae, produce spores, lack chlorophyll • Algal characteristics • Cellulose cell walls, swimming spores, some cellular details, some metabolic pathways

  22. Heterokonts • Oomycota • Most are decomposers • Some are pathogens of important crops • Downy mildew of grapes • Plasmopora viticola • Nearly destroyed French vineyards in nineteenth century • Potato blight • Phytophthora infestans • Changed history of Ireland in 1840s

  23. Heterokonts • Diatoms • Important members of phytoplankton • Cell wall made out of silica • Two parts (valves) to cell wall • Fit together like halves of Petri dish • Shape of cell varies • Pigments • Chlorophylls a and c • Fucoxanthin

  24. Heterokonts • Diatoms • Store food reserves as oil • Some exhibit gliding motion • Stalked diatoms grow as epiphytes on seaweeds and kelps • Can also become attached to nonliving surfaces • Create algal turfs • Coat shallow rocks in quiet freshwater or marine habitats • Have as high a daily productivity per square meter as tropical rain forest

  25. Heterokonts • Diatoms • Dominate surfaces of salt mudflats • Extensive fossil record • Indicators for petroleum exploration • Silica shells form extensive deposits

  26. Heterokonts • Brown algae • Almost exclusively marine • More abundant in cool, shallow waters • More complex brown algae  kelps • Chlorophylls a and c, fucoxanthin • No grana in chloroplasts • Store carbohydrates as mannitol or laminaran • Cell walls composed of cellulose and alginates

  27. Heterokonts • Brown algae • Kelps • Example • Macrocystis • Largest known kelp • Fast growth rate • Consists of • Holdfast – anchors • Stipes – stem-like structure • Blades – leaf-like • Gas-filled air bladder - buoyancy

  28. Heterokonts • Brown algae • Kelps • Outer layer is protective and consists of cells that are also meristematic and contain chloroplasts  called meristoderm • Region of cortex beneath meristoderm • Composed of parenchyma-like cells • Mucilage-secreting cells line canals through medulla • Medulla • Innermost part of stipe • Loosely packed filaments of cells

  29. Heterokonts • Brown algae • Kelps • Cells that function as sieve elements • Found in transition zone between cortex and medulla • Have sieve plates, form callose, adjoin one another to make continuous tubes • Mannitol moves through tubes • No tissue that resembles xylem

  30. The Plants • Molecular data supports idea that red algae, green algae, and land plants belong in same clade • Green algae • Not a natural monophyletic group • Gave rise to land plants

  31. The Plants • Red algae • Almost exclusively marine • Most abundant in warm water • Can grow to considerable depth • More complex forms called seaweeds • Parenchyma-like tissue • Holdfast for anchoring • Stipes never very long • Blades never have gas bladders

  32. The Plants • Red algae • Pigments • Chlorophyll a and phycobilins • Cell wall • Cellulose and sometimes agar or carrageenan • Food storage molecule • Floridean starch

  33. Comparison of Red and Brown Algae

  34. The Plants • Green algae • Mainly in freshwater habitats but could be in saltwater, on snow, in hot springs, on soil, on leaves and branches of terrestrial plants • Shared characteristics • Chlorophylls a and b, carotenoid accessory pigments • Food stored as starch • Cellulose cell walls • Formation of phragmoplast during mitosis • Asymmetrically attached flagella

  35. The Plants • Green algae • Groups • Chlorophyceae • Ulvophyceae • Charophytes

  36. The Plants • Green algae • Chlorophyceae • Two flagella at anterior end • Single, large, cup-shaped chloroplast • Most have red-colored carotene eyespot • Examples • Gonium • Volvox

  37. The Plants • Green algae • Ulvophyceae • Sea lettuces • Typically small, green seaweeds • Consumed as food in many places • Example • Caulerpa • Accidentally spread to areas with no natural limits to growth • Multiplied explosively • Produces toxins that are lethal to urchins and some fish • Has been discovered off coast of California

  38. The Plants • Green algae • Charophytes • Group of ancient green algae • Examples • Coleochaete • Once thought to be closest living relative to land plants • Chara • According to molecular characters → more closely related to land plants than Coleochaete

  39. Ecological and Economic Importance of Algae • Phytoplankton • Base of aquatic food chains • “grasses of the sea” • Unicellular • Produce about four times the amount of photosynthate that is produced by the Earth’s croplands each year • Bloom • Algal overgrowth

  40. Ecological and Economic Importance of Algae • Help build tropical reefs • Coralline algae • Certain red and green algae • Create carbonate exoskeleton that becomes part of reef when alga die

  41. Ecological and Economic Importance of Algae • Coralline algae • Some algae grow symbiotically with coralline animals • Mutualistic relationship • Algae produces sugar and oxygen for animal • Cells of coral contribute CO2, nitrogen, and minerals for alga • Usually dinoflagellate Symbiodinium microadriaticum • Has photosynthetic rate 10 times greater than phytoplankton • Protected and nourished by animal cytoplasm around it

  42. Ecological and Economic Importance of Algae • Medicine, food, and fertilizer • Laminaria • Harvested off coast of China as source of iodine • Porphyra (nori) • Cultivated • Supplement to Japanese diet • limu • used as food source by Polynesians in Hawaii

  43. Ecological and Economic Importance of Algae • Medicine, food, and fertilizer • Palmaria palmate • red seaweed, dulce • Used as food in British isles • Chondrus crispus • Irish moss, red algae • Used to make jelly desert called blancmange

  44. Ecological and Economic Importance of Algae • Medicine, food, and fertilizer • Good fertilizer or cattle feed supplements • Compares favorably with manure as a fertilizer • Enhances germination • Increases uptake of nutrients • Seems to give degree of resistance to frost, pathogens, and insects

  45. Ecological and Economic Importance of Algae • Uses of algal cell walls • Diatomite (diatomaceous earth) • Rich deposit near Lompoc, California • Uses of diatomite • Superior filter or clarifying material • Added to many materials to provide bulk, improve flow, increase stability • Dental impressions, grouting, paint, asphalt, pesticides • Abrasive

  46. Ecological and Economic Importance of Algae • Uses of algal cell walls • Agar • Primarily obtained from red algae, Gelidium and Gracilaria • Used as a culture medium • Substance purified from agar (agarose) used for gel electrophoresis • Used in baking industry • Added to icing to retard drying in open air or melting in cellophane packages • Used as a bulk laxative

  47. Ecological and Economic Importance of Algae • Uses of algal cell walls • Carrageenan • Reacts with proteins in milk to make stable, creamy, thick solution or gel • Used commercially in ice cream, whipped cream, fruit syrups, chocolate milk, custard, evaporated milk, bread, macaroni • Added to dietetic, low-calorie foods • Used in toothpaste, pharmaceutical jellies, and lotions • Mainly comes from Irish moss, red algae

  48. Ecological and Economic Importance of Algae • Uses of algal cell walls • Algin • Compound of brown algae • Strongly absorbs water • Used as an additive to beer, water-based paints, textile sizing, ceramic glaze, syrup, toothpaste, hand lotion

  49. Ecological and Economic Importance of Algae • Algin • Commercially harvested species • Macrocystis pyrifera – along California coast • Ascophyllum, Fucus, and Laminaria – off Maritime Canada, northeastern United States, England, China coast • Durvillea – from Australian waters

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