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Chapter 28 Presentation

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Chapter 28 Presentation

  1. 1. Chapter 28 Protists
  2. 2. Overview: Living Small <ul><li>Even a low-power microscope can reveal a great variety of organisms in a drop of pond water </li></ul><ul><li>Protist is the informal name of the kingdom of mostly unicellular eukaryotes </li></ul><ul><li>Advances in eukaryotic systematics have caused the classification of protists to change significantly </li></ul><ul><li>Protists constitute a paraphyletic group, and Protista is no longer valid as a kingdom </li></ul>
  3. 3. Fig. 28-01 1 µm
  4. 4. Concept 28.1: Most eukaryotes are single-celled organisms <ul><li>Protists are eukaryotes and thus have organelles and are more complex than prokaryotes </li></ul><ul><li>Most protists are unicellular, but there are some colonial and multicellular species </li></ul>
  5. 5. Structural and Functional Diversity in Protists <ul><li>Protists exhibit more structural and functional diversity than any other group of eukaryotes </li></ul><ul><li>Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell </li></ul>
  6. 6. <ul><li>Protists, the most nutritionally diverse of all eukaryotes, include: </li></ul><ul><ul><li>Photoautotrophs, which contain chloroplasts </li></ul></ul><ul><ul><li>Heterotrophs, which absorb organic molecules or ingest larger food particles </li></ul></ul><ul><ul><li>Mixotrophs , which combine photosynthesis and heterotrophic nutrition </li></ul></ul>
  7. 7. <ul><li>Protists can reproduce asexually or sexually, or by the sexual processes of meiosis and syngamy </li></ul>
  8. 8. Endosymbiosis in Eukaryotic Evolution <ul><li>There is now considerable evidence that much protist diversity has its origins in endosymbiosis </li></ul><ul><li>Mitochondria evolved by endosymbiosis of an aerobic prokaryote </li></ul><ul><li>Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium </li></ul>
  9. 9. Fig. 28-02-1 1 µm Cyanobacterium Heterotrophic eukaryote Over the course of evolution, this membrane was lost. Red alga Green alga Primary endosymbiosis
  10. 10. Fig. 28-02-2 Cyanobacterium Heterotrophic eukaryote Over the course of evolution, this membrane was lost. Red alga Green alga Primary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Stramenopiles Plastid Euglenids Chlorarachniophytes
  11. 11. <ul><li>The plastid-bearing lineage of protists evolved into red algae and green algae </li></ul><ul><li>On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis , in which they were ingested by a heterotrophic eukaryote </li></ul>
  12. 12. Five Supergroups of Eukaryotes <ul><li>It is no longer thought that amitochondriates (lacking mitochondria) are the oldest lineage of eukaryotes </li></ul><ul><li>Our understanding of the relationships among protist groups continues to change rapidly </li></ul><ul><li>One hypothesis divides all eukaryotes (including protists) into five supergroups </li></ul>
  13. 13. Fig. 28-03a Green algae Amoebozoans Opisthokonts Alveolates Stramenopiles Diplomonads Parabasalids Euglenozoans Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Excavata Chromalveolata Rhizaria Chlorarachniophytes Forams Radiolarians Archaeplastida Red algae Chlorophytes Charophyceans Land plants Unikonta Slime molds Gymnamoebas Entamoebas Nucleariids Fungi Choanoflagellates Animals
  14. 14. Fig. 28-03b Diplomonads Parabasalids Euglenozoans Excavata
  15. 15. Fig. 28-03c Alveolates Stramenopiles Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Chromalveolata
  16. 16. Fig. 28-03d Chlorarachniophytes Forams Radiolarians Rhizaria
  17. 17. Fig. 28-03e Red algae Chlorophytes Charophyceans Land plants Green algae Archaeplastida
  18. 18. Fig. 28-03f Choanoflagellates Animals Fungi Gymnamoebas Entamoebas Nucleariids Unikonta Slime molds Amoebozoans Opisthokonts
  19. 19. Fig. 28-03g 5 µm
  20. 20. Fig. 28-03h 50 µm
  21. 21. Fig. 28-03i 20 µm
  22. 22. Fig. 28-03j 20 µm 50 µm
  23. 23. Fig. 28-03l 100 µm
  24. 24. <ul><li>The clade Excavata is characterized by its cytoskeleton </li></ul><ul><li>Some members have a feeding groove </li></ul><ul><li>This controversial group includes the diplomonads, parabasalids, and euglenozoans </li></ul>Concept 28.2: Excavates include protists with modified mitochondria and protists with unique flagella
  25. 25. Fig. 28-UN1 Kinetoplastids Euglenids Diplomonads Parabasalids Euglenozoans Excavata Chromalveolata Rhizaria Archaeplastida Unikonta
  26. 26. Diplomonads and Parabasalids <ul><li>These 2 groups live in anaerobic environments, lack plastids, and have modified mitochondria </li></ul><ul><li>Diplomonads </li></ul><ul><ul><li>Have modified mitochondria called mitosomes </li></ul></ul><ul><ul><li>Derive energy anaerobically, for example, by glycolysis </li></ul></ul><ul><ul><li>Have two equal-sized nuclei and multiple flagella </li></ul></ul><ul><ul><li>Are often parasites, for example, Giardia intestinalis </li></ul></ul>
  27. 27. <ul><li>Parabasalids </li></ul><ul><ul><li>Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically </li></ul></ul><ul><ul><li>Include Trichomonas vaginalis , the pathogen that causes yeast infections in human females </li></ul></ul>
  28. 28. Fig. 28-04 5 µm Flagella Undulating membrane
  29. 29. Euglenozoans <ul><li>Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites </li></ul><ul><li>The main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella </li></ul><ul><li>This clade includes the kinetoplastids and euglenids </li></ul>
  30. 30. Fig. 28-05 Flagella Crystalline rod Ring of microtubules 0.2 µm
  31. 31. Kinetoplastids <ul><li>Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast </li></ul><ul><li>They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems </li></ul><ul><li>This group includes Trypanosoma , which causes sleeping sickness in humans </li></ul><ul><li>Another pathogenic trypanosome causes Chagas’ disease </li></ul>
  32. 32. Fig. 28-06 9 µm
  33. 33. Euglenids <ul><li>Euglenids have one or two flagella that emerge from a pocket at one end of the cell </li></ul><ul><li>Some species can be both autotrophic and heterotrophic </li></ul>Video: Euglena Video: Euglena Motion
  34. 34. Fig. 28-07 Long flagellum Eyespot Short flagellum Contractile vacuole Nucleus Chloroplast Plasma membrane Light detector Pellicle Euglena (LM) 5 µm
  35. 35. Concept 28.3: Chromalveolates may have originated by secondary endosymbiosis <ul><li>Some data suggest that the clade Chromalveolata is monophyletic and originated by a secondary endosymbiosis event </li></ul><ul><li>The proposed endosymbiont is a red alga </li></ul><ul><li>This clade is controversial and includes the alveolates and the stramenopiles </li></ul>
  36. 36. Fig. 28-UN2 Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Rhizaria Archaeplastida Unikonta Chromalveolata Excavata Alveolates Stramenopiles
  37. 37. Alveolates <ul><li>Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane </li></ul><ul><li>The function of the alveoli is unknown </li></ul><ul><li>Alveolata includes the dinoflagellates, apicomplexans, and ciliates </li></ul>
  38. 38. Fig. 28-08 Flagellum Alveoli Alveolate 0.2 µm
  39. 39. Dinoflagellates <ul><li>Dinoflagellates are a diverse group of aquatic mixotrophs and heterotrophs </li></ul><ul><li>They are abundant components of both marine and freshwater phytoplankton </li></ul><ul><li>Each has a characteristic shape that in many species is reinforced by internal plates of cellulose </li></ul>Video: Dinoflagellate
  40. 40. <ul><li>Two flagella make them spin as they move through the water </li></ul><ul><li>Dinoflagellate blooms are the cause of toxic “red tides” </li></ul>
  41. 41. Fig. 28-09 Flagella 3 µm
  42. 42. Apicomplexans <ul><li>Apicomplexans are parasites of animals, and some cause serious human diseases </li></ul><ul><li>One end, the apex , contains a complex of organelles specialized for penetrating a host </li></ul><ul><li>They have a nonphotosynthetic plastid, the apicoplast </li></ul><ul><li>Most have sexual and asexual stages that require two or more different host species for completion </li></ul>
  43. 43. <ul><li>The apicomplexan Plasmodium is the parasite that causes malaria </li></ul><ul><li>Plasmodium requires both mosquitoes and humans to complete its life cycle </li></ul><ul><li>Approximately 2 million people die each year from malaria </li></ul><ul><li>Efforts are ongoing to develop vaccines that target this pathogen </li></ul>
  44. 44. Fig. 28-10-1 0.5 µm Inside human Liver Liver cell Merozoite ( n ) Red blood cells Gametocytes ( n ) Haploid ( n ) Diploid (2 n ) Key Merozoite Apex Red blood cell
  45. 45. Fig. 28-10-2 0.5 µm Inside human Liver Liver cell Merozoite ( n ) Red blood cells Gametocytes ( n ) Haploid ( n ) Diploid (2 n ) Key Merozoite Apex Red blood cell Zygote (2 n ) FERTILIZATION Gametes Inside mosquito
  46. 46. Fig. 28-10-3 0.5 µm Inside human Liver Liver cell Merozoite ( n ) Red blood cells Gametocytes ( n ) Haploid ( n ) Diploid (2 n ) Key Merozoite Apex Red blood cell Zygote (2 n ) FERTILIZATION Gametes Inside mosquito MEIOSIS Oocyst Sporozoites ( n )
  47. 47. Ciliates <ul><li>Ciliates , a large varied group of protists, are named for their use of cilia to move and feed </li></ul><ul><li>They have large macronuclei and small micronuclei </li></ul><ul><li>The micronuclei function during conjugation, a sexual process that produces genetic variation </li></ul><ul><li>Conjugation is separate from reproduction, which generally occurs by binary fission </li></ul>
  48. 48. Fig. 28-11 Contractile vacuole Oral groove Cell mouth Cilia Micronucleus Macronucleus Food vacuoles (a) Feeding, waste removal, and water balance 50 µm MEIOSIS Compatible mates Diploid micronucleus Haploid micronucleus The original macronucleus disintegrates. Diploid micronucleus MICRONUCLEAR FUSION (b) Conjugation and reproduction Key ConjugationReproduction
  49. 49. Fig. 28-11a Contractile vacuole Cilia Micronucleus Macronucleus Oral groove Cell mouth Food vacuoles (a) Feeding, waste removal, and water balance 50 µm
  50. 50. Fig. 28-11b-1 Compatible mates Diploid micronucleus MEIOSIS Haploid micronucleus Key Conjugation Reproduction (b) Conjugation and reproduction
  51. 51. Fig. 28-11b-2 Compatible mates Diploid micronucleus MEIOSIS Haploid micronucleus Key Conjugation Reproduction (b) Conjugation and reproduction Diploid micronucleus MICRONUCLEAR FUSION The original macronucleus disintegrates.
  52. 52. Video: Vorticella Habitat Video: Vorticella Detail Video: Vorticella Cilia Video: Paramecium Vacuole Video: Paramecium Cilia
  53. 53. Stramenopiles <ul><li>The clade Stramenopila includes several groups of heterotrophs as well as certain groups of algae </li></ul><ul><li>Most have a “hairy” flagellum paired with a “smooth” flagellum </li></ul>
  54. 54. Fig. 28-12 Smooth flagellum Hairy flagellum 5 µm
  55. 55. Diatoms <ul><li>Diatoms are unicellular algae with a unique two-part, glass-like wall of hydrated silica </li></ul><ul><li>Diatoms usually reproduce asexually, and occasionally sexually </li></ul>
  56. 56. Fig. 28-13 3 µm
  57. 57. <ul><li>Diatoms are a major component of phytoplankton and are highly diverse </li></ul><ul><li>Fossilized diatom walls compose much of the sediments known as diatomaceous earth </li></ul>Video: Various Diatoms Video: Diatoms Moving
  58. 58. Golden Algae <ul><li>Golden algae are named for their color, which results from their yellow and brown carotenoids </li></ul><ul><li>The cells of golden algae are typically biflagellated, with both flagella near one end </li></ul><ul><li>All golden algae are photosynthetic, and some are also heterotrophic </li></ul><ul><li>Most are unicellular, but some are colonial </li></ul>
  59. 59. Fig. 28-14 25 µm Outer container Flagellum Living cell
  60. 60. Brown Algae <ul><li>Brown algae are the largest and most complex algae </li></ul><ul><li>All are multicellular, and most are marine </li></ul><ul><li>Brown algae include many species commonly called “seaweeds” </li></ul><ul><li>Brown algae have the most complex multicellular anatomy of all algae </li></ul>
  61. 61. <ul><li>Giant seaweeds called kelps live in deep parts of the ocean </li></ul><ul><li>The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus </li></ul><ul><li>The rootlike holdfast anchors the stemlike stipe , which in turn supports the leaflike blades </li></ul>
  62. 62. Fig. 28-15 Blade Stipe Holdfast
  63. 63. Alternation of Generations <ul><li>A variety of life cycles have evolved among the multicellular algae </li></ul><ul><li>The most complex life cycles include an alternation of generations , the alternation of multicellular haploid and diploid forms </li></ul><ul><li>Heteromorphic generations are structurally different, while isomorphic generations look similar </li></ul>
  64. 64. Fig. 28-16-1 10 cm Haploid ( n ) Diploid (2 n ) Key Sporangia Sporophyte (2 n ) Zoospore MEIOSIS Female Gametophytes ( n ) Egg Male Sperm
  65. 65. Fig. 28-16-2 10 cm Haploid ( n ) Diploid (2 n ) Key Sporangia Sporophyte (2 n ) Zoospore MEIOSIS Female Gametophytes ( n ) Egg Male Sperm FERTILIZATION Zygote (2 n ) Developing sporophyte Mature female gemetophyte ( n )
  66. 66. Oomycetes (Water Molds and Their Relatives) <ul><li>Oomycetes include water molds, white rusts, and downy mildews </li></ul><ul><li>They were once considered fungi based on morphological studies </li></ul><ul><li>Most oomycetes are decomposers or parasites </li></ul><ul><li>They have filaments (hyphae) that facilitate nutrient uptake </li></ul><ul><li>Their ecological impact can be great, as in Phytophthora infestans causing potato blight </li></ul>
  67. 67. Fig. 28-17-1 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2 n ) Zoosporangium (2 n ) Haploid ( n ) Diploid (2 n ) Key
  68. 68. Fig. 28-17-2 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2 n ) Zoosporangium (2 n ) Haploid ( n ) Diploid (2 n ) Key Oogonium Egg nucleus ( n ) Antheridial hypha with sperm nuclei ( n ) MEIOSIS
  69. 69. Fig. 28-17-3 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2 n ) Zoosporangium (2 n ) Haploid ( n ) Diploid (2 n ) Key Oogonium Egg nucleus ( n ) Antheridial hypha with sperm nuclei ( n ) MEIOSIS Zygote germination SEXUAL REPRODUCTION Zygotes (oospores) (2 n ) FERTILIZATION
  70. 70. Video: Water Mold Oogonium Video: Water Mold Zoospores
  71. 71. Concept 28.4: Rhizarians are a diverse group of protists defined by DNA similarities <ul><li>DNA evidence supports Rhizaria as a monophyletic clade </li></ul><ul><li>Amoebas move and feed by pseudopodia ; some but not all belong to the clade Rhizaria </li></ul><ul><li>Rhizarians include forams and radiolarians </li></ul>
  72. 72. Fig. 28-UN3 Chlorarachniophytes Foraminiferans Radiolarians Excavata Chromalveolata Archaeplastida Unikonta Rhizaria
  73. 73. Forams <ul><li>Foraminiferans , or forams , are named for porous, generally multichambered shells, called tests </li></ul><ul><li>Pseudopodia extend through the pores in the test </li></ul><ul><li>Foram tests in marine sediments form an extensive fossil record </li></ul>
  74. 74. Radiolarians <ul><li>Marine protists called radiolarians have tests fused into one delicate piece, usually made of silica </li></ul><ul><li>Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis </li></ul><ul><li>The pseudopodia of radiolarians radiate from the central body </li></ul>
  75. 75. Fig. 28-18 Pseudopodia 200 µm
  76. 76. Concept 28.5: Red algae and green algae are the closest relatives of land plants <ul><li>Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont </li></ul><ul><li>The photosynthetic descendants of this ancient protist evolved into red algae and green algae </li></ul><ul><li>Land plants are descended from the green algae </li></ul><ul><li>Archaeplastida is a supergroup used by some scientists and includes red algae, green algae, and land plants </li></ul>
  77. 77. Fig. 28-UN4 Chlorophytes Charophyceans Red algae Green algae Land plants Excavata Chromalveolata Rhizaria Archaeplastida Unikonta
  78. 78. Red Algae <ul><li>Red algae are reddish in color due to an accessory pigment call phycoerythrin, which masks the green of chlorophyll </li></ul><ul><li>The color varies from greenish-red in shallow water to dark red or almost black in deep water </li></ul><ul><li>Red algae are usually multicellular; the largest are seaweeds </li></ul><ul><li>Red algae are the most abundant large algae in coastal waters of the tropics </li></ul>
  79. 79. Fig. 28-19 Bonnemaisonia hamifera 20 cm 8 mm Dulse ( Palmaria palmata ) Nori. The red alga Porphyra is the source of a traditional Japanese food. The seaweed is grown on nets in shallow coastal waters. The harvested seaweed is spread on bamboo screens to dry. Paper-thin, glossy sheets of nori make a mineral-rich wrap for rice, seafood, and vegetables in sushi.
  80. 80. Fig. 28-19a Bonnemaisonia hamifera 8 mm
  81. 81. Fig. 28-19b Dulse ( Palmaria palmata ) 20 cm
  82. 82. Fig. 28-19c Nori. The red alga Porphyra is the source of a traditional Japanese food. The seaweed is grown on nets in shallow coastal waters. The harvested seaweed is spread on bamboo screens to dry. Paper-thin, glossy sheets of nori make a mineral-rich wrap for rice, seafood, and vegetables in sushi.
  83. 83. Green Algae <ul><li>Green algae are named for their grass-green chloroplasts </li></ul><ul><li>Plants are descended from the green algae </li></ul><ul><li>The two main groups are chlorophytes and charophyceans </li></ul>
  84. 84. <ul><li>Most chlorophytes live in fresh water, although many are marine </li></ul><ul><li>Other chlorophytes live in damp soil, as symbionts in lichens, or in snow </li></ul>
  85. 85. Fig. 28-20
  86. 86. <ul><li>Chlorophytes include unicellular, colonial, and multicellular forms </li></ul>Video: Volvox Female Spheroid Video: Volvox Daughter Video: Volvox Colony Video: Volvox Flagella Video: Volvox Inversion 1 Video: Volvox Inversion 2 Video: Volvox Sperm and Female
  87. 87. Fig. 28-21 (a) Ulva, or sea lettuce (b) Caulerpa , an intertidal chloro- phyte 2 cm
  88. 88. Fig. 28-21a (a) Ulva, or sea lettuce 2 cm
  89. 89. Fig. 28-21b (b) Caulerpa, an intertidal chloro- phyte
  90. 90. <ul><li>Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages </li></ul>Video: Chlamydomonas
  91. 91. Fig. 28-22-1 1 µm Flagella Cell wall Nucleus Cross section of cup-shaped chloroplast Mature cell ( n ) Zoospore ASEXUAL REPRODUCTION Haploid ( n ) Diploid (2 n ) Key
  92. 92. Fig. 28-22-2 1 µm Flagella Cell wall Nucleus Cross section of cup-shaped chloroplast Mature cell ( n ) Zoospore ASEXUAL REPRODUCTION Haploid ( n ) Diploid (2 n ) Key Gamete ( n ) Zygote (2 n ) SEXUAL REPRODUCTION MEIOSIS FERTILIZATION + + – –
  93. 93. Concept 28.6: Unikonts include protists that are closely related to fungi and animals <ul><li>The supergroup Unikonta includes animals, fungi, and some protists </li></ul><ul><li>This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists) </li></ul><ul><li>The root of the eukaryotic tree remains controversial </li></ul><ul><li>It is unclear whether unikonts separated from other eukaryotes relatively early or late </li></ul>
  94. 94. Fig. 28-UN5 Amoebozoans Nucleariids Fungi Choanoflagellates Animals Unikonta Excavata Chromalveolata Rhizaria Archaeplastida
  95. 95. Fig. 28-23 Common ancestor of all eukaryotes DHFR-TS gene fusion Unikonta Excavata Chromalveolata Rhizaria Archaeplastida Choanoflagellates Animals Fungi Amoebozoans Diplomonads Euglenozoans Alveolates Stramenopiles Rhizarians Red algae Green algae Plants RESULTS
  96. 96. Amoebozoans <ul><li>Amoebozoans are amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia </li></ul><ul><li>They include gymnamoebas, entamoebas, and slime molds </li></ul>
  97. 97. Slime Molds <ul><li>Slime molds, or mycetozoans, were once thought to be fungi </li></ul><ul><li>Molecular systematics places slime molds in the clade Amoebozoa </li></ul>
  98. 98. Plasmodial Slime Molds <ul><li>Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange </li></ul>Video: Plasmodial Slime Mold Streaming Video: Plasmodial Slime Mold
  99. 99. Fig. 28-24-1 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid ( n ) Diploid (2 n )
  100. 100. Fig. 28-24-2 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid ( n ) Diploid (2 n ) MEIOSIS Spores ( n ) Germinating spore Amoeboid cells ( n ) Flagellated cells ( n )
  101. 101. Fig. 28-24-3 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid ( n ) Diploid (2 n ) MEIOSIS Spores ( n ) Germinating spore Amoeboid cells ( n ) Flagellated cells ( n ) Zygote (2 n ) FERTILIZATION
  102. 102. <ul><li>At one point in the life cycle, plasmodial slime molds form a mass called a plasmodium (not to be confused with malarial Plasmodium ) </li></ul><ul><li>The plasmodium is undivided by membranes and contains many diploid nuclei </li></ul><ul><li>It extends pseudopodia through decomposing material, engulfing food by phagocytosis </li></ul>
  103. 103. Cellular Slime Molds <ul><li>Cellular slime molds form multicellular aggregates in which cells are separated by their membranes </li></ul><ul><li>Cells feed individually, but can aggregate to form a fruiting body </li></ul><ul><li>Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity </li></ul>
  104. 104. Fig. 28-25-1 Spores ( n ) Emerging amoeba ( n ) Solitary amoebas (feeding stage) ( n ) Aggregated amoebas Migrating aggregate Fruiting bodies ( n ) ASEXUAL REPRODUCTION 600 µm 200 µm Key Haploid ( n ) Diploid (2 n )
  105. 105. Fig. 28-25-2 Spores ( n ) Emerging amoeba ( n ) Solitary amoebas (feeding stage) ( n ) Aggregated amoebas Migrating aggregate Fruiting bodies ( n ) ASEXUAL REPRODUCTION 600 µm 200 µm Key Haploid ( n ) Diploid (2 n ) Amoebas ( n ) Zygote (2 n ) SEXUAL REPRODUCTION MEIOSIS FERTILIZATION
  106. 106. Gymnamoebas <ul><li>Gymnamoebas are common unicellular amoebozoans in soil as well as freshwater and marine environments </li></ul><ul><li>Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists </li></ul>Video: Amoeba Pseudopodia Video: Amoeba
  107. 107. Entamoebas <ul><li>Entamoebas are parasites of vertebrates and some invertebrates </li></ul><ul><li>Entamoeba histolytica causes amebic dysentery in humans </li></ul>
  108. 108. Opisthokonts <ul><li>Opisthokonts include animals, fungi, and several groups of protists </li></ul>
  109. 109. Concept 28.7: Protists play key roles in ecological relationships <ul><li>Protists are found in diverse aquatic environments </li></ul><ul><li>Protists often play the role of symbiont or producer </li></ul>
  110. 110. Symbiotic Protists <ul><li>Some protist symbionts benefit their hosts </li></ul><ul><ul><li>Dinoflagellates nourish coral polyps that build reefs </li></ul></ul><ul><ul><li>Hypermastigotes digest cellulose in the gut of termites </li></ul></ul>
  111. 111. Fig. 28-26 10 µm
  112. 112. <ul><li>Some protists are parasitic </li></ul><ul><ul><li>Plasmodium causes malaria </li></ul></ul><ul><ul><li>Pfesteria shumwayae is a dinoflagellate that causes fish kills </li></ul></ul><ul><ul><li>Phytophthora ramorum causes sudden oak death </li></ul></ul>
  113. 113. Fig. 28-27 Key Moderate risk High risk Low risk Nurseries with P. ramorum infections (2004) on other host plants (such as rhododendron).
  114. 114. Photosynthetic Protists <ul><li>Many protists are important producers that obtain energy from the sun </li></ul><ul><li>In aquatic environments, photosynthetic protists and prokaryotes are the main producers </li></ul><ul><li>The availability of nutrients can affect the concentration of protists </li></ul>
  115. 115. Fig. 28-28 Other consumers Herbivorous plankton Carnivorous plankton Bacteria absorbed by Soluble organic matter secrete Protistan producers
  116. 116. Fig. 28-UN6
  117. 117. Fig. 28-UN6a
  118. 118. Fig. 28-UN6b
  119. 119. Fig. 28-UN6c
  120. 120. Fig. 28-UN6d
  121. 121. Fig. 28-UN6e
  122. 122. Fig. 28-UN7
  123. 123. Fig. 28-UN8
  124. 124. You should now be able to: <ul><li>Explain why the kingdom Protista is no longer considered a legitimate taxon </li></ul><ul><li>Explain the process of endosymbiosis and state what living organisms are likely relatives of mitochondria and plastids </li></ul><ul><li>Distinguish between endosymbiosis and secondary endosymbiosis </li></ul><ul><li>Name the five supergroups, list their key characteristics, and describe some representative taxa </li></ul>

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