Kingdom Protista
Kingdom Protista
• Kingdom Protista - 65,000-200,000 species
(est.), fr. Greek protos = first, ktistos =
established - algae, protozoans
• Also called Kingdom Protoctista
• Taxonomic “grab bag”, primitive organisms
only distantly related (polyphyletic)
Kingdom Protista
• All protists are eukaryotes
• All protists are aquatic
• Unicellular or multicellular
• Some are colonial - cells specialize in
different function (feeding, reproduction) =
division of labor, communication
Kingdom Protista
• Some are autotrophs = algae
• Some are heterotrophs = protozoa
• Reproduce either sexually or asexually
(by binary fission)
• Complex life cycles
Kingdom Protista
• Protists are so small they don’t need special
organs to exchange gas or excrete wastes
• They rely on diffusion - passive movement
of molecules from area of higher
concentration to area of lower concentration
• Diffusion results from the random
movement of molecules
Kingdom Protista
• Diffusion is a two edged sword
• Protists don’t need to invest in complex
respiratory or excretory tissue
• They have to stay tiny - diffusion only
works if you’re very small
• Most protists are single cells
Kingdom Protista
• Size is also limited by means of locomotion
• Many protists are propelled by cilia or
flagella, tiny movable hairs
• Protists eat by phagocytosis
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Engulf food in cell membrane
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Pinch off membrane to form a vacuole
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Vacuoles store food, water, enzymes, wastes
Phagocytosis
Didinium devours Paramecium
Kingdom Protista
• All of these traits are primitive - similarities
may be due to convergent evolution
• Protists are mainly defined by what
they are not
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Not bacteria, archaea, or fungi…
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Not plants or animals…
Kingdom Protista
• Protists gave rise to all other plants and
animals
• Phylogeny of protists still a real mess
• We assume they rose from certain groups of
archaeans, but which?
Kingdom Protista
• Protists are so different from one another,
most may represent several early
independent lineages of eukaryotes
• First evolved ~ 1.2 billion years ago
• As many as 50 phlya recognized
• We’ll focus on several typical phyla
Kingdom Protista
• Protozoa - heterotrophs
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Motile
– Cilia – Ciliophora
– Flagella – Dinoflagellata, Euglenozoa
– Pseudopodia – Amoebozoa, Foraminifera
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Non- motile - Apicomplexa
• Gave rise to higher animals
Kingdom Protista
Phylum Euglenozoa
• 800 sp. - Euglena
• Plant or animal? Heterotrophs, but 1/3d are
also photosynthetic
• May have formed by endosymbiosis,
engulfed green algae cell
Euglena
Euglena
Kingdom Protista
Phylum Dinoflagellata
• Dinoflagellates - 3,000 species, fr. Greek
dinos = whirling, Latin flagellum = whip Ceratium, Gonyaulax
• About half are photosynthetic
Dinoflagellates
Kingdom Protista
Phylum Dinoflagellata
• Two flagella, one like a belt, one like a tail
• Many have armor of cellulose plates
encrusted with silica
Dinoflagellates
Kingdom Protista
Phylum Dinoflagellata
• Importance
>
Zooxanthellae, dinoflagellates that have lost
flagella & armor, live as symbionts in mollusks,
sea anemones, jellyfish, coral
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Make coral more productive, limits coral to
shallow water
Kingdom Protista
Phylum Dinoflagellata
• Importance
>
Algal blooms of dinoflagellates are the cause of
red tide - 20 species produce potent toxins
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1987 outbreak killed half the Western Atlantic
population of bottlenose dolphin!
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Could make La. oysters an unforgettable
experience…
Red Tide 2010 Breton-Chandeleur
Kingdom Protista
Phylum Apicomplexa
• Apicomplexa are spore-forming parasites
• One end has an apical complex, apparatus
designed to let them invade a host cell
• Sometimes called sporozoans, many form
non-motile spores
Kingdom Protista
Phylum Apicomplexa
• Plasmodium – causes malaria
• Spores are passed from one host to the next
by vectors (mosquitoes etc.)
• Typical parasite life cycle, with intermediate
hosts
Kingdom Protista
Phylum Ciliophora
• 8,000 species, fr. Latin cilium = eyelash,
Greek phorein = to bear - Paramecium,
Blepharisma
• Complex little critters - many organelles
and specialized structures
Blepharisma
Kingdom Protista
• Paramecium (and many other protists) have
a contractile vacuole
• Complex vacuole that drains wastes from
the cell
Contractile Vacuole of Paramecium
Kingdom Protista
Phylum Ciliophora
• Move by numerous cilia
• Many ciliophorans defend themselves by
discharging little toxic threads or darts
Paramecium, with cilia stained
Kingdom Protista
Phylum Ameobozoa
• Over 300 species – true amoeba
• Move by pseudopods - extend part of cell to
form a “false foot”, then flow into it
(cytoplasmic streaming)
• Eat other protozoans, algae, even tiny
multicellular creatures
Amoeba
Kingdom Protista
Phylum Ameobozoa
• Many amoeba are parasites
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Entamoeba histolyca - amoebic dysentery,
infects ~10 million Americans, 50% of
population in the tropics
Kingdom Protista
Phylum Ameobozoa
• Many amoeba are parasites
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Primary Ameobic Meningoencephalitis (PAM)
Naegleria fowleri enters the nostrils (frequently
during swimming), attacks the brain, can be
fatal within one week of symptoms
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PAM is relatively rare -120 U.S. cases in 25
years
Kingdom Protista
Phylum Ameobozoa
• PAM cases include two people in La. in
2011 who died from nasal irrigation with
infected water (has to go way up the nose)
• PAM killed a 4 year old child in LA in 2013
who got it from playing on a Slip ‘n Slide
• Later found in the municipal water supply
in Arabi and Violet (a first) – easily killed
by chlorination
Kingdom Protista
Phylum Foraminifera
• Foraminifera
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Marine forms, sculpted shells (calcium
carbonate)
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Extend cytoplasmic podia out along the spines
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Spines function in feeding, swimming
Kingdom Protista
Phylum Foraminifera
• Importance
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So abundant, they formed most of the world’s
limestone, marble, and chalk
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Great Pyramids composed of billions upon
billions of foraminiferan shells
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Abundant in fossil record, used by geologists to
help identify layers of rock - indicator species
Foraminiferan shells
Great Pyramids of Egypt
Kingdom Protista
• Algae – autotrophic protists
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Photosynthetic
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Many referred to as “seaweeds”
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Gave rise to higher plants
• Phaeophyta, Bacillariophyta, Rhodophyta,
Chlorophyta
Brown Algae - Fucus - rockweed
Kingdom Protista
Phylum Phaeophyta
• Brown algae - 1,500 species, fr. Greek
phaios = brown - Fucus, Sargassum, kelp
• Mostly marine
Kelp
Kingdom Protista
Phylum Phaeophyta
• Largest protists, kelp up to 100 meters long
• Blades lack conducting tissue, rely on
diffusion - can be large but must be thin
Brown Algae - Kelp
Brown Algae - Saccorhiza polyschides
Kingdom Protista
Phylum Phaeophyta
• Importance
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Kelp forms the basis for major ecosystem along
the Pacific Coast and in other cool waters
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Sargassum forms large floating mats in the
Atlantic, northeast of the Caribbean, a major
ecosystem - Sargasso Sea once thought to trap
ships
Kelp
Kingdom Protista
Phylum Baccilariophyta
• Diatoms - 11,500 species
• Golden-brown pigment
Kingdom Protista
Phylum Baccilariophyta
• Abundant in freshwater and marine habitats
• Shells made of organic compounds
impregnated with silica (CD jewel case)
Kingdom Protista
Phylum Baccilariophyta
• Importance
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So abundant they account for a large percentage
of the oxygen added to the atmosphere
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Shells form deposits called diatomaceous earth,
used in abrasives, talc, and chalks
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Lompoc CA quarry - 270,000 metric tons/year,
Santa Monica bed is over 900 meters thick!
Kingdom Protista
Phylum Rhodophyta
• Red algae - 4,000 species, fr. Greek rhodos
= red - Polysiphonia, Nemalion
• Mostly marine, closely related to green algae
• Red algae dominate in salt water, green
algae dominate in fresh water
• Elaborate life cycles
Kingdom Protista
Phylum Rhodophyta
• Red algae plastids (rhodoplasts) similar to
certain cyanobacteria, acquired through
endosymbiosis
• Brown algae formed in similar fashion,
eukaryotic protist swallowed a red algae
Red Algae - Scinaia furcellata
Kingdom Protista
Phylum Rhodophyta
• Importance
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Agar from cell walls used for culture plates
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Carrageen, thickening agent also extracted from
red algae, used in making ice cream, lunch
meats, cosmetics, paint, beer and wine!
Kingdom Protista
Phylum Chlorophyta
• Green algae - ancestral to land plants
• Recently recognized as sister taxon to land
plants
• Now “bumped up” to Kingdom
Viridiplantae (algae + land plants)
Chlorophyta