1. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 28 Protists

2. Explain the process of endosymbiosis and state what living organisms are likely relatives of mitochondria and plastids Endosymbiosis is the process in which certain unicellular organisms engulf other cells which becomes endosymbionts and ultimately organelles in the host cell. For example: 1.The first eukaryotes acquired mitochondria by engulfing an aerobic prokaryote (alpha proteobacterium) that evolved into mitochondria 2.Later heterotrophic eukaryotes acquired an additional endosymbiont (photosynthetic cyanobacterium) that evolved into plastids

3. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Living Small Even a low-power microscope can reveal a great variety of organisms in a drop of pond water Protist is the informal name of the kingdom of mostly unicellular eukaryotes Advances in eukaryotic systematics have caused the classification of protists to change significantly Protists constitute a paraphyletic group, and Protista is no longer valid as a kingdom

4. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings FungusPlantsAnimals Multicellular (mostly) Multicellular HeterotrophicAutotrophic (Photosynthetic) Heterotrophic Cell walls (chitin)Cell Wall (cellulose) No cell wall (plasma membrane)

5. Fig. 28-01 1 µm

6. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.1: Most eukaryotes are single-celled organisms Protists are eukaryotes and thus have organelles and are more complex than prokaryotes Most protists are unicellular, but there are some colonial and multicellular species

7. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Structural and Functional Diversity in Protists Protists exhibit more structural and functional diversity than any other group of eukaryotes Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell

8. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protists, the most nutritionally diverse of all eukaryotes, include: – Photoautotrophs, which contain chloroplasts – Heterotrophs, which absorb organic molecules or ingest larger food particles – Mixotrophs, which combine photosynthesis and heterotrophic nutrition Protists can reproduce asexually or sexually, or by the sexual processes of meiosis and syngamy (conjugation and an alternation of generations)

9. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much protist diversity has its origins in endosymbiosis Mitochondria evolved by endosymbiosis of an aerobic prokaryote Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium

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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The plastid-bearing lineage of protists evolved into red algae and green algae On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis, in which they were ingested by a heterotrophic eukaryote

12. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Five Supergroups of Eukaryotes It is no longer thought that amitochondriates (lacking mitochondria) are the oldest lineage of eukaryotes Our understanding of the relationships among protist groups continues to change rapidly One hypothesis divides all eukaryotes (including protists) into five supergroups

13. Fig. 28-03a Green algae Amoebozoans Opisthokonts Alveolate s Stramenopiles Diplomonads Parabasalids Euglenozoans Dinoflagellates Apicomplexan s 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. Fig. 28-UN6

15. Giardia intestinalis

16. Diatom diversity

17. Globigerina

18. Volvox (green alga)

19. Amoeba

20. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The clade Excavata is characterized by its cytoskeleton Some members have a feeding groove This controversial group includes the diplomonads, parabasalids, and euglenozoans Concept 28.2: Excavates include protists with modified mitochondria and protists with unique flagella

21. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 28-UN1 Kinetoplastids Euglenids Diplomonads Parabasalids Euglenozoans Excavata Chromalveolata Rhizaria Archaeplastida Unikonta

22. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Diplomonads and Parabasalids These 2 groups live in anaerobic environments, lack plastids, and have modified mitochondria Diplomonads – Have modified mitochondria called mitosomes – Derive energy anaerobically, for example, by glycolysis – Have two equal-sized nuclei and multiple flagella – Are often parasites, for example, Giardia intestinalis

23. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Parabasalids – Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically – Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females

24. Fig. 28-04 5 µm Flagella Undulating membrane

25. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Euglenozoans Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites The main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella This clade includes the kinetoplastids and euglenids

26. Fig. 28-05 Flagella Crystalline rod Ring of microtubules 0.2 µm

27. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Kinetoplastids Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems This group includes Trypanosoma, which causes sleeping sickness in humans Another pathogenic trypanosome causes Chagas’ disease

28. Fig. 28-06 9 µm

29. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Euglenids Euglenids have one or two flagella that emerge from a pocket at one end of the cell Some species can be both autotrophic and heterotrophic Video: Euglena Video: Euglena Video: Euglena Motion Video: Euglena Motion

30. Fig. 28-07 Long flagellum Eyespot Short flagellum Contractile vacuole Nucleus Chloroplast Plasma membrane Light detector Pellicle Euglena (LM) 5 µm

31. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.3: Chromalveolates may have originated by secondary endosymbiosis Some data suggest that the clade Chromalveolata is monophyletic and originated by a secondary endosymbiosis event The proposed endosymbiont is a red alga This clade is controversial and includes the alveolates and the stramenopiles

32. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 28-UN2 Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Rhizaria Archaeplastida Unikonta Chromalveolata Excavata Alveolates Stramenopiles

33. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Alveolates Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane The function of the alveoli is unknown Alveolata includes the dinoflagellates, apicomplexans, and ciliates

34. Fig. 28-08 Flagellum Alveoli Alveolate 0.2 µm

35. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Dinoflagellates Dinoflagellates are a diverse group of aquatic mixotrophs and heterotrophs They are abundant components of both marine and freshwater phytoplankton Each has a characteristic shape that in many species is reinforced by internal plates of cellulose Video: Dinoflagellate Video: Dinoflagellate

36. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Two flagella make them spin as they move through the water Dinoflagellate blooms are the cause of toxic “red tides”

37. Fig. 28-09 Flagella 3 µm

38. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Apicomplexans Apicomplexans are parasites of animals, and some cause serious human diseases One end, the apex, contains a complex of organelles specialized for penetrating a host They have a nonphotosynthetic plastid, the apicoplast Most have sexual and asexual stages that require two or more different host species for completion

39. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The apicomplexan Plasmodium is the parasite that causes malaria Plasmodium requires both mosquitoes and humans to complete its life cycle Approximately 2 million people die each year from malaria Efforts are ongoing to develop vaccines that target this pathogen

40. Fig. 28-10-1 0.5 µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell

41. Fig. 28-10-2 0.5 µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito

42. Fig. 28-10-3 0.5 µm Inside human Liver Liver cell Merozoite (n) Red blood cells Gametocytes (n) Haploid (n) Diploid (2n) Key Merozoite Apex Red blood cell Zygote (2n) FERTILIZATION Gametes Inside mosquito MEIOSIS Oocyst Sporozoites (n)

43. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ciliates Ciliates, a large varied group of protists, are named for their use of cilia to move and feed They have large macronuclei and small micronuclei The micronuclei function during conjugation, a sexual process that produces genetic variation Conjugation is separate from reproduction, which generally occurs by binary fission

44. 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 Conjugation Reproduction

45. Fig. 28-11a Contractile vacuole Cilia Micronucleus Macronucleus Oral groove Cell mouth Food vacuoles (a) Feeding, waste removal, and water balance 50 µm

46. Fig. 28-11b-1 Compatible mates Diploid micronucleus MEIOSIS Haploid micronucleus Key Conjugation Reproduction (b) Conjugation and reproduction

47. 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.

48. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Video: Vorticella Habitat Video: Vorticella Habitat Video: Vorticella Detail Video: Vorticella Detail Video: Vorticella Cilia Video: Vorticella Cilia Video: Paramecium Vacuole Video: Paramecium Vacuole Video: Paramecium Cilia Video: Paramecium Cilia

49. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Stramenopiles The clade Stramenopila includes several groups of heterotrophs as well as certain groups of algae Most have a “hairy” flagellum paired with a “smooth” flagellum

50. Fig. 28-12 Smooth flagellum Hairy flagellum 5 µm

51. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Diatoms Diatoms are unicellular algae with a unique two-part, glass-like wall of hydrated silica Diatoms usually reproduce asexually, and occasionally sexually

52. Fig. 28-13 3 µm

53. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Diatoms are a major component of phytoplankton and are highly diverse Fossilized diatom walls compose much of the sediments known as diatomaceous earth Video: Various Diatoms Video: Various Diatoms Video: Diatoms Moving Video: Diatoms Moving

54. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Golden Algae Golden algae are named for their color, which results from their yellow and brown carotenoids The cells of golden algae are typically biflagellated, with both flagella near one end All golden algae are photosynthetic, and some are also heterotrophic Most are unicellular, but some are colonial

55. Fig. 28-14 25 µm Outer container Flagellum Living cell

56. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Brown Algae Brown algae are the largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called “seaweeds” Brown algae have the most complex multicellular anatomy of all algae

57. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades

58. Fig. 28-15 Blade Stipe Holdfast

59. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Alternation of Generations A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms Heteromorphic generations are structurally different, while isomorphic generations look similar

60. Fig. 28-16-1 10 cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm

61. Fig. 28-16-2 10 cm Haploid (n) Diploid (2n) Key Sporangia Sporophyte (2n) Zoospore MEIOSIS Female Gametophytes (n) Egg Male Sperm FERTILIZATION Zygote (2n) Developing sporophyte Mature female gemetophyte (n)

62. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Oomycetes (Water Molds and Their Relatives) Oomycetes include water molds, white rusts, and downy mildews They were once considered fungi based on morphological studies Most oomycetes are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in Phytophthora infestans causing potato blight

63. Fig. 28-17-1 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2n) Zoosporangium (2n) Haploid (n) Diploid (2n) Key

64. Fig. 28-17-2 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2n) Zoosporangium (2n) Haploid (n) Diploid (2n) Key Oogonium Egg nucleus (n) Antheridial hypha with sperm nuclei (n) MEIOSIS

65. Fig. 28-17-3 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore (2n) Zoosporangium (2n) Haploid (n) Diploid (2n) Key Oogonium Egg nucleus (n) Antheridial hypha with sperm nuclei (n) MEIOSIS Zygote germination SEXUAL REPRODUCTION Zygotes (oospores) (2n) FERTILIZATION

66. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Video: Water Mold Oogonium Video: Water Mold Oogonium Video: Water Mold Zoospores Video: Water Mold Zoospores

67. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.4: Rhizarians are a diverse group of protists defined by DNA similarities DNA evidence supports Rhizaria as a monophyletic clade Amoebas move and feed by pseudopodia; some but not all belong to the clade Rhizaria Rhizarians include forams and radiolarians

68. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 28-UN3 Chlorarachniophytes Foraminiferans Radiolarians Excavata Chromalveolata Archaeplastida Unikonta Rhizaria

69. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Forams Foraminiferans, or forams, are named for porous, generally multichambered shells, called tests Pseudopodia extend through the pores in the test Foram tests in marine sediments form an extensive fossil record

70. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Radiolarians Marine protists called radiolarians have tests fused into one delicate piece, usually made of silica Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis The pseudopodia of radiolarians radiate from the central body

71. Fig. 28-18 Pseudopodia 200 µm

72. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.5: Red algae and green algae are the closest relatives of land plants Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont The photosynthetic descendants of this ancient protist evolved into red algae and green algae Land plants are descended from the green algae Archaeplastida is a supergroup used by some scientists and includes red algae, green algae, and land plants

73. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 28-UN4 Chlorophytes Charophyceans Red algae Green algae Land plants Excavata Chromalveolata Rhizaria Archaeplastida Unikonta

74. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Red Algae Red algae are reddish in color due to an accessory pigment call phycoerythrin, which masks the green of chlorophyll The color varies from greenish-red in shallow water to dark red or almost black in deep water Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics

75. 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.

76. Fig. 28-19a Bonnemaisonia hamifera 8 mm

77. Fig. 28-19b Dulse (Palmaria palmata) 20 cm

78. 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.

79. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Green Algae Green algae are named for their grass-green chloroplasts Plants are descended from the green algae The two main groups are chlorophytes and charophyceans

80. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Most chlorophytes live in fresh water, although many are marine Other chlorophytes live in damp soil, as symbionts in lichens, or in snow

81. Fig. 28-20

82. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chlorophytes include unicellular, colonial, and multicellular forms Video: Volvox Female Spheroid Video: Volvox Female Spheroid Video: Volvox Daughter Video: Volvox Daughter Video: Volvox Colony Video: Volvox Colony Video: Volvox Flagella Video: Volvox Flagella Video: Volvox Inversion 1 Video: Volvox Inversion 1 Video: Volvox Inversion 2 Video: Volvox Inversion 2 Video: Volvox Sperm and Female Video: Volvox Sperm and Female

83. Fig. 28-21 (a) Ulva, or sea lettuce (b) Caulerpa, an intertidal chloro- phyte 2 cm

84. Fig. 28-21a (a) Ulva, or sea lettuce 2 cm

85. Fig. 28-21b (b) Caulerpa, an intertidal chloro- phyte

86. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages Video: Chlamydomonas Video: Chlamydomonas

87. 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 (2n) Key

88. 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 (2n) Key Gamete (n) Zygote (2n) SEXUAL REPRODUCTION MEIOSIS FERTILIZATION + + – –

89. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.6: Unikonts include protists that are closely related to fungi and animals The supergroup Unikonta includes animals, fungi, and some protists This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists) The root of the eukaryotic tree remains controversial It is unclear whether unikonts separated from other eukaryotes relatively early or late

90. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 28-UN5 Amoebozoans Nucleariids Fungi Choanoflagellates Animals Unikonta Excavata Chromalveolata Rhizaria Archaeplastida

91. 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

92. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amoebozoans Amoebozoans are amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia They include gymnamoebas, entamoebas, and slime molds

93. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Slime Molds Slime molds, or mycetozoans, were once thought to be fungi Molecular systematics places slime molds in the clade Amoebozoa

94. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Plasmodial Slime Molds Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange Video: Plasmodial Slime Mold Streaming Video: Plasmodial Slime Mold Streaming Video: Plasmodial Slime Mold Video: Plasmodial Slime Mold

95. Fig. 28-24-1 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid (n) Diploid (2n)

96. Fig. 28-24-2 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid (n) Diploid (2n) MEIOSIS Spores (n) Germinating spore Amoeboid cells (n) Flagellated cells (n)

97. Fig. 28-24-3 Feeding plasmodium Mature plasmodium (preparing to fruit) Young sporangium Mature sporangium Stalk 4 cm 1 mm Key Haploid (n) Diploid (2n) MEIOSIS Spores (n) Germinating spore Amoeboid cells (n) Flagellated cells (n) Zygote (2n) FERTILIZATION

98. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings At one point in the life cycle, plasmodial slime molds form a mass called a plasmodium (not to be confused with malarial Plasmodium) The plasmodium is undivided by membranes and contains many diploid nuclei It extends pseudopodia through decomposing material, engulfing food by phagocytosis

99. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cellular Slime Molds Cellular slime molds form multicellular aggregates in which cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity

100. 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 (2n)

101. 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 (2n) Amoebas (n) Zygote (2n) SEXUAL REPRODUCTION MEIOSIS FERTILIZATION

102. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gymnamoebas Gymnamoebas are common unicellular amoebozoans in soil as well as freshwater and marine environments Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists Video: Amoeba Pseudopodia Video: Amoeba Pseudopodia Video: Amoeba Video: Amoeba

103. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Entamoebas Entamoebas are parasites of vertebrates and some invertebrates Entamoeba histolytica causes amebic dysentery in humans

104. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Opisthokonts Opisthokonts include animals, fungi, and several groups of protists

105. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 28.7: Protists play key roles in ecological relationships Protists are found in diverse aquatic environments Protists often play the role of symbiont or producer

106. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Symbiotic Protists Some protist symbionts benefit their hosts – Dinoflagellates (Alveolates) nourish coral polyps that build reefs – Hypermastigotes (Parabasalids) digest cellulose in the gut of termites

107. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Some protists are parasitic – Plasmodium is a dinoflagellate that causes malaria – Pfesteria shumwayae is a dinoflagellate that causes fish kills – Phytophthora ramorum is a oomycete that causes sudden oak death

108. Fig. 28-27 Key Moderate risk High risk Low risk Nurseries with P. ramorum infections (2004) on other host plants (such as rhododendron).

109. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Photosynthetic Protists Many protists are important producers that obtain energy from the sun In aquatic environments, photosynthetic protists and prokaryotes are the main producers The availability of nutrients can affect the concentration of protists

110. Fig. 28-28 Other consumers Herbivorous plankton Carnivorous plankton Bacteria absorbed by Soluble organic matter secrete Protistan producers

111. Fig. 28-UN7

112. Fig. 28-UN8

113. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings You should now be able to: 1.Explain why the kingdom Protista is no longer considered a legitimate taxon 2.Explain the process of endosymbiosis and state what living organisms are likely relatives of mitochondria and plastids 3.Distinguish between endosymbiosis and secondary endosymbiosis 4.Name the five supergroups, list their key characteristics, and describe some representative taxa