Campbell Biology 8ed

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

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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Protista is no longer valid as a kingdom

3. Fig. 28-01
1 µm

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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

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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

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• 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

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• Protists can reproduce asexually or sexually, or
by the sexual processes of meiosis and
syngamy

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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

9. Fig. 28-02-1
1 µm
Cyanobacterium
terotrophic
karyote
Over the course
of evolution,
this membrane
was lost.
Red alga
Green alga
Primary
endosymbiosis

10. Fig. 28-02-2
Cyanobacterium
terotrophic
karyote
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

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• 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

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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
AmoebozoansOpisthokontsAlveolatesStramenopiles
Diplomonads
Parabasalids
Euglenozoans
Dinoflagellates
Apicomplexans
Ciliates
Diatoms
Golden algae
Brown algae
Oomycetes
ExcavataChromalveolataRhizaria
Chlorarachniophytes
Forams
Radiolarians
Archaeplastida
Red algae
Chlorophytes
Charophyceans
Land plants
Unikonta
Slime molds
Gymnamoebas
Entamoebas
Nucleariids
Fungi
Choanoflagellates
Animals

14. Fig. 28-03b
Diplomonads
Parabasalids
Euglenozoans
Excavata

15. Fig. 28-03c
AlveolatesStramenopiles
Dinoflagellates
Apicomplexans
Ciliates
Diatoms
Golden algae
Brown algae
Oomycetes
Chromalveolata

16. Fig. 28-03d
Chlorarachniophytes
Forams
Radiolarians
Rhizaria

17. Fig. 28-03e
Red algae
Chlorophytes
Charophyceans
Land plants
Green
algae
Archaeplastida

18. Fig. 28-03f
Choanoflagellates
Animals
Fungi
Gymnamoebas
Entamoebas
Nucleariids
Unikonta
Slime molds
AmoebozoansOpisthokonts

19. Fig. 28-03g
5 µm

20. Fig. 28-03h
50 µm

21. Fig. 28-03i
20 µm

22. Fig. 28-03j
20 µm
50 µm

23. Fig. 28-03l
100 µm

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• 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

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Fig. 28-UN1
Kinetoplastids
Euglenids
Diplomonads
Parabasalids
Euglenozoans
Excavata
Chromalveolata
Rhizaria
Archaeplastida
Unikonta

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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

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• Parabasalids
– Have reduced mitochondria called
hydrogenosomes that generate some energy
anaerobically
– Include Trichomonas vaginalis, the pathogen
that causes yeast infections in human females

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

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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

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

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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

32. Fig. 28-06
9 µm

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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:Video: EuglenaEuglena
Video:Video: EuglenaEuglena MotionMotion

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

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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

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Fig. 28-UN2
Dinoflagellates
Apicomplexans
Ciliates
Diatoms
Golden algae
Brown algae
Oomycetes
Rhizaria
Archaeplastida
Unikonta
Chromalveolata
Excavata
Alveolates
Stramenopiles

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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

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

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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: DinoflagellateVideo: Dinoflagellate

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• Two flagella make them spin as they move
through the water
• Dinoflagellate blooms are the cause of toxic
“red tides”

41. Fig. 28-09
Flagella
3µm

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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

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• 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

44. 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

45. 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

46. 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)

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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

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
Conjugation
Reproduction

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

50. Fig. 28-11b-1
ompatible
ates
Diploid
micronucleus
MEIOSIS
Haploid
micronucleus
Key
Conjugation
Reproduction
(b) Conjugation and reproduction

51. Fig. 28-11b-2
ompatible
ates
Diploid
micronucleus
MEIOSIS
Haploid
micronucleus
Key
Conjugation
Reproduction
(b) Conjugation and reproduction
Diploid
micronucleus
MICRONUCLEAR
FUSION
The original
macronucleus
disintegrates.

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Video:Video: VorticellaVorticella HabitatHabitat
Video:Video: VorticellaVorticella DetailDetail
Video:Video: VorticellaVorticella CiliaCilia
Video:Video: ParameciumParamecium VacuoleVacuole
Video:Video: ParameciumParamecium CiliaCilia

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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

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

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Diatoms
• Diatoms are unicellular algae with a unique
two-part, glass-like wall of hydrated silica
• Diatoms usually reproduce asexually, and
occasionally sexually

56. Fig. 28-13
3µm

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• 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 DiatomsVideo: Various Diatoms
Video: Diatoms MovingVideo: Diatoms Moving

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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

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

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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

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• 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

62. Fig. 28-15
Blade
Stipe
Holdfast

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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

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

65. 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)

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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

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

68. 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

69. 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

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Video: Water Mold OogoniumVideo: Water Mold Oogonium
Video: Water Mold ZoosporesVideo: Water Mold Zoospores

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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

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Fig. 28-UN3
Chlorarachniophytes
Foraminiferans
Radiolarians
Excavata
Chromalveolata
Archaeplastida
Unikonta
Rhizaria

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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

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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

75. Fig. 28-18
Pseudopodia
200 µm

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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

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Fig. 28-UN4
Chlorophytes
Charophyceans
Red algae
Green algae
Land plants
Excavata
Chromalveolata
Rhizaria
Archaeplastida
Unikonta

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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

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. Fig. 28-19a
Bonnemaisonia
hamifera
8 mm

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

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.

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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

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• Most chlorophytes live in fresh water, although
many are marine
• Other chlorophytes live in damp soil, as
symbionts in lichens, or in snow

85. Fig. 28-20

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• Chlorophytes include unicellular, colonial, and
multicellular forms
Video:Video: VolvoxVolvox Female SpheroidFemale Spheroid
Video:Video: VolvoxVolvox DaughterDaughter
Video:Video: VolvoxVolvox ColonyColony
Video:Video: VolvoxVolvox FlagellaFlagella
Video:Video: VolvoxVolvox Inversion 1Inversion 1
Video:Video: VolvoxVolvox Inversion 2Inversion 2
Video:Video: VolvoxVolvox Sperm and FemaleSperm and Female

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

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

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

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• Most chlorophytes have complex life cycles
with both sexual and asexual reproductive
stages
Video:Video: ChlamydomonasChlamydomonas

91. Fig. 28-22-1
1 µmFlagella
Cell wall
Nucleus
Cross
section of
cup-shaped
chloroplast
Mature cell
(n)
Zoospore
ASEXUAL
REPRODUCTION
Haploid (n)
Diploid (2n)
Key

92. Fig. 28-22-2
1 µmFlagella
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
+
+
–
–

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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

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

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

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Amoebozoans
• Amoebozoans are amoeba that have lobe- or
tube-shaped, rather than threadlike,
pseudopodia
• They include gymnamoebas, entamoebas, and
slime molds

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Slime Molds
• Slime molds, or mycetozoans, were once
thought to be fungi
• Molecular systematics places slime molds in
the clade Amoebozoa

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Plasmodial Slime Molds
• Many species of plasmodial slime molds are
brightly pigmented, usually yellow or orange
Video: Plasmodial Slime Mold StreamingVideo: Plasmodial Slime Mold Streaming
Video: Plasmodial Slime MoldVideo: Plasmodial Slime Mold

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 (2n)

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 (2n)
MEIOSIS
Spores
(n)
Germinating
spore
Amoeboid cells
(n)
Flagellated
cells
(n)

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 (2n)
MEIOSIS
Spores
(n)
Germinating
spore
Amoeboid cells
(n)
Flagellated
cells
(n)
Zygote
(2n)
FERTILIZATION

102. 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

103. 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

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 (2n)

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

106. 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 PseudopodiaVideo: Amoeba Pseudopodia
Video: AmoebaVideo: Amoeba

107. 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

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

109. 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

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

111. Fig. 28-26
0µm

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

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. 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

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

116. Fig. 28-UN6

117. Fig. 28-UN6a

118. Fig. 28-UN6b

119. Fig. 28-UN6c

120. Fig. 28-UN6d

121. Fig. 28-UN6e

122. Fig. 28-UN7

123. Fig. 28-UN8

124. 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