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Chapter 28: Protists What are protists?
(mostly) unicellular eukaryotes Autotrophic, heterotrophic or mixotrophic 3 nutritionally diverse groups Animal-like – ingestive – protozoa Plant-like – photosynthetic – algae Fungus-like – absorptive – water molds & slime molds Most motile with flagella or cilia aquatic How did eukaryotes originate? - Endosymbiosis
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Figure Endosymbiosis Serial endosymbiosis gave rise to proposed phylogenetic tree
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Figure 28.3 Diversity of plastids produced by secondary endosymbiosis
Cyanobacterium Heterotrophic eukaryote Primary endosymbiosis Red algae Green algae Secondary Plastid Dinoflagellates Apicomplexans Ciliates Stramenopiles Euglenids Chlorarachniophytes Alveolates Plastid – plant organelle
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Chapter 28: Protists What are protists? How did eukaryotes originate?
What is the evidence for endosymbiosis? Similarities between bacteria and mitochondria & chloroplasts Size Reproduction by binary fission Small, circular genomes DNA sequence Enzymes & transport systems tRNA & ribosomes for transcription & translation Current endosymbiotic relationships A survey of protists……
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Figure 28.5 Diplomonads and parabasalids
(a) Giardia intestinalis, a diplomonad (colorized SEM) (b) Trichomonas vaginalis, a parabasalid (colorized SEM) Flagella Undulating membrane Diplomonads 2 flagella 2 nuclei no mitochondria Simple cytoskeleton Giardia – water contamination severe cramping & diarrhea
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Figure 28.8 Euglena, a euglenid commonly found in pond water
Long flagellum Short flagellum Nucleus Plasma membrane Paramylon granule Chloroplast Contractile vacuole Light detector: swelling near the base of the long flagellum; detects light that is not blocked by the eyespot; as a result, Euglena moves toward light of appropriate intensity, an important adaptation that enhances photosynthesis Eyespot: pigmented organelle that functions as a light shield, allowing light from only a certain direction to strike the light detector Pellicle: protein bands beneath the plasma membrane that provide strength and flexibility (Euglena lacks a cell wall) Euglena (LM) 5 µm
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Fig. 28.7 Trypanosoma, the kinetoplastid that causes sleeping sickness
- Transmitted by the tsetse fly 9 m
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Alveolata Photosynthetic flagellates Flagellum Alveoli 0.2 µm
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Photosynthetic flagellates Dinoflagellates most unicellular 2 flagella
Alveolata Photosynthetic flagellates Dinoflagellates most unicellular 2 flagella blooms – red tide form symbiotic relationships with Cnidarians (coral in reefs) 3 µm Flagella
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Plasmodium does not grow well in RBC of sickle-cell heterozygotes
Figure The two-host life cycle of Plasmodium, the apicomplexan that causes malaria Inside mosquito Inside human Sporozoites (n) Oocyst MEIOSIS Liver Liver cell Merozoite Red blood cells Gametocytes FERTILIZATION Gametes Zygote (2n) Key Haploid (n) Diploid (2n) cell Apex 0.5 µm An infected Anopheles mosquito bites a person, injecting Plasmodium sporozoites in its saliva. The sporozoites enter the person’s liver cells. After several days, the sporozoites undergo multiple divisions and become merozoites, which use their apical complex to penetrate red blood cells (see TEM below). The merozoites divide asexually inside the red blood cells. At intervals of 48 or 72 hours (depending on the species), large numbers of merozoites break out of the blood cells, causing periodic chills and fever. Some of the merozoites infect new red blood cells. Some merozoites form gametocytes. Gametes form from gametocytes. Fertilization occurs in the mosquito’s digestive tract, and a zygote forms. The zygote is the only diploid stage in the life cycle. Another Anopheles mosquito bites the infected person and picks up Plasmodium gametocytes along with blood. An oocyst develops from the zygote in the wall of the mosquito’s gut. The oocyst releases thousands of sporozoites, which migrate to the mosquito’s salivary gland. 1 2 3 4 5 6 7 Apicomplexans organelles at apex parasites Plasmodium does not grow well in RBC of sickle-cell heterozygotes
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Figure 28.12 Structure and Function in the Ciliate Paramecium caudatum
Thousands of cilia cover the surface of Paramecium. The undigested contents of food vacuoles are released when the vacuoles fuse with a specialized region of the plasma membrane that functions as an anal pore. Paramecium, like other freshwater protists, constantly takes in water by osmosis from the hypotonic environment. Bladderlike contractile vacuoles accumulate excess water from radial canals and periodically expel it through the plasma membrane. Food vacuoles combine with lysosomes. As the food is digested, the vacuoles follow a looping path through the cell. Paramecium feeds mainly on bacteria. Rows of cilia along a funnel-shaped oral groove move food into the cell mouth, where the food is engulfed into food vacuoles by phagocytosis. Oral groove Cell mouth Micronucleus Macronucleus FEEDING, WASTE REMOVAL, AND WATER BALANCE Contractile vacuole Ciliates Use cilia to move & feed solitary cells in fresh water 2 types of nuclei – large macronucleus & several micronuclei Paramecium & Stentor
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Stramenopila (straw hair)
Water molds & relatives heterotrophic decompose dead fish Diatoms yellow or brown glass-like cell walls of hydrated silica fresh water & marine toothpaste, car paint, diatomaceous earth (swimming pools) Synedra
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Figure 28.16 Diatom diversity (LM)
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Stramenopila (straw hair)
Water molds & relatives heterotrophic decompose dead fish Diatoms yellow or brown glass-like cell walls of hydrated silica toothpaste, car paint, diatomaceous earth (swimming pools) Synedra Golden algae (Chrysophyta) golden & brown carotene & xanthophyll accessory pigments 2 flagella at same end Brown algae (Phaeophyta) largest, most complex algae multicellular & most are marine along temperate coasts where water is cool sea weeds, kelp
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Figure A kelp forest
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Figure 28.20 Edible seaweed (a) The seaweed is grown on nets in
shallow coastal waters. (b) A worker spreads the harvested sea- weed on bamboo screens to dry. (c) Paper-thin, glossy sheets of nori make a mineral-rich wrap for rice, seafood, and vegetables in sushi.
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Protozoa with pseudopodia Gymnamoeba Entamoeba amoebic dysentery
Amoebazoa Protozoa with pseudopodia Gymnamoeba Entamoeba amoebic dysentery Plasmodial slime molds most brightly pigmented feeding stage is amoeboid plasmodium Pseudopodia 40 µm
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Protozoa with pseudopodia Gymnamoeba Entamoeba amoebic dysentery
Amoebazoa Protozoa with pseudopodia Gymnamoeba Entamoeba amoebic dysentery Plasmodial slime molds most brightly pigmented feeding stage is amoeboid plasmodium Cellular slime molds 4 cm
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Red algae (Rhodophyta) No flagellated stage phycoerythrin
multicellular along tropical marine coasts Bonnemaisonia hamifera. This red alga has a filamentous form. (a) Dulse (Palmaria palmata). This edible species has a “leafy” form. (b) A coralline alga. The cell walls of coralline algae are hardened by calcium carbonate. Some coralline algae are members of the biological communities around coral reefs. (c)
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Figure 28.4 A tentative phylogeny of eukaryotes
Diplomonads Parabasalids Kinetoplastids Euglenids Dinoflagellates Apicomplexans Ciliates Oomycetes Diatoms Golden algae Brown algae Chlorarachniophytes Foraminiferans Radiolarians Gymnamoebas Entamoebas Plasmodial slime molds Cellular slime molds Fungi Choanoflagellates Metazoans Red algae Chlorophytes Charophyceans Plants Ancestral eukaryote Chlorophyta Plantae Rhodophyta Animalia (Opisthokonta) (Viridiplantae) Diplomonadida Parabasala Euglenozoa Alveolata Stramenopila Cercozoa Radiolaria Amoebozoa
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Green algae (Chlorophyta)
Closely related to plants most fresh water (some marine) lichens – mutualistic relationship between green algae & fungi
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Figure 28.30 Colonial and multicellular chlorophytes
Volvox, a colonial freshwater chlorophyte. The colony is a hollow ball whose wall is composed of hundreds or thousands of biflagellated cells (see inset LM) embedded in a gelatinous matrix. The cells are usually connected by strands of cytoplasm; if isolated, these cells cannot reproduce. The large colonies seen here will eventually release the small “daughter” colonies within them (LM). (a) Caulerpa, an inter- tidal chlorophyte. The branched fila- ments lack cross-walls and thus are multi- nucleate. In effect, the thallus is one huge “supercell.” (b) Ulva, or sea lettuce. This edible seaweed has a multicellular thallus differentiated into leaflike blades and a rootlike holdfast that anchors the alga against turbulent waves and tides. (c) 20 µm 50 µm
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