chapter 27 protists and the dawn of the eukarya

Chapter 27: Protists and the Dawn of the Eukarya

CHAPTER 27Protists and the Dawn

of the Eukarya


Chapter 27: Protists and the Dawn of the EukaryaProtistsProtists Defined Defined

The Origin of the Eukaryotic CellThe Origin of the Eukaryotic Cell

General Biology of the General Biology of the ProtistsProtists

ProtistProtist Diversity Diversity


Chapter 27: Protists and the Dawn of the EukaryaEuglenozoaEuglenozoa

AlveolataAlveolata

StramenopilaStramenopila

RhodophytaRhodophyta


Chapter 27: Protists and the Dawn of the EukaryaChlorophytaChlorophyta

ChoanoflagellidaChoanoflagellida

A History of EndosymbiosisA History of Endosymbiosis

Some Recurrent Body FormsSome Recurrent Body Forms


Protists Defined

• In this book we define the protists as In this book we define the protists as all eukaryotes that are not plants, all eukaryotes that are not plants, fungi, or animals. fungi, or animals.

• They are not a monophyletic group.They are not a monophyletic group.

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The Origin of the Eukaryotic Cell• The modern eukaryotic cell arose from The modern eukaryotic cell arose from

an ancestral prokaryote. an ancestral prokaryote.

• Probable steps included loss of the cell Probable steps included loss of the cell wall and inward folding of the plasma wall and inward folding of the plasma membrane. membrane.

Review Figure 27.2Review Figure 27.2

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Figure 27.2

Figure 27.2Figure 27.2

figure 27-02.jpg


The Origin of the Eukaryotic Cell

• An infolded plasma membrane An infolded plasma membrane attached to the chromosome may attached to the chromosome may have led to formation of a nuclear have led to formation of a nuclear envelope. envelope.

• A primitive cytoskeleton evolved. A primitive cytoskeleton evolved.


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Figure 27.3 – Part 1

Figure 27.3 – Part 1Figure 27.3 – Part 1

figure 27-03a.jpg


Figure 27.3 – Part 2

Figure 27.3 – Part Figure 27.3 – Part 22

figure 27-03b.jpg


The Origin of the Eukaryotic Cell

• The first truly eukaryotic cell was The first truly eukaryotic cell was larger than its prokaryote ancestor, larger than its prokaryote ancestor, and possibly possessed one or more and possibly possessed one or more eukaryotic type flagella.eukaryotic type flagella.

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The Origin of the Eukaryotic Cell • Prokaryotic cells incorporated as Prokaryotic cells incorporated as

endosymbionts gave rise to eukaryotic endosymbionts gave rise to eukaryotic organelles. organelles.

• Peroxisomes may have been the first Peroxisomes may have been the first organelles of endosymbiotic origin. organelles of endosymbiotic origin.

• Mitochondria evolved from Mitochondria evolved from proteobacteria, proteobacteria,

• Chloroplasts from cyanobacteria. Chloroplasts from cyanobacteria. • Cells with nuclei probably appeared Cells with nuclei probably appeared

before those with mitochondria. before those with mitochondria.


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General Biology of the Protists

• Most protists are aquatic; some live Most protists are aquatic; some live within other organisms. within other organisms.

• The great majority are unicellular and The great majority are unicellular and microscopic but, many are microscopic but, many are multicellular and a few are enormous.multicellular and a few are enormous.

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• ““Protozoan” is an outdated term Protozoan” is an outdated term applied to protists once classified as applied to protists once classified as animals. animals.

• ““Alga” is an outdated term applied to Alga” is an outdated term applied to photosynthetic protists.photosynthetic protists.

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• Protists vary in modes of nutrition, Protists vary in modes of nutrition, metabolism, and locomotion. metabolism, and locomotion.

• Some protist cells contain contractile Some protist cells contain contractile vacuoles, some digest food in food vacuoles, some digest food in food vacuoles. vacuoles.

Review Figures 27.5, 27.6Review Figures 27.5, 27.6

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Figure 27.5


figure 27-05.jpg


Figure 27.6


figure 27-06.jpg



• Protists have a variety of cell surfaces, Protists have a variety of cell surfaces, some of them protective.some of them protective.

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• Many protists contain endosymbiotic Many protists contain endosymbiotic prokaryotes. prokaryotes.

• Some are endosymbiotic in other cells, Some are endosymbiotic in other cells, including other protists. including other protists.

• Some endosymbiotic protists perform Some endosymbiotic protists perform photosynthesis.photosynthesis.

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• Most protists reproduce both asexually Most protists reproduce both asexually and sexually.and sexually.

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Protist Diversity

• Molecular and other techniques are Molecular and other techniques are enabling biologists to identify many enabling biologists to identify many monophyletic groups of protists. monophyletic groups of protists.

Review Figure 27.9, Table 27.1Review Figure 27.9, Table 27.1

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Figure 27.9


figure 27-09.jpg


Table 27.1

Table 27.1Table 27.1

table 27-01.jpg


Euglenozoa

• The Euglenozoa are a monophyletic The Euglenozoa are a monophyletic group of unicellular protists with group of unicellular protists with flagella.flagella.

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Euglenozoa

• Euglenoids are Euglenozoa that are Euglenoids are Euglenozoa that are often photosynthetic and have anterior often photosynthetic and have anterior flagella.flagella.

See figure 10See figure 10


Euglenozoa

• Kinetoplastids are Euglenozoa that Kinetoplastids are Euglenozoa that have a single, large mitochondrion, in have a single, large mitochondrion, in which RNA is edited.which RNA is edited.

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Alveolata

• The Alveolata are a monophyletic The Alveolata are a monophyletic group of unicellular organisms with group of unicellular organisms with alveoli beneath their plasma alveoli beneath their plasma membranes.membranes.

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Alveolata

• Dinoflagellates are marine alveolates Dinoflagellates are marine alveolates with a unique color. with a unique color.

• They are major contributors to world They are major contributors to world photosynthesis. photosynthesis.

• Many are endosymbionts; they Many are endosymbionts; they contribute to coral reef growth. contribute to coral reef growth.

• Dinoflagellates cause“red tides.”Dinoflagellates cause“red tides.”2828


Alveolata

• Apicomplexans are parasitic alveolates. Apicomplexans are parasitic alveolates.

• Their spores, containing a mass of Their spores, containing a mass of organelles, are adapted to the invasion organelles, are adapted to the invasion of host tissue. of host tissue.

• The apicomplexan Plasmodium causes The apicomplexan Plasmodium causes malaria. malaria.



Figure 27.13


figure 27-13.jpg


Alveolata

• Ciliates are alveolates that move via Ciliates are alveolates that move via cilia and have two kinds of nuclei. cilia and have two kinds of nuclei.

• The macronuclei control the cell with The macronuclei control the cell with transcription and translation,and are transcription and translation,and are responsible for genetic recombination responsible for genetic recombination by conjugation. by conjugation.

• Some ciliates have a complex internal Some ciliates have a complex internal structure. structure.

Review Figures 27.15, 27.16, 27.17Review Figures 27.15, 27.16, 27.173131


Figure 27.15


figure 27-15.jpg


Figure 27.16


figure 27-16.jpg


Figure 27.17 – Part 1Figure 27.17 – Part 1Figure 27.17 – Part 1

figure 27-17a.jpg


Figure 27.17 – Part 2Figure 27.17 – Part 2Figure 27.17 – Part 2

figure 27-17b.jpg


Stramenopila

• Stramenopiles typically have two Stramenopiles typically have two flagella of unequal length, the longer flagella of unequal length, the longer bearing rows of tubular hairs. bearing rows of tubular hairs.

• Some groups are photosynthetic.Some groups are photosynthetic.

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Stramenopila

• Diatoms are unicellular stramenopiles, Diatoms are unicellular stramenopiles, many of which have complex, two-many of which have complex, two-part, glassy cell walls. part, glassy cell walls.

• They contribute to world They contribute to world photosynthesis. photosynthesis.


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Figure 27.19


figure 27-19.jpg


Stramenopila

• The brown algae are predominantly The brown algae are predominantly multicellular, photosynthetic multicellular, photosynthetic stramenopiles. stramenopiles.

• They include the largest of all protists. They include the largest of all protists.

• Some show considerable tissue Some show considerable tissue differentiation.differentiation.

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Stramenopila

• In many multicellular photosynthetic In many multicellular photosynthetic protists and all plants, haploid and diploid protists and all plants, haploid and diploid cells undergo mitosis and alternation of cells undergo mitosis and alternation of generations. generations.

• The diploid sporophyte generation forms The diploid sporophyte generation forms spores by meiosis which become haploid. spores by meiosis which become haploid.

• The haploid gametophyte generation The haploid gametophyte generation forms gametes by mitosis and yields forms gametes by mitosis and yields zygotes: the next generation of zygotes: the next generation of sporophytes. sporophytes.


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Figure 27.22


figure 27-22.jpg


Stramenopila

• Oomycetes are a group of Oomycetes are a group of nonphotosynthetic stramenopiles .nonphotosynthetic stramenopiles .

• The oomycetes are coenocytic. The oomycetes are coenocytic.

• They are diploid for most of their life They are diploid for most of their life cycle.cycle.

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Rhodophyta

• Red algae (Rhodophyta) are Red algae (Rhodophyta) are multicellular, photosynthetic protists multicellular, photosynthetic protists that have a characteristic storage that have a characteristic storage product (floridean starch) and lack product (floridean starch) and lack flagellated reproductive cells.flagellated reproductive cells.

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Chlorophyta

• The Chlorophyta are often The Chlorophyta are often multicellular, contain chlorophylls a multicellular, contain chlorophylls a and b, and use starch as a storage and b, and use starch as a storage product. product.

• Their life cycles include the isomorphic Their life cycles include the isomorphic alternation of generations of Ulva and alternation of generations of Ulva and the haplontic life cycle of Ulothrix. the haplontic life cycle of Ulothrix.

Review Figures 27.26, 27.27Review Figures 27.26, 27.27

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Figure 27.26


figure 27-26.jpg


Figure 27.27


figure 27-27.jpg


Chlorophyta

• The chlorophytes are sister to a The chlorophytes are sister to a lineage including other green algae lineage including other green algae and the plant kingdom.and the plant kingdom.

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Choanoflagellida

• The Choanoflagellida are protists with The Choanoflagellida are protists with flagella and a body type similar to a flagella and a body type similar to a characteristic type of sponge cell. characteristic type of sponge cell.

• The Choanoflagellida are sister to the The Choanoflagellida are sister to the animal kingdom. animal kingdom.

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A History of Endosymbiosis• Primary endosymbiosis of a Primary endosymbiosis of a

cyanobacterium and a eukaryote gave cyanobacterium and a eukaryote gave rise to the chloroplasts of green algae, rise to the chloroplasts of green algae, plants, and red algae. plants, and red algae.


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Figure 27.29


figure 27-29.jpg


A History of Endosymbiosis • Secondary endosymbiosis of Secondary endosymbiosis of

eukaryotes with unicellular green or eukaryotes with unicellular green or red algae gave rise to the chloroplasts red algae gave rise to the chloroplasts of euglenoids, stramenopiles, and of euglenoids, stramenopiles, and other groups. other groups.

• A cell of one of those groups, in A cell of one of those groups, in tertiary endosymbiosis, gave rise to tertiary endosymbiosis, gave rise to another type of chloroplast.another type of chloroplast.

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Some Recurrent Body Forms• Some similar body forms are found in Some similar body forms are found in

several different, unrelated protist several different, unrelated protist groups. groups.


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Figure 27.30


figure 27-30.jpg


Some Recurrent Body Forms • Amoebas, which appear in many Amoebas, which appear in many

protist groups, move by means of protist groups, move by means of pseudopods.pseudopods.

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Some Recurrent Body Forms • Actinopods have thin, stiff pseudopods Actinopods have thin, stiff pseudopods

that serve various functions, including that serve various functions, including food capture.food capture.

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Some Recurrent Body Forms • Foraminiferans use pseudopods for Foraminiferans use pseudopods for

feeding, and secrete shells of calcium feeding, and secrete shells of calcium carbonate.carbonate.

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Some Recurrent Body Forms • Acellular slime molds and cellular Acellular slime molds and cellular

slime molds are superficially very slime molds are superficially very similar. similar.

• However, acellular slime molds are However, acellular slime molds are coenocytes with diploid nuclei. coenocytes with diploid nuclei.

• Cellular slime molds consist of Cellular slime molds consist of individual haploid cells that form into individual haploid cells that form into masses of distinct cells.masses of distinct cells.

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chapter 27 protists and the dawn of the eukarya

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