PROTISTS
Protists
• Protists: Unicellular eukaryotic organisms.
• Over 115,000 species
• Eukaryotic cells - contain membrane-bound organelles
(particularly mitichondria & chloroplasts)
• Protists & eukaryotes probably evolved from a large
eukaryotic cell ingesting a photosynthetic and oxygen
metabolizing bacteria
– Known as endosymbiotic theory
• Two major classes of protists
– Animal-like protists
– Plant-like protists
Animal-like Protists
• Phylum Ciliophora (Cilia bearing
protists)
– Aka "ciliates"
– Have cilia (short hairlike structures) on their
plasma membranes
– Cilia rapidly beat and provide propulsion for
the protist.
– Over 7000 species in this phylum.
– Example is paramecium.
Paramecium
•Large organisms ~305
micrometers long
•Important features:
•Have 2 nuclei
•Macronucleus (large)
•Micronucleus (smaller)
•Feed by forcing H2O into
Gullet forming food vacuoles
•Excrete wastes through anal
pore
•Excrete excess water
through use of contractile
vacuoles
•Move by coordinated
movement of hair-like cilia.
More Paramecium
Phylum Sporozoa
• Usually parasitic in nature
• Example is Plasmodia which causes malaria.
– One of the most deadly diseases to man
– Malaria is transmitted by the Anopheles mosquito.
Lifecycle of Plasmodia
Phylum Sarcodina
Protists with false feet
• Use extensions of cytoplasm to move and
feed.
• Extensions are called pseudopods (false feet)
– Movement is by extending pseudopod, then the
remainder of cytoplasm flows into extension.
– Feeding is done by extending 2 pseudopods around
object and engulfing object, forming a food
vacuole
• Examples are amoebas (amebas)
Amoebas
More amoebas
Plant-like Protists
• 5 phyla of plant-like protists
• Are usually photosynthetic, and also
heterotrophic.
• All are unicellular, most are motile
• Example: Phylum Euglenophyta
Phylum Euglenophyta
• Example is euglena.
• Has a flagellum, is
motile
• Is both heterotrophic &
autotrophic
• Contains chloroplasts &
is photosynthetic.
• Can become
heterotrophic in lowlight conditions
Euglena
Dinoflagellates
• Have 2 flagella for motility
• Often have a cellulose covering
Diatoms
• Most abundant form of marine algae.
• Form elaborate silicon (glass) shells to protect
themselves
• Shell is porous to allow materials in/out of the cell.
Multicellular / Other Algae
• Are not generally true multicellular
organisms, but rather "colonies"
• Show beginnings of specialized
functions / tissues
• 3 types
– Green algae
– Red Algae
– Brown algae
Green algae (Chlorophyta)
Green algae
(Chlorophyta)
•Contain chlorophyl a & b
•Most frequently found
in fresh water
•Often colonial
Volvox: a green colonial algae
Red Algae (Rhodophyta)
• Red Algae (Rhodophyta)
– Found in salt/brackish water
– Have additional pigments which give them a reddish color.
– In uncontrolled blooms, these organisms can cause serious ecological
damage
Red algeal bloom
Brown Algae (Rhodophyta)
• Brown Algae
(Rhodophyta)
– Most Plant-like
of all algae.
– Include kelps
– Can grow to
huge sizes
(100')
– Most primitive
plant like
organism to
show
alternation of
generations.
Giant Kelp Forest
Fungus like Protists:
• Fungus like Protists:
– Act as decomposers
– Often have a slimy appearance/texture,
hence their name.
– 3 types:
• Plasmodial slime molds
• Cellular slime molds
• Water molds
Plasmodial Slime Molds
• Plasmodial Slime Molds
– Can grow very large, however, is still a single cell (with
many nuclei)
– Feeding stage is called a plasmodium.
– Forms fruiting bodies under stress.
Cellular Slime Molds:
Cellular Slime Molds:
•Exists a majority of
its life cycle as an
amoeba
•In times of stress
these amoebas unite
to form a
Pseudoplasmodium,
which crawls to
another location (slug
form), and forms a
fruiting body
Water molds:
• Water molds:
– Completely aquatic
– Often
decomposers
– Sometimes
parasitic
Water mold attacking a fish