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ProtistsProtists
Chapter 25Chapter 25
Learning Objective 1Learning Objective 1
• What features are common to the What features are common to the members of kingdom Protista?members of kingdom Protista?
ProtistsProtists
• Mostly unicellular eukaryotic organisms Mostly unicellular eukaryotic organisms that live in aquatic environmentsthat live in aquatic environments
Sizes of ProtistsSizes of Protists
• UnicellularUnicellular organisms organisms• microscopicmicroscopic
• ColoniesColonies• loosely connected groups of cells loosely connected groups of cells
• CoenocytesCoenocytes• multinucleate masses of cytoplasm multinucleate masses of cytoplasm
• MulticellularMulticellular organisms organisms• composed of many cellscomposed of many cells
ChlamydomonasChlamydomonas
• A unicellular protistA unicellular protist
Fig. 25-1, p. 531
Flagella
Cell wall
Nucleus
Chloroplast
Starch granule
KEY CONCEPTSKEY CONCEPTS
• Protists are a diverse group of eukaryotic Protists are a diverse group of eukaryotic organisms, most of which are microscopicorganisms, most of which are microscopic
Learning Objective 2Learning Objective 2
• Discuss in general terms the diversity Discuss in general terms the diversity inherent in the protist kingdominherent in the protist kingdom• means of locomotionmeans of locomotion• modes of nutritionmodes of nutrition• interactions with other organismsinteractions with other organisms• habitatshabitats• modes of reproductionmodes of reproduction
LocomotionLocomotion
• PseudopodiaPseudopodia• FlagellaFlagella• CiliaCilia• Some are nonmotileSome are nonmotile
NutritionNutrition
• Protists obtain their nutrients Protists obtain their nutrients autotrophicallyautotrophically or or heterotrophicallyheterotrophically
InteractionsInteractions
• Protists are free-living or symbioticProtists are free-living or symbiotic
• Symbiotic relationships range from Symbiotic relationships range from mutualismmutualism to to parasitismparasitism
HabitatsHabitats
• Most protists live inMost protists live in• oceanocean• freshwater pondsfreshwater ponds• lakeslakes• streamsstreams
• Parasitic protists live in body fluids of hostsParasitic protists live in body fluids of hosts
ReproductionReproduction
• Many protists reproduce both sexually and Many protists reproduce both sexually and asexually asexually
• Others reproduce only asexuallyOthers reproduce only asexually
KEY CONCEPTSKEY CONCEPTS
• Protists vary in body plan (unicellular, Protists vary in body plan (unicellular, colonial, coenocytic, multicellular), method colonial, coenocytic, multicellular), method of motility (pseudopodia, cilia, flagella), of motility (pseudopodia, cilia, flagella), nutrition type (autotrophic, heterotrophic), nutrition type (autotrophic, heterotrophic), and mode of reproduction (asexual, and mode of reproduction (asexual, sexual)sexual)
Learning Objective 3Learning Objective 3
• What is the hypothesis of What is the hypothesis of serial serial endosymbiosisendosymbiosis??
• Explain some evidence that supports itExplain some evidence that supports it
Serial EndosymbiosisSerial Endosymbiosis
• Hypothesis:Hypothesis:• MitochondriaMitochondria and and chloroplastschloroplasts arose from arose from
symbiotic relationships between larger cells symbiotic relationships between larger cells and smaller prokaryotes that were and smaller prokaryotes that were incorporated and lived within themincorporated and lived within them
MitochondriaMitochondria
• Probably originated from aerobic bacteriaProbably originated from aerobic bacteria
• Ribosomal RNA data suggestsRibosomal RNA data suggests
• ancient purple bacteria were ancestors of ancient purple bacteria were ancestors of mitochondriamitochondria
ChloroplastsChloroplasts
• Single primary endosymbiotic event Single primary endosymbiotic event • in red algae, green algae, and plantsin red algae, green algae, and plants• cyanobacterium incorporated into a cellcyanobacterium incorporated into a cell
• Multiple secondary endosymbiosesMultiple secondary endosymbioses• in euglenoids, dinoflagellates, diatoms, golden in euglenoids, dinoflagellates, diatoms, golden
algae, brown algaealgae, brown algae• nonfunctional chloroplasts in apicomplexansnonfunctional chloroplasts in apicomplexans
Chloroplast Chloroplast EvolutionEvolution
Fig. 25-2a, p. 532
Mitochondrion
Nucleus
Eukaryotic cell with mitochondria
Bacterial DNA
Cyanobacterium (ancestor of chloroplast)
(a) Primary endosymbiosis
Fig. 25-2b, p. 532
Eukaryotic cell with mitochondria
Chloroplast DNA
Chloroplast with two membranes
Eukaryotic cell with mitochondria and
chloroplasts (red alga)
Chloroplast with three membranes
Eukaryotic cell with mitochondria and
chloroplasts (dinoflagellate?)
(b) Secondary endosymbiosis
Stepped Art
Fig. 25-2b, p. 532
Chloroplast with three membranes
Eukaryotic cell with mitochondria and chloroplasts (dinoflagellate?)
(b) Secondary endosymbiosis
Eukaryotic cell with mitochondria
Chloroplast DNA
Chloroplast with two membranes
Eukaryotic cell with mitochondria and chloroplasts (red alga)
(a) Primary endosymbiosis Cyanobacterium
(ancestor of chloroplast)
Bacterial DNA
Eukaryotic cell with mitochondria
Mitochondrion
Nucleus
Learning Objective 4Learning Objective 4
• What kinds of data do biologists use to What kinds of data do biologists use to classify eukaryotes?classify eukaryotes?
Relationships Among ProtistsRelationships Among Protists
• Protist kingdomProtist kingdom• paraphyleticparaphyletic group group
• Determined byDetermined by• ultrastructure ultrastructure ((electron microscopy)electron microscopy)• comparative molecular datacomparative molecular data
Eukaryote PhylaEukaryote Phyla
Fig. 25-3, p. 533
Lan
d p
lan
ts
Am
oe
bas
Pla
smo
dia
lsl
ime
mo
lds
Cel
lula
r
slim
e m
old
s
An
imal
s
Fu
ng
i
Zo
ofl
agel
late
s (d
iplo
mo
nad
s)
Zo
ofl
agel
late
s (e
ug
len
oid
s)
Ap
ico
mp
lexa
ns
Cil
iate
s
Wat
er m
old
s
Bro
wn
alg
ae
Red
alg
ae
Gre
en a
lgae
A
Ancestral eukaryote
Eukaryote CladesEukaryote Clades
Fig. 25-4, p. 535
Pla
nts
Exc
avat
es
Dis
cic
rist
ate
s
Alv
eo
late
s
Het
ero
ko
nts
Cer
cozo
a
Am
oe
bo
zoa
Op
isth
oko
nts
Lan
d p
lan
ts
Fo
ram
inif
era
ns
and
act
ino
po
ds
Am
oe
bas
Pla
smo
dia
l sl
ime
mo
lds
Cel
lula
r sl
ime
mo
lds
An
imal
s
Fu
ng
i
Zo
ofl
agel
late
s (d
iplo
mo
nad
s)
Zo
ofl
agel
late
s,
(eu
gle
no
ids)
Ap
ico
mp
lexa
ns
Cil
iate
s
Wat
er m
old
s
Bro
wn
alg
ae
Red
alg
ae
Gre
en a
lgae
?
Ancestral eukaryote
KEY CONCEPTSKEY CONCEPTS
• Protists are descendants of early Protists are descendants of early eukaryoteseukaryotes
Learning Objective 5Learning Objective 5
• Why are Why are zooflagellateszooflagellates no longer classified no longer classified in a single phylum?in a single phylum?
• Distinguish among Distinguish among diplomonadsdiplomonads, , euglenoidseuglenoids, and , and choanoflagellateschoanoflagellates
ZooflagellatesZooflagellates
• Mostly unicellular heterotrophsMostly unicellular heterotrophs
• Move by whiplike Move by whiplike flagellaflagella
• PolyphyleticPolyphyletic• separated into several monophyletic groupsseparated into several monophyletic groups
DiplomonadsDiplomonads
• DiplomonadsDiplomonads are are excavatesexcavates• with a deep (excavated) oral groovewith a deep (excavated) oral groove
• Diplomonads haveDiplomonads have• one or two nucleione or two nuclei• no mitochondriano mitochondria• no Golgi complexno Golgi complex• up to eight flagellaup to eight flagella
ExcavatesExcavates
Fig. 25-5b, p. 536
Nucleus
Flagella
50 µm
EuglenoidsEuglenoids
• EuglenoidsEuglenoids are are discicristatesdiscicristates• with disclike cristae in mitochondriawith disclike cristae in mitochondria
• EuglenoidsEuglenoids• are unicellular and flagellateare unicellular and flagellate• some are photosynthetic some are photosynthetic
• TrypanosomaTrypanosoma• causes African sleeping sicknesscauses African sleeping sickness
DiscicristatesDiscicristates
Fig. 25-6a, p. 537
Flagellum for locomotionEyespot
Contractile vacuole
Chloroplast
Nucleus
Paramylon body (stored food)
Pellicle
25 µm
Fig. 25-6b, p. 537
Flagellum for locomotion
Nonemergent flagellum (indistinguishable in
micrograph)
EyespotContractile vacuole
Mitochondria (indistinguishable
in micrograph)
ChloroplastNucleolus
Nucleus
Paramylon body (stored food)
Chromatin
Pellicle
Fig. 25-6c, p. 537
Red blood cells
Trypanosome with undulating membrane
Flagellum
25 µm
ChoanoflagellatesChoanoflagellates
• ChoanoflagellatesChoanoflagellates are are opisthokontsopisthokonts• single posterior flagellum in flagellate cells single posterior flagellum in flagellate cells • collar of microvilli surrounds base of flagellum collar of microvilli surrounds base of flagellum
• ChoanoflagellatesChoanoflagellates• are related to fungi and animals are related to fungi and animals
ChoanoflagellateChoanoflagellate
Fig. 25-25, p. 551
Flagellum
Collar of microvilli
CellLorica (protective cover)
Stalk
Learning Objective 6Learning Objective 6
• Describe and compare these Describe and compare these alveolatesalveolates: : • ciliatesciliates• dinoflagellatesdinoflagellates• apicomplexansapicomplexans
CiliatesCiliates
• AlveolatesAlveolates• move by hairlike move by hairlike ciliacilia • micronucleimicronuclei (for sexual reproduction) (for sexual reproduction)• macronucleimacronuclei (for cell metabolism and growth) (for cell metabolism and growth)• undergo complex sexual reproduction undergo complex sexual reproduction
(conjugation)(conjugation)
CiliatesCiliates
Fig. 25-7a, p. 538
Cilia
Food vacuoles
Micronucleus
Macronucleus
Contractile vacuole
50 µm
Fig. 25-7b, p. 538
Cilia
Food vacuoles
Food
Micronucleus
Oral grooveMacronucleus
Contractile vacuole
Anal pore Food vacuole
Fig. 25-7c, p. 538
Cytopharynx
Macronucleus
250 µm
Fig. 25-7d, p. 538
Cirri
ConjugationConjugation
Fig. 25-8, p. 539
Disintegrating macronucleiMacronuclei
Diploid nuclei (2n)
Micronuclei (2n) Disintegrating micronuclei
Two sexually compatible
individuals join at oral surfaces
First meiotic division in each cell
Second meiotic
division in each cell
One haploid micronucleus
divides by mitosis; others
disintegrate
Each conjugating
cell exchanges
micronucleus
Haploid micronuclei
fuse
Cells separate
1
2
3
4
5
6
7
Insert “Ciliate Insert “Ciliate conjugation”conjugation”
ciliate_conjugation.swfciliate_conjugation.swf
Watch conjugation by clicking Watch conjugation by clicking on the figure in ThomsonNOW.on the figure in ThomsonNOW.
DinoflagellatesDinoflagellates
• Mostly unicellular, biflagellate, Mostly unicellular, biflagellate, photosynthetic photosynthetic alveolatesalveolates• major producers in marine ecosystemsmajor producers in marine ecosystems
• AlveoliAlveoli• flattened vesicles under plasma membraneflattened vesicles under plasma membrane• contain cellulose plates with silicates contain cellulose plates with silicates
• Some produce toxic blooms Some produce toxic blooms (red tides)(red tides)
DinoflagellatesDinoflagellates
ApicomplexansApicomplexans
• ParasitesParasites• produce produce sporozoitessporozoites• are nonmotileare nonmotile
• Apical complex of microtubulesApical complex of microtubules• attaches apicomplexan to host cell attaches apicomplexan to host cell
• PlasmodiumPlasmodium• causes malariacauses malaria
PlasmodiumPlasmodium
Fig. 25-10, p. 541
Infected female Anopheles mosquito bites uninfected human and transmits Plasmodium sporozoites to human blood. Anopheles
mosquito
Liver cell LiverSporozoites
(n)Meiosis
Sporozoites enter liver cells and divide to produce merozoites. Merozoites released from liver cells infect red blood cells.
Merozoites released
Zygote embeds in mosquito’s stomach lining and produces sporozoites (spores), which are released and migrate to salivary glands.
DIPLOID (2n) HAPLOID
(n)Red blood cells
Anopheles mosquito
In blood cells, merozoites divide to form more merozoites, which infect more red blood cells. Some merozoites form gametocytes.
Zygote (2n)
Fertilization Gametes
Gametocytes
In mosquito’s digestive tract, gametocytes develop into gametes, and fertilization occurs.
Uninfected female Anopheles mosquito bites infected person and obtains Plasmodium gametocytes.
1
2
3
45
6
Insert “Apicomplexan life Insert “Apicomplexan life cycle”cycle”
malaria_v2.swfmalaria_v2.swf
Watch the life cycle of the Watch the life cycle of the malaria parasite by clicking on malaria parasite by clicking on
the figure in ThomsonNOW.the figure in ThomsonNOW.
Learning Objective 7Learning Objective 7
• Describe and compare these Describe and compare these heterokontsheterokonts::• water moldswater molds• diatomsdiatoms• golden algaegolden algae• brown algaebrown algae
Water MoldsWater Molds
• HeterokontsHeterokonts• have two different kinds of flagellahave two different kinds of flagella
• Water moldsWater molds • have coenocytic have coenocytic myceliummycelium• reproduce asexually (biflagellate reproduce asexually (biflagellate zoosporeszoospores))• reproduce sexually (reproduce sexually (oosporesoospores))
• Phytophthora Phytophthora • causes late blight of potato, sudden oak deathcauses late blight of potato, sudden oak death
A Water MoldA Water Mold
Fig. 25-11a, p. 542
Fig. 25-11b, p. 542
Oospheres within oogonium2Meiosis results in haploid sperm nuclei within antheridia and haploid oospheres (eggs) within oogonia.
Sperm nuclei move into oospheres.
3
Antheridium (male reproductive structure)
Meiosis Fertilization
Haploid sperm nuclei
1 Saprolegnia reproduces sexually by antheridia and oogonia.
HAPLOID (n) GENERATION
Oospores
DIPLOID (2n) GENERATION
4 After fertilization, oospores develop from fertilized oospheres. Each oospore may develop into new mycelium.
Oogonium (female reproductive structure)
SEXUAL REPRODUCTION
Germination of oospore
Germination of the zoospore
MyceliumZoosporangium
Encysted secondary zoospore
ASEXUAL REPRODUCTION
(by mitosis)Zoospores
Secondary zoospore (bean-shaped)
5 Saprolegnia reproduces asexually by forming zoospores within zoosporangium.Encysted
primary zoospore
Primary zoospore (pear-shaped)
DiatomsDiatoms
• Mostly unicellular heterokontsMostly unicellular heterokonts• with shells containing silicawith shells containing silica• major producers in aquatic ecosystemsmajor producers in aquatic ecosystems
• Some are part of floating Some are part of floating planktonplankton
• Some live on rocks and sedimentsSome live on rocks and sediments• move by glidingmove by gliding
DiatomsDiatoms
Golden AlgaeGolden Algae
• Mostly unicellular, biflagellate freshwater Mostly unicellular, biflagellate freshwater and marine heterokontsand marine heterokonts• major component of tiny major component of tiny nanoplanktonnanoplankton
• CoccolithophoridsCoccolithophorids• golden algae covered by tiny, overlapping golden algae covered by tiny, overlapping
scales of calcium carbonatescales of calcium carbonate
Golden AlgaeGolden Algae
Brown AlgaeBrown Algae
• Multicellular heterokontsMulticellular heterokonts• important in cooler ocean waters important in cooler ocean waters
• Kelps (largest brown algae)Kelps (largest brown algae)• leaflike leaflike bladesblades• stemlike stemlike stipesstipes• anchoring anchoring holdfastsholdfasts• gas-filled bladders for buoyancygas-filled bladders for buoyancy
Brown AlgaeBrown Algae
Fig. 25-14a, p. 544
Blade
Stipe
Holdfast
Laminaria is widely distributed on rocky coastlines of temperate and polar seas. It grows to 2 m (6.5 ft.)
Learning Objective 8Learning Objective 8
• Describe Describe foraminiferansforaminiferans and and actinopodsactinopods
• Why do many biologists classify them in Why do many biologists classify them in the monophyletic group the monophyletic group cercozoacercozoa??
CercozoaCercozoa
• Amoeboid cellsAmoeboid cells
• Often have hard outer shells (Often have hard outer shells (teststests))• through which cytoplasmic projections extendthrough which cytoplasmic projections extend
ForaminiferansForaminiferans
• Secrete many-chambered testsSecrete many-chambered tests
• Pores through which cytoplasmic Pores through which cytoplasmic projections extendprojections extend• to move and obtain foodto move and obtain food
ForaminiferansForaminiferans
ActinopodsActinopods
• Mostly marine planktonMostly marine plankton
• Obtain food with Obtain food with axopodsaxopods• slender cytoplasmic projections that extend slender cytoplasmic projections that extend
through pores in shells through pores in shells
• RadiolariansRadiolarians• actinopods with glassy shellsactinopods with glassy shells
ActinopodsActinopods
Learning Objective 9Learning Objective 9
• Support the hypothesis that Support the hypothesis that red algaered algae and and green algaegreen algae should be included in a should be included in a monophyletic group with monophyletic group with land plantsland plants
PlantsPlants
• Monophyletic group includingMonophyletic group including• red algaered algae• green algaegreen algae• land plants land plants
• Based onBased on• molecular datamolecular data• presence of chloroplasts bounded by outer presence of chloroplasts bounded by outer
and inner membranesand inner membranes
Red AlgaeRed Algae
• Mostly multicellular seaweedsMostly multicellular seaweeds• important in warm tropical ocean watersimportant in warm tropical ocean waters
• Some red algae incorporate calcium Some red algae incorporate calcium carbonate in cell wallscarbonate in cell walls• important in reef buildingimportant in reef building
Red AlgaeRed Algae
Insert “Red alga life Insert “Red alga life cycle”cycle”
porphyra.swfporphyra.swf
Green AlgaeGreen Algae
• Wide diversity in size, structural Wide diversity in size, structural complexity, and reproduction complexity, and reproduction
• Botanists hypothesize that ancestral green Botanists hypothesize that ancestral green algae gave rise to land plantsalgae gave rise to land plants
Green AlgaeGreen Algae
ChlamydomonasChlamydomonas
Fig. 25-17, p. 547
5 Both mating types reproduce asexually by mitosis; only (-) strain is shown.–
–
– Zoospores
ASEXUAL REPRODUCTION
(by mitosis)
–
–
4 Four haploid cells emerge, two (+) and two (-).
1 Gametes are produced by mitosis.
+
–– – SEXUAL
REPRODUCTION
+HAPLOID (n)
GENERATION–
+–from a different strain
DIPLOID (2n) GENERATION 2 (+) and (-)
gametes fuse, forming a diploid zygote.
+Meiosis Fertilization
3Meiosis occurs.
Zygote (2n)
Insert “Green alga life Insert “Green alga life cycle”cycle”
chlamydomonas_v2.swfchlamydomonas_v2.swf
UlvaUlva
Fig. 25-18, p. 548
4Each zoospore develops into multicellular male or female individual.
Mature haploid alga
Zoospores Gamete
1 Male and female algae produce biflagellate gametes by mitosis.
HAPLOID (n) GENERATION
Zoospores
Anisogamous gametes
DIPLOID (2n) GENERATION
3 Special cells in diploid alga undergo meiosis to form haploid zoospores.
Meiosis Fertilization
2 Gametes fuse, forming zygote, which attaches to substrate and develops into multicellular individual.
Motile zygote
Mature diploid alga
SpirogyraSpirogyra
Fig. 25-19a, p. 548
Fig. 25-19b, p. 548
Fig. 25-19c, p. 548
Fig. 25-19d, p. 548
KEY CONCEPTSKEY CONCEPTS
• Animals, fungi, and plants evolved from Animals, fungi, and plants evolved from protist ancestorsprotist ancestors
Learning Objective 10Learning Objective 10
• Describe and compare these Describe and compare these amoebozoaamoebozoa::• amoebasamoebas• plasmodial slime moldsplasmodial slime molds• cellular slime moldscellular slime molds
AmoebasAmoebas
• Use cytoplasmic extensions Use cytoplasmic extensions (pseudopodia)(pseudopodia)• to moveto move and obtain food by and obtain food by phagocytosisphagocytosis
• Entamoeba histolytica Entamoeba histolytica • parasitic amoebaparasitic amoeba• causes amoebic dysenterycauses amoebic dysentery
AmoebaAmoeba
Fig. 25-22, p. 549
Green alga
Pseudopodia
100 µm
Plasmodial Slime MoldsPlasmodial Slime Molds
• Feeding stage is multinucleate Feeding stage is multinucleate plasmodiumplasmodium
• Reproduction is by haploid spores produced Reproduction is by haploid spores produced within within sporangiasporangia
PhysarumPhysarum
Fig. 25-23a, p. 550
Fig. 25-23b, p. 550
Cellular Slime MoldsCellular Slime Molds
• Feed as individual amoeboid cells Feed as individual amoeboid cells
• Reproduce by aggregating into a Reproduce by aggregating into a pseudoplasmodiumpseudoplasmodium (slug) (slug)• then form asexual sporesthen form asexual spores
DictyosteliumDictyostelium
Insert “Cellular slime Insert “Cellular slime mold life cycle”mold life cycle”
slime_mold.swfslime_mold.swf
KEY CONCEPTSKEY CONCEPTS
• Biologists are making progress in Biologists are making progress in understanding the evolutionary understanding the evolutionary relationships among various protist taxarelationships among various protist taxa
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