Protists

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


• 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


• 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)


• 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


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


Chloroplast DNA

Chloroplast with two membranes

Eukaryotic cell with mitochondria and chloroplasts (red alga)

(a) Primary endosymbiosis Cyanobacterium

(ancestor of chloroplast)

Bacterial DNA


Mitochondrion

Nucleus


• 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

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Ancestral eukaryote

Eukaryote CladesEukaryote Clades

Fig. 25-4, p. 535

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Ancestral eukaryote


• Protists are descendants of early Protists are descendants of early eukaryoteseukaryotes


• 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


• 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.


• 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.)


• 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


• 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


• Animals, fungi, and plants evolved from Animals, fungi, and plants evolved from protist ancestorsprotist ancestors


• 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


• 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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Protists