Chapter 27: Protists and the Dawn of the Eukarya CHAPTER 27 Protists and the Dawn of the Eukarya

Chapter 27: Protists and the Dawn of the Eukarya Protists Defined Protists Defined The Origin of the Eukaryotic Cell The Origin of the Eukaryotic Cell General Biology of the Protists General Biology of the Protists Protist Diversity Protist Diversity

Chapter 27: Protists and the Dawn of the Eukarya Euglenozoa Alveolata Stramenopila Rhodophyta

Chapter 27: Protists and the Dawn of the Eukarya Chlorophyta Choanoflagellida A History of Endosymbiosis A History of Endosymbiosis Some Recurrent Body Forms Some Recurrent Body Forms

Chapter 27: Protists and the Dawn of the Eukarya Protists Defined In this book we define the protists as all eukaryotes that are not plants, fungi, or animals.In this book we define the protists as all eukaryotes that are not plants, fungi, or animals. They are not a monophyletic group.They are not a monophyletic group.5

Chapter 27: Protists and the Dawn of the Eukarya The Origin of the Eukaryotic Cell The modern eukaryotic cell arose from an ancestral prokaryote.The modern eukaryotic cell arose from an ancestral prokaryote. Probable steps included loss of the cell wall and inward folding of the plasma membrane.Probable steps included loss of the cell wall and inward folding of the plasma membrane. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya The Origin of the Eukaryotic Cell An infolded plasma membrane attached to the chromosome may have led to formation of a nuclear envelope.An infolded plasma membrane attached to the chromosome may have led to formation of a nuclear envelope. A primitive cytoskeleton evolved.A primitive cytoskeleton evolved. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya The Origin of the Eukaryotic Cell The first truly eukaryotic cell was larger than its prokaryote ancestor, and possibly possessed one or more eukaryotic type flagella.The first truly eukaryotic cell was larger than its prokaryote ancestor, and possibly possessed one or more eukaryotic type flagella.11

Chapter 27: Protists and the Dawn of the Eukarya The Origin of the Eukaryotic Cell Prokaryotic cells incorporated as endosymbionts gave rise to eukaryotic organelles.Prokaryotic cells incorporated as endosymbionts gave rise to eukaryotic organelles. Peroxisomes may have been the first organelles of endosymbiotic origin.Peroxisomes may have been the first organelles of endosymbiotic origin. Mitochondria evolved from proteobacteria,Mitochondria evolved from proteobacteria, Chloroplasts from cyanobacteria.Chloroplasts from cyanobacteria. Cells with nuclei probably appeared before those with mitochondria.Cells with nuclei probably appeared before those with mitochondria. Review Figure

Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists Most protists are aquatic; some live within other organisms.Most protists are aquatic; some live within other organisms. The great majority are unicellular and microscopic but, many are multicellular and a few are enormous.The great majority are unicellular and microscopic but, many are multicellular and a few are enormous.13

Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists “Protozoan” is an outdated term applied to protists once classified as animals.“Protozoan” is an outdated term applied to protists once classified as animals. “Alga” is an outdated term applied to photosynthetic protists.“Alga” is an outdated term applied to photosynthetic protists.14

Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists Protists vary in modes of nutrition, metabolism, and locomotion.Protists vary in modes of nutrition, metabolism, and locomotion. Some protist cells contain contractile vacuoles, some digest food in food vacuoles.Some protist cells contain contractile vacuoles, some digest food in food vacuoles. Review Figures 27.5,

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Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists Protists have a variety of cell surfaces, some of them protective.Protists have a variety of cell surfaces, some of them protective.18

Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists Many protists contain endosymbiotic prokaryotes.Many protists contain endosymbiotic prokaryotes. Some are endosymbiotic in other cells, including other protists.Some are endosymbiotic in other cells, including other protists. Some endosymbiotic protists perform photosynthesis.Some endosymbiotic protists perform photosynthesis.19

Chapter 27: Protists and the Dawn of the Eukarya General Biology of the Protists Most protists reproduce both asexually and sexually.Most protists reproduce both asexually and sexually.20

Chapter 27: Protists and the Dawn of the Eukarya Protist Diversity Molecular and other techniques are enabling biologists to identify many monophyletic groups of protists.Molecular and other techniques are enabling biologists to identify many monophyletic groups of protists. Review Figure 27.9, Table

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Chapter 27: Protists and the Dawn of the Eukarya Euglenozoa The Euglenozoa are a monophyletic group of unicellular protists with flagella.The Euglenozoa are a monophyletic group of unicellular protists with flagella.24

Chapter 27: Protists and the Dawn of the Eukarya Euglenozoa Euglenoids are Euglenozoa that are often photosynthetic and have anterior flagella.Euglenoids are Euglenozoa that are often photosynthetic and have anterior flagella. See figure 10

Chapter 27: Protists and the Dawn of the Eukarya Euglenozoa Kinetoplastids are Euglenozoa that have a single, large mitochondrion, in which RNA is edited.Kinetoplastids are Euglenozoa that have a single, large mitochondrion, in which RNA is edited.26

Chapter 27: Protists and the Dawn of the Eukarya Alveolata The Alveolata are a monophyletic group of unicellular organisms with alveoli beneath their plasma membranes.The Alveolata are a monophyletic group of unicellular organisms with alveoli beneath their plasma membranes.27

Chapter 27: Protists and the Dawn of the Eukarya Alveolata Dinoflagellates are marine alveolates with a unique color.Dinoflagellates are marine alveolates with a unique color. They are major contributors to world photosynthesis.They are major contributors to world photosynthesis. Many are endosymbionts; they contribute to coral reef growth.Many are endosymbionts; they contribute to coral reef growth. Dinoflagellates cause“red tides.”Dinoflagellates cause“red tides.”28

Chapter 27: Protists and the Dawn of the Eukarya Alveolata Apicomplexans are parasitic alveolates.Apicomplexans are parasitic alveolates. Their spores, containing a mass of organelles, are adapted to the invasion of host tissue.Their spores, containing a mass of organelles, are adapted to the invasion of host tissue. The apicomplexan Plasmodium causes malaria.The apicomplexan Plasmodium causes malaria. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya Alveolata Ciliates are alveolates that move via cilia and have two kinds of nuclei.Ciliates are alveolates that move via cilia and have two kinds of nuclei. The macronuclei control the cell with transcription and translation,and are responsible for genetic recombination by conjugation.The macronuclei control the cell with transcription and translation,and are responsible for genetic recombination by conjugation. Some ciliates have a complex internal structure.Some ciliates have a complex internal structure. Review Figures 27.15, 27.16,

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Chapter 27: Protists and the Dawn of the Eukarya Stramenopila Stramenopiles typically have two flagella of unequal length, the longer bearing rows of tubular hairs.Stramenopiles typically have two flagella of unequal length, the longer bearing rows of tubular hairs. Some groups are photosynthetic.Some groups are photosynthetic.36

Chapter 27: Protists and the Dawn of the Eukarya Stramenopila Diatoms are unicellular stramenopiles, many of which have complex, two-part, glassy cell walls.Diatoms are unicellular stramenopiles, many of which have complex, two-part, glassy cell walls. They contribute to world photosynthesis.They contribute to world photosynthesis. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya Stramenopila The brown algae are predominantly multicellular, photosynthetic stramenopiles.The brown algae are predominantly multicellular, photosynthetic stramenopiles. They include the largest of all protists.They include the largest of all protists. Some show considerable tissue differentiation.Some show considerable tissue differentiation.39

Chapter 27: Protists and the Dawn of the Eukarya Stramenopila In many multicellular photosynthetic protists and all plants, haploid and diploid cells undergo mitosis and alternation of generations.In many multicellular photosynthetic protists and all plants, haploid and diploid cells undergo mitosis and alternation of generations. The diploid sporophyte generation forms spores by meiosis which become haploid.The diploid sporophyte generation forms spores by meiosis which become haploid. The haploid gametophyte generation forms gametes by mitosis and yields zygotes: the next generation of sporophytes.The haploid gametophyte generation forms gametes by mitosis and yields zygotes: the next generation of sporophytes. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya Stramenopila Oomycetes are a group of nonphotosynthetic stramenopiles.Oomycetes are a group of nonphotosynthetic stramenopiles. The oomycetes are coenocytic.The oomycetes are coenocytic. They are diploid for most of their life cycle.They are diploid for most of their life cycle.42

Chapter 27: Protists and the Dawn of the Eukarya Rhodophyta Red algae (Rhodophyta) are multicellular, photosynthetic protists that have a characteristic storage product (floridean starch) and lack flagellated reproductive cells.Red algae (Rhodophyta) are multicellular, photosynthetic protists that have a characteristic storage product (floridean starch) and lack flagellated reproductive cells.43

Chapter 27: Protists and the Dawn of the Eukarya Chlorophyta The Chlorophyta are often multicellular, contain chlorophylls a and b, and use starch as a storage product.The Chlorophyta are often multicellular, contain chlorophylls a and b, and use starch as a storage product. Their life cycles include the isomorphic alternation of generations of Ulva and the haplontic life cycle of Ulothrix.Their life cycles include the isomorphic alternation of generations of Ulva and the haplontic life cycle of Ulothrix. Review Figures 27.26,

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Chapter 27: Protists and the Dawn of the Eukarya Chlorophyta The chlorophytes are sister to a lineage including other green algae and the plant kingdom.The chlorophytes are sister to a lineage including other green algae and the plant kingdom.47

Chapter 27: Protists and the Dawn of the Eukarya Choanoflagellida The Choanoflagellida are protists with flagella and a body type similar to a characteristic type of sponge cell.The Choanoflagellida are protists with flagella and a body type similar to a characteristic type of sponge cell. The Choanoflagellida are sister to the animal kingdom.The Choanoflagellida are sister to the animal kingdom.48

Chapter 27: Protists and the Dawn of the Eukarya A History of Endosymbiosis Primary endosymbiosis of a cyanobacterium and a eukaryote gave rise to the chloroplasts of green algae, plants, and red algae.Primary endosymbiosis of a cyanobacterium and a eukaryote gave rise to the chloroplasts of green algae, plants, and red algae. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya A History of Endosymbiosis Secondary endosymbiosis of eukaryotes with unicellular green or red algae gave rise to the chloroplasts of euglenoids, stramenopiles, and other groups.Secondary endosymbiosis of eukaryotes with unicellular green or red algae gave rise to the chloroplasts of euglenoids, stramenopiles, and other groups. A cell of one of those groups, in tertiary endosymbiosis, gave rise to another type of chloroplast.A cell of one of those groups, in tertiary endosymbiosis, gave rise to another type of chloroplast.51

Chapter 27: Protists and the Dawn of the Eukarya Some Recurrent Body Forms Some similar body forms are found in several different, unrelated protist groups.Some similar body forms are found in several different, unrelated protist groups. Review Figure

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Chapter 27: Protists and the Dawn of the Eukarya Some Recurrent Body Forms Amoebas, which appear in many protist groups, move by means of pseudopods.Amoebas, which appear in many protist groups, move by means of pseudopods.54

Chapter 27: Protists and the Dawn of the Eukarya Some Recurrent Body Forms Actinopods have thin, stiff pseudopods that serve various functions, including food capture.Actinopods have thin, stiff pseudopods that serve various functions, including food capture.55

Chapter 27: Protists and the Dawn of the Eukarya Some Recurrent Body Forms Foraminiferans use pseudopods for feeding, and secrete shells of calcium carbonate.Foraminiferans use pseudopods for feeding, and secrete shells of calcium carbonate.56

Chapter 27: Protists and the Dawn of the Eukarya Some Recurrent Body Forms Acellular slime molds and cellular slime molds are superficially very similar.Acellular slime molds and cellular slime molds are superficially very similar. However, acellular slime molds are coenocytes with diploid nuclei.However, acellular slime molds are coenocytes with diploid nuclei. Cellular slime molds consist of individual haploid cells that form into masses of distinct cells.Cellular slime molds consist of individual haploid cells that form into masses of distinct cells.57