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Protists
Protists• Characteristics
• A) Organelles
• B) Organizational structure
Endosymbiotic hypothesis
Protists are believe to be the oldest eukaryotes on the evolutionary tree.
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Cyanobacterium
Heterotrophiceukaryote
Primaryendosymbiosis
Red algae
Green algae
Secondaryendosymbiosis
Secondaryendosymbiosis
Plastid
Dinoflagellates
Apicomplexans
Ciliates
Stramenopiles
Euglenids
Chlorarachniophytes
Plastid
Alve
olat
es
• Diversity of plastids produced by secondary endosymbiosis
Protists• Groups
• 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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Kingdom Protista is
very diverse.
15 phyla, based on the way
they obtain energy.
• Protist habitats are also diverse. • And including freshwater and marine species
100 µm
100 µm
4 cm
500 µm
The freshwater ciliate Stentor,a unicellular protozoan (LM)
Ceratium tripos, a unicellular marine dinoflagellate (LM)
Delesseria sanguinea, a multicellular marine red alga
Spirogyra, a filamentous freshwater green alga (inset LM)
(a)
(b)
(c)
(d)
LE 16-19
Dip
lom
onad
s
Eugl
enoz
oans
Din
ofla
gella
tes
Api
com
plex
ans
Cili
ates
Wat
er m
olds
Bro
wn
alga
e
Gre
en a
lgae
Plan
ts
Clo
sest
alg
al re
lativ
es o
f pla
nts
Red
alg
ae
Ani
mal
s
Fung
i
Am
oeba
s
Cho
anof
lage
llate
s
Cel
lula
r slim
e m
olds
Plas
mod
ials
lime
mol
ds
Dia
tom
s
Alveolates Stramenopila Amoebozoa
Ancestral eukaryote
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Fig. 22-2, p.352
Groups (Phyla)
7 monophyletic groups
Parabasalids & Diplomonads
• Most primitive• Are adapted to anaerobic environments• Lack plastids• Have mitochondria that lack DNA, an
electron transport chain, or citric-acid cycle enzymes
Diplomonads• Diplomonads
– Have two nuclei and multiple flagella
5 µm(a) Giardia intestinalis, a diplomonad (colorized SEM)
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Once ingested by a host, the trophozoiteemerges to an active state of feeding and motility. It feeds on mucous inside the digestive tract and causes the host to have epigastric pain, excessive gas, and diarrhea with fat and mucous but no blood. This can last from 2 -4 weeks but for a lactose intolerant individual, it can last up to six months.
Diplomonads – 3+1 flagella
Giardia lamblia – intestinal parasite
Fig. 22-3b,c p.353
Parabasalids• Parabasalids include trichomonads
– Which move by means of flagella and an undulating part of the plasma membrane
Trichomonas vaginalis, a parabasalid (colorized SEM)
Flagella
Undulating membrane 5 µm
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Parabasalids--Heterotrophic flagellates
Trichomonas vaginalis
Fig. 22-3a, p.353
STD
Euglenoids & Kinetoplastids
• Single-celled flagellates• Have flagella with a unique internal
structure• A diverse clade that includes
– Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites
• The main feature that distinguishes protists in this clade– Is the presence of a spiral or crystalline rod
of unknown function inside their flagella
Flagella 0.2 µm
Crystalline rod
Ring of microtubules
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Fig. 22-4b, p.354
Euglenoids
Euglena gracilis
mitochondrion
nucleus
long flagellum
chloroplast
Fig. 22-4a2, p.354
Euglenoids
Euglena gracilis
Phylum Euglenophyta
Freshwater
This phylum is a typical example of the difficulties in categorizing protists: 1/3 have chloroplasts, the other 2/3 do not.
No sexual reproduction. Longitudinal fission.
Propels the body through water.
For photosynthesis
Diversity of Kingdom Protista
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Kinetoplastids
• Kinetoplastids– Have a single, large mitochondrion that
contains an organized mass of DNA called a kinetoplast
– Include free-living consumers of bacteria in freshwater, marine, and moist terrestrial ecosystems
– Known best for its parasitic representatives
long flagellum attached to undulating membrane
single, longmitochondrion
Golgi body
vacuolenucleusER
Fig. 22-5a, p.355
Kinetoplastids -- Heterotrophs (parasites)
Fig. 22-5b, p.355
red blood cellundulating membrane attached to flagellum
Trypanosoma brucei --- sleeping sickness
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Trypanosomes- transmitted by the bite of a tsetse fly,
cause African Sleeping Sickness.
9 µm
Trypanosoma transferred by
Triatomine bugs (kissing bugs)
causes South American Chagas disease
Forams & Radiolarians
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Fig. 22-6, p.355
Forams & Radiolarians
Part of marine plankton
Foraminiferans (Forams)• Foraminiferans, or forams
– Are named for their porous, generally multichambered shells, called tests
20 µm
Foraminiferans (Forams)
• Pseudopodia extend through the pores in the test
• Foram tests in marine sediments– Form an extensive fossil record
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Radiolarians
• Radiolarians are marine protists….– whose tests are fused into one delicate
piece, which is generally made of silica– that phagocytose microorganisms with their
pseudopodia
• The pseudopodia of radiolarians, known as axopodia– Radiate from the central body
200 µm
Axopodia
Alveolates
Cillium/flagellumAlveoli0.2 µm
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Ciliated Alveolates
alveolus
cilium
Ciliates
• Ciliates, a large varied group of protists– Are named for their use of cilia to move and
feed– Have large macronuclei and small
micronuclei
Paramecium
Paramecium
Didinium
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food vacuole (being emptied)
gullet
cilia trichocysts
filled contractile vacuole
micronucleus
macronucleus
contractile vacuole emptied
Fig. 22-7c, p.356
Paramecium
intact trichocyst
Fig. 22-7a2, p.356
contractile vacuole
pellicle
Paramecium
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micronucleus
macronucleus
Fig. 22-7c, p.356
Paramecium
Fig. 22-8, p.357
Fig. 22-8n, p.357
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Flagellated Alveolates
• Dinoflagellates
Dinoflagellates
• Dinoflagellates– Are a diverse group of aquatic
photoautotrophs and heterotrophs– Are abundant components of both marine
and freshwater phytoplankton
Flagellated Alveolates• Dinoflagellates
Some are bioluminescent Some produce toxins
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