Protista
“First Animal”
• 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
M
o
v
i
e
50 m
• Protista- single or colonies of
eukaryotic cells (Ameoba,
Paramecium)
Animal-Like Protists
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Cladogram of Protozoa Relationships
Fig. 8.22
8-14
Animal-Like Protists: The Protozoa
Unicellular
and Colonial Eukaryotes
Figure 8.3
These amazing organisms
Belong to the diverse
kingdoms of mostly singlecelled 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
(a) The freshwater ciliate Stentor,
a unicellular protozoan (LM)
Stentor
100 m
100 m
4 cm
(c)
(b) Ceratium tripos, a unicellular marine dinoflagellate (LM)
Delesseria sanguinea, a multicellular marine red alga
500 m
Figure 28.2a–d
(d)
Spirogyra, a filamentous freshwater green alga (inset LM)
• A sample of protist diversity
• Diversity of plastids produced by
secondary endosymbiosis
Plastid
Alveolates
Dinoflagellates
Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Ciliates
Red algae
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Green algae
Figure 28.3
Chlorarachniophytes
Figure 28.4
Diplomonadida
Apicomplexans
Ancestral eukaryote
Plants
Charophyceans
(Opisthokonta)
Chlorophytes
Red algae
Metazoans
Choanoflagellates
Amoebozoa
Fungi
Cellular slime molds
Plasmodial slime molds
Entamoebas
Gymnamoebas
Plantae
Chlorophyta
Rhodophyta
Animalia
Fungi
Radiolarians Radiolaria
Cercozoa
Stramenopila
Foraminiferans
Chlorarachniophytes
Brown algae
Golden algae
Diatoms
Oomycetes
Ciliates
Euglenozoa
Alveolata
Dinoflagellates
Euglenids
Kinetoplastids
Parabasalids Parabasala
Diplomonads
• Diplomonads and parabasalids have
modified mitochondria
• A tentative phylogeny of eukaryotes
– Divides eukaryotes into many clades
(Viridiplantae)
• 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
Parabasalids
• Parabasalids include trichomonads
– Which move by means of flagella and an
undulating part of the plasma membrane
Flagella
Undulating membrane
5 µm
Figure 28.5b (b) Trichomonas vaginalis, a parabasalid (colorized SEM)
• 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
Flagella
0.2 µm
Crystalline rod
Figure 28.6
Ring of microtubules
Subphylum Kinetoplasta
• 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
Class Trypanosomatidea
• The parasitic kinetoplastid Trypanosoma
– Causes sleeping sickness in humans
Figure 28.7
9 m
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Life Cycle of Trypanosoma Brucei
Fig. 8.9
8-6
Figure 8.8 (b)
Super Phylum
Sarcomastigophora
• Chars: Flagella, pseudopodia, or both;
single type of nucleus; no spores formed.
• Subphylum Mastigophora
– Chars: One or more Flagella
– Autotrophic (cl. Phytomastigophora)
– Heterotrophic (cl. Zoomastigophora) or both;
– Reproduction usually by fission
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Structure of Euglena
Fig. 8.7
Also classified as
Phylum Euglenozoa
Subphylum Euglenida
Cl. Euglenoidea
Subphylum Mastigophora
(cl. Phytomastigophora)
8-4
Subphylum Euglenida
• Euglenids
– Have one or two flagella that emerge from a
pocket at one end of the cell
– Store the glucose polymer paramylon
Long flagellum
Eyespot: pigmented
organelle that functions
as a light shield, allowing
light from only a certain
direction to strike the
light detector
Light detector: swelling near the
base of the long flagellum; detects
light that is not blocked by the
eyespot; as a result, Euglena moves
toward light of appropriate
intensity, an important adaptation
that enhances photosynthesis
Short flagellum
Euglena (LM)
Nucleus
Contractile vacuole
5 µm
Plasma membrane
Figure 28.8
Pellicle: protein bands beneath
the plasma membrane that
provide strength and flexibility
(Euglena lacks a cell wall)
Chloroplast
Paramylon granule
Figure 8.6
Phylum Dinozoa: Dinoflagellates
Phylum Dinozoa
• 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
Flagella
Figure 28.10
• Rapid growth of some dinoflagellates
– Is responsible for causing “red tides,” which
can be toxic to humans
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
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
Ampicomplexan is an Alveolate
• Alveolates have sacs beneath the plasma
membrane- plasmodium, also seen in
other phylums i.e. paramecium and stentor
• Members of the clade Alveolata
– Have membrane-bounded sacs (alveoli) just
Alveoli
0.2 µm
under the plasma
membrane
Flagellum
Figure 28.9
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- Cl. Coccidea Plasmodium the
sporozoan that causes malaria.
• Most apicomplexans have intricate life cycles
– With both sexual and asexual stages that often
require two or more different host species for
completion
2 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).
1 An infected Anopheles
mosquito bites a person,
injecting Plasmodium
sporozoites in its saliva.
Inside mosquito
Inside human
Sporozoites
(n)
7 An oocyst develops
from the zygote in the wall
of the mosquito’s gut. The
oocyst releases thousands
of sporozoites, which
migrate to the mosquito’s
salivary gland.
Merozoite
Liver
Liver cell
Apex
Oocyst
MEIOSIS
Zygote
(2n)
Red blood
cell
Merozoite
(n)
Red blood
cells
FERTILIZATION
Gametes
Key
3 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.
Gametocytes
(n)
Haploid (n)
Diploid (2n)
Figure 28.11
0.5 µm
4 Some merozoites
form gametocytes.
6 Gametes form from gametocytes.
Fertilization occurs in the mosquito’s
digestive tract, and a zygote forms.
The zygote is the only diploid stage
in the life cycle.
5 Another Anopheles mosquito
bites the infected person and picks
up Plasmodium gametocytes along
with blood.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Life Cycle of Plasmodium
Fig. 8.15
8-10
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
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
Example of a Ciliophora:
Paramecium
• Common freshwater ciliate
• Observe live sample using methylcellulose
solution
• Other Ciliophora: Colpidium, Vorticella and
Stentor
• Exploring structure and function in a ciliate
FEEDING, WASTE REMOVAL, AND WATER BALANCE
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.
Contractile Vacuole
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
50 µm
Thousands of cilia cover
the surface of Paramecium.
Micronucleus
Food vacuoles combine with
lysosomes. As the food is digested,
the vacuoles follow a looping path
through the cell.
Macronucleus
Figure 28.12
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.
CONJUGATION AND REPRODUCTION
2
1 Two cells of compatible
mating strains align side
by side and partially fuse.
2 Meiosis of micronuclei
produces four haploid
MEIOSIS
micronuclei in each cell.
3 Three micronuclei in each cell
disintegrate. The remaining micronucleus in each cell divides by mitosis.
Macronucleus
Compatible
mates
4 The cells swap
one micronucleus.
Haploid
micronucleus
Diploid
micronucleus
Diploid
micronucleus
MICRONUCLEAR
FUSION
5
9 Two rounds of cytokinesis
partition one macronucleus
and one micronucleus
into each of four daughter cells.
8
7
8 The original macronucleus disintegrates.
Four micronuclei
become macronuclei,
while the other four
remain micronuclei.
7 Three rounds of
mitosis without
cytokinesis
produce eight
micronuclei.
6 Micronuclei fuse,
forming a diploid
micronucleus.
The cells
separate.
Key
Conjugation
Reproduction
Asexual Reproduction in Protozoa - ciliophora
Binary Fission of Ciliated Stentor
Stentor ciliophora
• 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
Hairy
flagellum
Smooth
flagellum
Figure 28.13
5 µm
Diatoms
• Diatoms are unicellular algae
– With a unique two-part, glass-like wall of
hydrated silica
Figure 28.15
• 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
25 µm
Figure 28.17
• Brown algae
– Include many of the species commonly called
seaweeds
• Seaweeds
– Have the most complex multicellular anatomy of
all algae
Blade
Stipe
Figure 28.18
Holdfast
Phylum Granuloreticulosa
• Cl. Foraminiferans, or forams
– Are named for their porous, generally
multichambered shells, called tests
20 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
Axopodia
Figure 28.23
200 µm
• 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
Pseudopodia
40 µm
Figure 28.24
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Variations in Pseudopodia
Fig. 8.10
8-7
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Subphylum Sarcodina: Superclass Rhizopoda, Class Lobosea
Fig. 8.11b
8-8
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
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Freshwater Amoeba (Difflugia Oblongata)
Fig. 8.12
8-9
Chlorophyta
• Green algae
– Are named for their grass-green chloroplasts
– Are divided into two main groups:
chlorophytes and charophyceans
– Are closely related to land plants
• 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
Endosymbiosis in
Eukaryotic Evolution
• Chlorophytes include
– Unicellular, colonial, and multicellular forms
20 µm
50 µm
(a)
(b)
Volvox, a colonial freshwater chlorophyte. The colony is a hollow
ball 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).
Caulerpa, an intertidal chlorophyte.
The branched filaments lack cross-walls
and thus are multinucleate. In effect,
the thallus is one
huge “supercell.”
Figure 28.30a–c
(c) 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.
Volvox, A Colonial Flagellate
Fig. 8.8
Volvox
Volvox
8-5
• Most chlorophytes have complex life
cycles
– With both sexual and asexual reproductive
stages
7 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.
Flagella
1 In Chlamydomonas,
mature cells are haploid and
contain a single cup-shaped
chloroplast (see TEM at left).
2 In response to a
shortage of nutrients, drying
of the pond, or some other
stress, cells develop into gametes.
3 Gametes of opposite
mating types (designated
+ and –) pair off and
cling together. Fusion of
the gametes (syngamy)
forms a diploid zygote.

1 µm
Cell wall
+
Nucleus

+
Zoospores
Regions
of single
chloroplast
ASEXUAL
REPRODUCTION
Mature cell
(n)
SEXUAL
REPRODUCTION
+
Key
Haploid (n)
Diploid (2n)
Figure 28.31
+
6 When a mature cell reproduces asexually, it resorbs its
flagella and then undergoes two
rounds of mitosis, forming four
cells (more in some species).
SYNGAMY
Zygote
(2n)

MEIOSIS
4 The zygote secretes
a durable coat that
protects the cell against
harsh conditions.
5 After a dormant period, meiosis
produces four haploid individuals (two
of each mating type) that emerge from
the coat and develop into mature cells.