Chapter 28 Protista
• Overview: A World in a Drop of Water
• Even a low-power microscope– Can reveal an astonishing menagerie of
organisms in a drop of pond water
Figure 28.150 m
Movie
• Protista- single or colonies of eukaryotic cells (Ameoba, Paramecium)
Animal-Like Protists
8-14
Fig. 8.22
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Cladogram of Protozoa Relationships
Animal-Like Protists: The Protozoa
and Colonial Eukaryotes
Unicellular
Figure 8.3
These amazing organismsBelong to the diverse kingdoms of mostly single-celled eukaryotes informally known as protists
• 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
• Protist habitats are also diverse in habitat• And including freshwater and marine species
Figure 28.2a–d
100 m
100 m
4 cm
500 m
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)
• A sample of protist diversity
Endosymbiosis in Eukaryotic Evolution
Cyanobacterium
Heterotrophiceukaryote
Primaryendosymbiosis
Red algae
Green algae
Secondaryendosymbiosis
Secondaryendosymbiosis
Plastid
Dinoflagellates
Apicomplexans
Ciliates
Stramenopiles
Euglenids
Chlorarachniophytes
Plastid
Alv
eola
tes
Figure 28.3
• Diversity of plastids produced by secondary endosymbiosis
• Concept 28.2: Diplomonads and parabasalids have modified mitochondria
• A tentative phylogeny of eukaryotes– Divides eukaryotes into many clades
Figure 28.4
Dip
lom
ona
ds
Par
aba
salid
s
Kin
etop
last
ids
Eug
leni
ds
Din
ofla
gel
late
s
Api
com
ple
xan
s
Cili
ate
s
Oo
myc
ete
s
Dia
tom
s
Go
lden
alg
ae
Bro
wn
alg
ae
Ch
lora
rach
nio
phy
tes
Fo
ram
inife
ran
s
Ra
dio
laria
ns
Gym
nam
oeba
s
Ent
amoe
bas
Pla
smo
dia
l slim
e m
olds
Ce
llula
r sl
ime
mo
lds
Fu
ngi
Ch
oan
ofla
ge
llate
s
Met
azo
ans
Re
d al
gae
Ch
loro
phyt
es
Ch
aro
phy
cea
ns
Pla
nts
Ancestral eukaryote
Ch
loro
ph
yta
Pla
nta
e
Rh
od
op
hyt
a
An
ima
lia
Fu
ng
i
(Opisthokonta) (Viridiplantae)Dip
lom
on
ad
ida
Par
aba
sal
a
Eu
gle
no
zoa
Alveolata Stramenopila Ce
rco
zoa
Ra
dio
lari
a
Amoebozoa
• Diplomonads and parabasalids– 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
Figure 28.5a5 µm
(a) Giardia intestinalis, a diplomonad (colorized SEM)
Parabasalids• Parabasalids include trichomonads
– Which move by means of flagella and an undulating part of the plasma membrane
Figure 28.5b (b) Trichomonas vaginalis, a parabasalid (colorized SEM)
Flagella
Undulating membrane 5 µm
• Concept 28.3: Euglenozoans have flagella with a unique internal structure
• Euglenozoa is 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
Flagella0.2 µm
Crystalline rod
Ring of microtubulesFigure 28.6
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
• The parasitic kinetoplastid Trypanosoma– Causes sleeping sickness in humans
Figure 28.79 m
8-6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 8.9
Life Cycle of Trypanosoma Brucei
Figure 8.8 (b)
Phylum Sarcomastigophora
• Chars: Flagella, pseudopodia, or both; single type of nucleus; no spores formed.
• Subphylum Masigophora– Chars: One or more Flagella– Autotrophic (cl. Phytomastigophora)– Heterotrophic (cl. Zoomastigophora) or both;– Reproduction usually by fission
8-4
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Fig. 8.7
Structure of Euglena
Subphylum Mastigophora
(cl. Phytomastigophora)
Euglenids• Euglenids
– Have one or two flagella that emerge from a pocket at one end of the cell
– Store the glucose polymer paramylon
Figure 28.8
Long flagellum
Short flagellum
Nucleus
Plasma membrane
Paramylon granule
Chloroplast
Contractile vacuole
Light detector: swelling near thebase of the long flagellum; detectslight that is not blocked by theeyespot; as a result, Euglena movestoward light of appropriateintensity, an important adaptationthat enhances photosynthesis
Eyespot: pigmentedorganelle that functions
as a light shield, allowinglight from only a certain
direction to strike thelight detector
Pellicle: protein bands beneaththe plasma membrane that
provide strength and flexibility(Euglena lacks a cell wall)
Euglena (LM)5 µm
• Concept 28.4: Alveolates have sacs beneath the plasma membrane
• Members of the clade Alveolata– Have membrane-bounded sacs (alveoli) just
under the plasma membrane
Figure 28.9
FlagellumAlveoli0.2 µm
Dinoflagellates
• Dinoflagellates– Are a diverse group of aquatic
photoautotrophs and heterotrophs– 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
• Two flagella– Make them spin as they move through the
water
Figure 28.10 3 µ
m
Flagella
Figure 8.6
Phylum Dinozoa: Dinoflagellates
• Rapid growth of some dinoflagellates– Is responsible for causing “red tides,” which
can be toxic to humans
Apicomplexans• Apicomplexans
– Are parasites of animals and some cause serious human diseases
– Are so named because one end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues
– Have a nonphotosynthetic plastid, the apicoplast
Phylum Apicomplexa
• Chars: All parasites
• Apical complex used for penetrating host cells
• Lack cilia and flagella, except in certain reproductive stages
• Coccidians or apicomplexans are named based upon the presence of apical complex
Most important Coccidians are members of the class
Sporozoea
• Chars: intracellular parasites of animals• Form spores or oocysts following sexual
reproduction• Complex life cycle that involve both
vertebrate and invertebrate hosts
• Example- Plasmodium the sporozoan that causes malaria.
Figure 28.11
Inside mosquito Inside human
Sporozoites(n)
Oocyst
MEIOSIS
Liver
Liver cell
Merozoite(n)
Red bloodcells
Gametocytes(n)
FERTILIZATION
Gametes
Zygote(2n)
Key
Haploid (n)Diploid (2n)
Merozoite
Red blood cell
Apex
0.5 µm
• Most apicomplexans have intricate life cycles – With both sexual and asexual stages that often
require two or more different host species for completion
An infected Anopheles mosquito bites a person, injecting Plasmodium sporozoites in its saliva.
1 The sporozoites enter the person’s liver cells. After several days, the sporozoites undergo multiple divisions and become merozoites, which use their apical complex to penetrate red blood cells (see TEM below).
2
The merozoites divide asexually inside the red blood cells. At intervals of 48 or 72 hours (depending on the species), large numbers of merozoites break out of the blood cells, causing periodic chills and fever. Some of the merozoites infect new red blood cells.
3
Some merozoites form gametocytes.4
Another Anopheles mosquitobites the infected person and picksup Plasmodium gametocytes alongwith blood.
5 Gametes form from gametocytes.Fertilization occurs in the mosquito’sdigestive tract, and a zygote forms.The zygote is the only diploid stagein the life cycle.
6
An oocyst developsfrom the zygote in the wall of the mosquito’s gut. Theoocyst releases thousands
of sporozoites, whichmigrate to the mosquito’s
salivary gland.
7
8-10
Fig. 8.15
Life Cycle of Plasmodium
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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
Phylum Ciliophora
• Chars: Cilia, macronuclei, and micronuclei usually present
• Ciliates are the largest most complex and diverse group of the protozoans
• Nearly occupy all aquatic habitats• Some are symbiotic• Reproduction can be asexual through
fission or sexual through conjugation
Example of a Ciliophora: Paramecium
• Common freshwater ciliate
• Observe live sample using methylcellulose solution
• Other Ciliophora: Colpidium, Vorticella and Stentor
Figure 28.12
50 µmThousands of cilia cover
the surface of Paramecium.
The undigested contents of food vacuoles are released when the vacuoles fuse with a specialized region of the plasma membrane that functions as an anal pore.
Paramecium, like other freshwater protists, constantly takes in water
by osmosis from the hypotonic environment. Bladderlike contractile vacuoles accumulate
excess water from radial canals and periodically expel it through the plasma membrane.
Food vacuoles combine with lysosomes. As the food is digested, the vacuoles follow a looping path through the cell.
Paramecium feeds mainly on bacteria. Rows of cilia along a funnel-shaped oral groove move food into the cell mouth, where the food is engulfed into food vacuoles by phagocytosis.
Oral groove
Cell mouth
Micronucleus
Macronucleus
FEEDING, WASTE REMOVAL, AND WATER BALANCE
• Exploring structure and function in a ciliate
Contractile Vacuole
CONJUGATION AND REPRODUCTION
8 7
2
MICRONUCLEARFUSION
Diploidmicronucleus
Diploidmicronucleus
Haploidmicronucleus
MEIOSIS
Compatiblemates
Key
Conjugation
Reproduction
Macronucleus
Two cells of compatiblemating strains align sideby side and partially fuse.
1 Meiosis of micronuclei produces four haploidmicronuclei in each cell.
23 Three micronuclei in each cell
disintegrate. The remaining micro-nucleus in each cell divides by mitosis.
The cells swap one micronucleus.
4
The cellsseparate.
5
Micronuclei fuse,forming a diploid micronucleus.
6Three rounds of mitosis without cytokinesis produce eight micronuclei.
7 The original macro-nucleus disintegrates. Four micronuclei become macronuclei, while the other four remain micronuclei.
8Two rounds of cytokinesis partition one macronucleus and one micronucleus into each of four daughter cells.
9
Asexual Reproduction in Protozoa - ciliophora
Binary Fission of Ciliated Stentor
Stentor ciliophora
• Concept 28.5: Stramenopiles have “hairy” and smooth flagella
• The clade Stramenopila– Includes several groups of heterotrophs as
well as certain groups of algae
• Most stramenopiles– Have a “hairy” flagellum paired with a
“smooth” flagellum
Smoothflagellum
Hairyflagellum
5 µmFigure 28.13
• The life cycle of a water mold
Figure 28.14
Cyst
Zoospore(2n)
ASEXUALREPRODUCTION
Zoosporangium(2n)
Germ tube
Zygotegermination
FERTILIZATIONSEXUALREPRODUCTION
Zygotes(oospores)(2n)
MEIOSIS
OogoniumEgg nucleus(n) Antheridial
hypha withsperm nuclei(n)
Key
Haploid (n)Diploid (2n)
Encysted zoosporesland on a substrate andgerminate, growing intoa tufted body of hyphae.
1 Several days later,the hyphae begin toform sexual structures.
2 Meiosis produceseggs within oogonia(singular, oogonium).
3 On separate branches of thesame or different individuals, meiosisproduces several haploid sperm nucleicontained within antheridial hyphae.
4
Antheridial hyphae grow likehooks around the oogonium anddeposit their nuclei throughfertilization tubes that lead to theeggs. Following fertilization, thezygotes (oospores) may developresistant walls but are alsoprotected within the wall of theoogonium.
5
A dormant periodfollows, during which theoogonium wall usuallydisintegrates.
6
The zygotes germinateand form hyphae, and thecycle is completed.
7
The endsof hyphae
form tubularzoosporangia.
8
Each zoospor-angium produces
about 30biflagellated
zoosporesasexually.
9
Diatoms• Diatoms are unicellular algae
– With a unique two-part, glass-like wall of hydrated silica
Figure 28.15 3 µ
m
• Diatoms are a major component of phytoplankton– And are highly diverse
Figure 28.16 50 µm
• Most golden algae are unicellular– But some are colonial
Figure 28.17
25 µm
• Brown algae– Include many of the species commonly called
seaweeds
• Seaweeds– Have the most complex multicellular anatomy of
all algae
Figure 28.18
Blade
Stipe
Holdfast
• Kelps, or giant seaweeds– Live in deep parts of the ocean
Figure 28.19
• Concept 28.6: Cercozoans and radiolarians have threadlike pseudopodia
• A newly recognized clade, Cercozoa– Contains a diversity of species that are among
the organisms referred to as amoebas
• Amoebas were formerly defined as protists– That move and feed by means of pseudopodia
• Cercozoans are distinguished from most other amoebas– By their threadlike pseudopodia
Foraminiferans (Forams)
• Foraminiferans, or forams– Are named for their porous, generally
multichambered shells, called tests20 µm
• Pseudopodia extend through the pores in the test
• Foram tests in marine sediments– Form an extensive fossil record
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
Figure 28.23200 µm
Axopodia
• Concept 28.7: Amoebozoans have lobe-shaped pseudopodia
• Amoebozoans– Are amoeba that have lobe-shaped, rather
than threadlike, pseudopodia– Include gymnamoebas, entamoebas, and
slime molds
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
Figure 28.24
Pseudopodia
40 µm
Entamoebas
• Entamoebas– Are parasites of vertebrates and some
invertebrates
• Entamoeba histolytica– Causes amebic dysentery in humans
8-7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 8.10
Variations in Pseudopodia
8-8
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Fig. 8.11b
Subphylum Sarcodina: Superclass Rhizopoda, Class Lobosea
Other Sarcodina-“Not naked” sarcodines
• Arcella, Difflugia, and Actinospaerium and marine radiolarians and foraminifera form test.
• Test can be formed from sand grains, calcium carbonate and silica
8-9
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Fig. 8.12
Freshwater Amoeba (Difflugia Oblongata)
• Concept 28.8: Red algae and green algae are the closest relatives of land plants
• Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont– And the photosynthetic descendants of this
ancient protist evolved into red algae and green algae
Green Algae
• Green algae– Are named for their grass-green chloroplasts– Are divided into two main groups:
chlorophytes and charophyceans– Are closely related to land plants
• Most chlorophytes– Live in fresh water, although many are marine
• Other chlorophytes– Live in damp soil, as symbionts in lichens, or
in snow
Figure 28.29
• Chlorophytes include– Unicellular, colonial, and multicellular forms
Volvox, a colonial freshwater chlorophyte. The colony is a hollowball whose wall is composed of hundreds or thousands of biflagellated cells (see inset LM) embedded in a gelatinous matrix. The cells are usually connected by strands of cytoplasm;if isolated, these cells cannot reproduce. The large colonies seen here will eventually release the small “daughter” colonies within them (LM).
(a)
Caulerpa, an inter-tidal chlorophyte.The branched fila-ments lack cross-walls and thus are multi-nucleate. In effect,the thallus is onehuge “supercell.”
(b)
Ulva, or sea lettuce. This edible seaweed has a multicellular thallus differentiated into leaflike blades and a rootlike holdfast that anchors the alga against turbulent waves and tides.
(c)
20 µm50 µm
Figure 28.30a–c
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 8.8
Volvox, A Colonial Flagellate
Figure 28.31
Flagella
Cell wall
Nucleus
Regionsof singlechloroplast
Zoospores
ASEXUALREPRODUCTION
Mature cell(n)
SYNGAMY
SEXUALREPRODUCTION Zygote
(2n)
MEIOSIS
1 µm
Key
Haploid (n)
Diploid (2n)
++
+
+
• Most chlorophytes have complex life cycles– With both sexual and asexual reproductive
stages In Chlamydomonas,mature cells are haploid and contain a single cup-shaped chloroplast (see TEM at left).
1 In response to ashortage of nutrients, dryingof the pond, or some otherstress, cells develop into gametes.
2
Gametes of opposite mating types (designated + and –) pair off and cling together. Fusion of the gametes (syngamy) forms a diploid zygote.
3
The zygote secretes a durable coat that protects the cell against harsh conditions.
4
After a dormant period, meiosis produces four haploid individuals (two of each mating type) that emerge fromthe coat and develop into mature cells.
5
When a mature cell repro-duces asexually, it resorbs its flagella and then undergoes two rounds of mitosis, forming four cells (more in some species).
6
These daughter cells develop flagella and cell walls and then emerge as swimming zoospores from the wall of the parent cell that had enclosed them. The zoospores grow into mature haploid cells, completing the asexual life cycle.
7