Kingdom Protista
The Link Between Bacteria
and the Multicellular World
• There are
plant-like
protists that
photosynthesize
–
–
–
–
Dinoflagellates
Euglena
Diatoms
Algae
The Link Between Bacteria
and the Multicellular World
• Some are
carnivorous
protists that are
hunters
– Amoebas
– Ciliates
The Link Between Bacteria
and the Multicellular World
• Finally, some
are like fungus,
because they
absorb nutrients
from the
surroundings
and produce
spores.
– Slime molds.
Protist: Characteristics
• All are Eukaryotic
• Some motile, some not
• Some single-celled, some
multicellular.
• Variety of Ways to Get Energy
– Some are
• Carnivorous
• Photosynthetic
• Chemoautotrophic
• Detritivores
Characteristics
• Reproduction
– Primarily Asexual
• Budding
• Fragmentation
• Spores
– Sexual (less common but does happen)
• Many events happen in times of stress
• Male + Female gametes
• Sometimes, protists
Protista:
General
Characteristics
Classification
and Phylogeny
prokaryotic
ancestor
diplomonads Flagellated
parabasalids Protozoans
trypanosomes
euglenoids
radiolarians
foraminiferans
ciliates
Alveolates
dinoflagellates
apicomplexans
water molds
diatoms Stramenopiles
brown algae
Figure 22.2
Single-celled protists include (a)
amoebas, (b) euglenoids, and (c)
diatoms. Most red algae (d) and all
brown algae (e) are multicelled. (f) One
proposed eukaryotic family tree with
traditional protist groups indicated by tan
boxes. Notice that the protists are not
united as a single lineage.
Figure It Out: Are land plants more
closely related to the red algae or the
brown algae?
Answer: red algae
red algae
chlorophyte algae Green
charophyte algae Algae
land plants
amoebas Amoebozoans
slime molds
fungi
choanoflagellates
animals
Group: Flagellated
Protozoans
• Flagellated protozoans are singlecelled protists covered by a pellicle
(proteins that help cells retain shape)
• They swim in lakes, seas, and the
body fluids of animals
• They are typically heterotrophic and
reproduce asexually by binary
fission
Trypanosomes and
Other Kinetoplastids
• Kinetoplastids are flagellated
protozoans with a single large
mitochondrion
• Trypanosomes include human
pathogens that are transmitted by
insects
– African sleeping sickness (T. brucei) is
spread by tsetse flies
– Chagas disease (T. cruzi) is spread by
bloodsucking bugs
Human Disease
Trypanosoma
•African sleeping sickness
•Transmitted by tsetse fly
•Causes fever, mental
deterioration and coma
•No means of
locomotion- most
are parasitic and
don’t need it
•Sexual
reproduction
present
•Environmentparasitic-aquatic
Phylum
Zoomastigina
Human Disease
Giardia
•Causes giardiasis
•Sever diarrhea and
intestinal cramps
•Parasite in
contaminated water
•Thousands of cases
annually in U.S.
A SEM micrograph of the small intestine of
a gerbil infested with Giardia reveals a
mucosa surface almost entirely obscured by
attached trophozoites
•Not usually fatal,
but, you can
imagine,
uncomfortable.
The Euglenoids
• Euglenoids are flagellated protists
related to kinetoplastids that do not
infect humans
– Most prey on bacteria
– Some have chloroplasts that evolved from
green algae and can detect light with an
eyespot
– Most live in freshwater and have contractile
vacuoles that expel excess water
Foraminiferans &
Radiolarians
• Heterotrophic single cells with chalky
or glassy shells live in great numbers
in the world’s oceans; cytoplasm
extends through many pores.
• Most forams live on the seafloor;
others drift as part of the plankton.
Phylum Actinopoda
• Radiolarians
• Silica test
• Pseudopodia
used for food
getting
• Asexual
reproduction
• Mostly
marine
Phylum Foraminifera
Forams
•Locomotion and
food getting by
pseudopodia
•Calcium
carbonate test
•Environmentprimarily marine
Group: Alveolates/
Ciliates
• Ciliates are heterotrophic single
cells that move about with the help
of cilia
• Ciliates reproduce asexually by
binary fission or sexually by
conjugation.
Phylum Ciliophora
• Locomotion and
food getting by cilia
• Pellicle present
maintains shape
• Contractile vacuoles
remove excess
water
• Sexual reproduction
by conjugation
• Environmentaquatic
• Heterotrophic &
parasitic
Paramecium
•Unicellular
•Heterotrophic
•Cilia
•Requires oxygen to live
= aerobic environment
•Asexual & Sexual Reproduction
•Special Quality
2 nucleii
•Found in most aquatic
environments
Phylum Ciliophora
Stentor
•Largest
freshwater
protozoan
•Can regenerate
body parts
•Cilia covers
body
for movement &
feeding
Phylum Ciliophora
Didinium
This
organism is
aggressive
and has a
huge
appetite
Didinium feeding
Attaches to paramecium
Starts to ingest
Almost completely engulfed
Phylum Apicomplexa
•Protozoan that causes
malaria
•Plasmodium enters
bloodstream, travels to liver
cells, where they divide and
release new spores into the
bloodstream.
•Parasitic
•No locomotion
•Reproduce asexually
•Transmitted by bite of
infected mosquito
•Destroys red blood cells
Group: Stramenopiles
• “Red Algae”
• Brown algae are
multi-celled protists
that live in temperate
or cool seas; ranging
from microscopic
filaments to giant kelp
• Some brown algae are
used commercially
– Thickeners (algins),
food, fertilizer, herbal
supplements
(bladderwrack)
Diatoms
• Diatoms are singlecelled or colonial
protists that have a
two-part silica shell
– Shells accumulate on
the seafloor
(diatomaceous earth)
• Most are
photosynthetic, with a
brown accessory
pigment (fucoxanthin)
– Major components of
phytoplankton
Group: Red Algae
• Red algae are mostly multicelled marine algae that live
in clear, warm waters
• Red accessory pigments
(phycobilins) allow red algae
to live at greater depths
than other algae
• Red and green algae share a
common ancestor with
chloroplasts derived from
cyanobacteria
• Life cycles vary and are
often complex, with both
asexual and sexual phases;
there is no flagellated stage.
Group: Green Algae
• Most green algae are chlorophytes
– Chlorella: Single celled, grown as health food
– Chlamydomonas: Single celled, freshwater
alga
– Volvox: Colonial, freshwater alga
– Cladophora: Forms long filaments
– Ulva: “Sea lettuce”
– Codium fragilis: Branching marine alga
• Charophyte algae
include several lineages
that form a clade with land
plants
– Desmids: A single-celled,
freshwater group
– Spirogyra: Forms long
filaments
– Stoneworts (Chara):
Closely related to land
plants
Group: Amoebozoans
• Amoebozoans send out pseudopods,
move about, and capture food
– Most have no cell walls, shell, or
pellicles
• Amoebas live as single cells
– Example: Amoeba proteus, a freshwater
predator
• Slime molds are “social amoebas”
– Plasmodial and cellular slime molds
• Plasmodial slime molds
spend most of their lives as
a plasmodium
– A streaming multinucleated
mass that feeds on
microbes and organic
matter
– Undergoes mitosis many
times without cell division
– Develops into spore-bearing
fruiting bodies
Phylum: Sarcodina
• Unicellular
• Have pseudopodia =
“false foot” which is
an extension of the
cytoplasm
• Pseudopodia for
locomotion & feeding
• Reproduce asexually
• Most are free-living,
some parasitic
• Found in soil, marine
and freshwater
Amoebas
Amoeba Structure
Amoeba locomotion &
feeding
• Endocytosis
(Phagocytosis)
• Digestion by
enzymes
• Distinguish
between food and
non-food
Recap
• Protists represent
the kingdom where
evolutionary
adaptations allowed
for the development
of plants, fungus,
and animals from
single-celled
bacteria.
• Protists have
numerous
characteristics that
allow for grouping.
• Some protists are
good for us: provide
nutrients,
photosynthesize, etc.
• Some protists cause
disease: malaria,
African sleeping
sickness, giardiasis.