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The Protists
- Chapter 28
Lecture Objectives
1. Intro to “Protists”
2. Protist Classification
- Supergroups and Clades
3. Survey of Protists
Key Characteristics
1. Eukaryotic
2. Unicellular (mostly)  often colonial, or multicellular
3. Nutritionally Diverse
 Photoautotrophs, Heterotrophs, Mixotrophs
4.Reproduction
 Asexual (preferred) or Sexual
5. Worldwide distribution
 Sensitive to changes in environment (water, sun,
nutrients)
 Rely on nutrients from ocean floor (upwelling)
* being altered by humans (runoff, global warming)
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 Key Characteristics con’t.
6. Importance
 Symbionts
 Dinoflagellates & coral polyps, wood-digesting in gut of
termite
 Plasmodium sp. (Malaria) , Phytophthora sp. (SOD, potato
famine)
 Producers
 Along with prokaryotes  main producers in ocean
* responsible for ~30% world’s photosynthesis
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Other
consumers
Herbivorous
plankton
Prokaryotic
producers
Carnivorous
plankton
Protistan
producers
Figure 28.29
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Figure 28.28
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Protist Classification
Polyphyletic group = current classification includes distantly
related organisms, but does NOT include most recent common
ancestors of all members
• Kingdom “Protista” is no longer accepted  Grouped instead
into what are called Supergroups (possible new kingdoms?)
• Important to note this classification is still being sorted out
and we will consider one hypothesis…….
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4 Supergroups & respective clades
1. Excavata
2. SAR
3. Archaeplastida
4. Unikonta
■ Excavata
■ Archaeplastida
5 μm
20 μm
50 μm
Parabasalids
Euglenozoans
Excavata
Diplomonads
Stramenopiles
Diatoms
Golden algae
Brown algae
Apicomplexans
Ciliates
“SAR” clade
Alveolates
Dinoflagellates
■ “SAR” Clade
50 μm
■ Unikonta
Forams
Rhizarians
Cercozoans
Radiolarians
100 μm
Green
algae
Chlorophytes
Charophytes
Land plants
Tubulinids
Entamoebas
Opisthokonts
Fungi
Unikonta
Amoebozoans
100 μm
Slime molds
Nucleariids
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Archaeplastida
Red algae
Choanoflagellates
Animals
Figure 28.2
Supergroup Excavata:
- excavated “feeding” groove
- autotrophic or heterotrophic (predators)
Clade: Diplomonadida
Clade: Parabasala
Clade Euglenozoa
sub clade: Kinetoplastida
sub clade: Euglenophyta
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SG: Excavata, Clade: Diplomonadida
 Anaerobic
 Simplified mitochondria 
mitosomes
 2 equal sized nuclei
 Multiple Flagella
 Ex. Giardia
*Freshwater parasite in which
cyst stage is consumed. Causes
amoebic dysentery & killed by
boiling water.
Giardia sp.
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SG: Excavata, Clade: Parabasala
 Anaerobic, lack true nuclei
 Undulating membrane
 Flagella
 Modified mitochondria (release
Hydrogen Peroxide)
 change in pH
 outcompete beneficial
microorganisms
* Infection from gene
transfer with prokaryote
* Ex. Trichomonas vaginalis
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Trichomonas vaginalis
SG: Excavata, Clade Euglenozoa
 Flagella w/ crystalline rod
 Heterotrophs (predators),
Autotrophic, Parasites, or
Mixotrophs
 “Sub Clades”
 Kinetoplastida
* Cause of Sleeping Sickness
vectored by Tsetse fly
* Neurological disease which is
fatal if not treated
 Euglenophyta (see next slide)
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Trypanasoma sp.
Figure 28.8
* Note 2 flagella
Long flagellum
Eyespot
Short flagellum
Light
detector
Contractile vacuole
Nucleus
Chloroplast
Euglena (LM)
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5 μm
Plasma
membrane
Pellicle:
protein bands
beneath PM
Supergroup SAR
Clade: Stramenopila – flagella with hair-like projections
sub clade: Bacillariophyta
sub clade: Phaeophyta
sub clade: Chrysophyta
Clade: Alveolata – Membrane bound sacs under PM
sub clade: Dinoflagellata
sub clade: Apicomplexa
sub clade: Ciliophora
Clade Rhizaria – Amoeba with thread-like pseudopods
sub clade: Foraminifera
sub clade: Radiolaria
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Figure 28.9
Hairy
flagellum
Smooth
flagellum
5 μm
Supergroup SAR, Clade Stramenopile =
hairy flagella
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SG: SAR, Clade: Stramenopila,
sub-clade: Bacillariophyta
 The Diatoms
 Unicellular algae 




phytoplankton
MOST abundant autotroph
in oceans and lakes
Silica tests that overlap
Diatomaceous Earth
Help reduce C
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SG: SAR, Clade: Stramenopila,
sub-clade: Phaeophyta
 Brown algae (fucoxanthin)
 found in temperate coasts w/ cold





water currents
Largest, most complex algae 
multicellular
Tissues
Thallus (holdfast, stipe, blade) 
analogous to plants
Waves & desiccation = cell wall
with cellulose & algin
Alternation of Generations
Lifecycle
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Figure 28.13
Haploid (n)
Diploid (2n)
Sporangia
MEIOSIS
10 cm
Sporophyte
(2n)
Developing
sporophyte
Zygote
Mature female
(2n)
gametophyte
(n)
FERTILIZATION
Zoospore
Female
Gametophytes
(n)
Male
Egg
Sperm
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SG: SAR, Clade: Stramenopila,
sub-clade: Chrysophyta
 Golden Algae
 Unicellular, many colonial
 Bi-flagellated
 Fresh & marine phytoplankton,
(some mixotrophs)
 Yellow & brown pigments =
xanthophyll
 Microscopic & drift near surface of
water
 Protective cysts = decades
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Figure 28.14
Flagellum
Alveoli
0.2 μm
Alveolate
Supergroup SAR, Clade Alveolata =
Alveoli (sacs under PM)
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SG: SAR, Clade: Alveolata,
sub-clade: Dinoflagellata
 “Dinoflagellates”
 Marine & fresh phytoplankton
 Mixotrophs or heterotrophs
 Cellular plates of cellulose w/
grooves and 2 flagella
 Red Tides
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Figure 28.15
Flagella
(a) Dinoflagellate
flagella
3 μm
* May lead to mass mortalities
(b) Red tide in the Gulf
of Carpentaria in
northern Australia
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SG: SAR, Clade: Alveolata
sub-clade: Apicomplexa
 Apex on end of Merozoite
 Internal parasites to animals
 Malaria
vectored by mosquito
 hides in cells where it is
hidden from immune system
 Africa, Asia, Latin America
 250 million infected, 900,000
die each year
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Plasmodium sp.
Figure 28.16
Inside human
Inside mosquito
Sporozoites
(n)
Merozoite
Liver
Liver
cell
Apex
Oocyst
MEIOSIS
Zygote
(2n)
Merozoite
(n)
Red blood
cell
Red
blood
cells
FERTILIZATION
Gametes
Gametocytes
(n)
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Haploid (n)
Diploid (2n)
0.5 μm
SG: SAR, Clade: Alveolata,
sub-clade: Ciliophora
 “Ciliates”
 Cilia for locomotion & feeding
 Macro & micro nuclei (sex)
 Binary fission
 Found in all waters
 Predators or Parasitic
Paramecium sp.
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Figure 28.17a
Contractile
vacuole
50 μm
Cilia
Micronucleus
Macronucleus
(a) Feeding, waste removal, and water balance.
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Oral groove
Cell mouth
Food
vacuoles
Figure 28.17b-2
Compatible
mates
Conjugation
Asexual
reproduction
MEIOSIS
Diploid
micronucleus
The original macronucleus disintegrates.
Haploid
micronucleus
Diploid
micronucleus
MICRONUCLEAR
FUSION
(b) Conjugation and reproduction.
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SG: SAR, Clade: Rhizaria,
sub-clade: Foraminifera
 Marine, fresh water
 Attached to sand, rocks, algae
 Porous, multi-chambered shells




(CaCO3) = tests
Pseudopods extend through pores
* Phagocytosis
Many have endosymbiotic algae
Mg content = temp changes
Make sedimentary rocks
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SG: SAR, Clade: Rhizaria,
sub-clade: Radiolarians
 Delicate, symmetrical skeletons
made of silica
 Pseudopods radiate from central
body  engulf via phagocytosis
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