3/3/2011
Protists
Protists
• Eukaryotes
• Not a monophyletic group
– Paraphyletic
March 3rd, 2011
• Still use the term “protist”
– All eukaryotes except Plants, Fungi, Animals
Protist Body Plans
• Most unicellular
• Some colonial
• Some multicelled
• Blurry lines separating these
– Different life stages can appear differently
Protist Feeding Strategies
• Photoautotrophs
– Chloroplasts
• Heterotrophs
• Mixotrophs
– Can do photosynthesis and eat food
• Three feeding approaches have arisen independently multiple times
Protist Reproduction
• Very diverse
• Use all three ↓
Endosymbiosis
• Mitochondria (proteobacteria)
• Chloroplasts (cyanobacteria) = plastids
• Secondary endosymbiosis
– One eukaryote phagocytized by another
• Evidence: Other reproductive strategies that don’t fit
Nucleomorph (vestigial nucleus)
More membranes (up to 4)
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Protist Systematics
• Kingdom Protista abandoned
• Some “protists” found to be fungi, plants, or animals
• 5 “supergroups”
“
”
Present phylogeny is tentative, hypothetical, wrong
– A lot left to learn
Excavata
• Linked by cytoskeletal morphology
• Some have “excavated” feeding groove
• Three Groups
– Diplomonads
– Parabasalids
– Euglenozoans
Excavata
• Diplomonads
– Lack Plastids
– Modified Mitochondria (reduced)
• No electron transport chain
No electron transport chain
• Mostly anaerobic environments
– 2 equal‐size nuclei and multiple flagella
– Many are parasites
Excavata
• Parabasalids
– Lack Plastids
– Modified Mitochondria (reduced)
• No electron transport chain → H
No electron transport chain → H2 gas released
gas released
• Mostly anaerobic environments
Trichomonas vaginalis
– Flagella
– Many are parasites
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Excavata
• Euglenozoans
Excavata
• Euglenozoans
– Flagella have spiral or crystalline rod
Kinetoplastids
– Have single large mitochondrion
Predators, photosynthesis, Predators
photosynthesis
parasites
– Kinetoplastids
– Euglenids
• Contains an organized mass of DNA
Contains an organized mass of DNA
– Predators (prokaryotes)
– Parasites (eukaryotes)
– Trypanosoma
Surface proteins change
Excavata
• Euglenozoans
Euglenids
– Have one or two flagella Many mixotrophs
Chromalveolates
• Genetic Data suggests monophyly
• Secondary endosymbiosis of a red alga
• Controversial
– Some lack plastids and have no plastid genes
Two main groups
– Alveolates and Stramenopiles
Chromalveolates
• Alveolates
Chromalveolates
• Alveolates
– Monophyly well‐supported
Dinoflagellates
– Alveoli (membrane‐bound sacs) below plasma membrane
–
–
–
–
–
• Unknown function
Unknown function
– Dinoflagellates
– Apicocomplexans
• Parasites
– Ciliates
Cellulose plates for reinforcement
Two flagella in grooves
Two
flagella in grooves
Spin
Auto‐, hetero‐, mixotrophs
Blooms
• Red tide (carotenoids)
• Toxins
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Chromalveolates
• Alveolates
• Alveolates
Apicocomplexans
Apicocomplexans
–
–
–
–
Chromalveolates
Mostly parasites
Apex contains complex
contains complex for burrowing into hosts
for burrowing into hosts
Retain modified plastid
Complex life cycles
– Plasmodium causes malaria
Chromalveolates
• Alveolates
Chromalveolates
• Alveolates
Ciliates
Ciliates
– Video
– Contain macronuclei Contain macronuclei
and micronuclei
Chromalveolates
• Stramenopiles
– Marine algae
– Photoautotrophs and heterotrophs
– “Hairy”
Hairy flagella
flagella
Chromalveolates
• Stramenopiles
Diatoms
– Unicellular
– Wall of SiO
Wall of SiO2, overlap
overlap
– Most reproduction asexual
– Important marine and freshwater plankton
– May use diatoms to fight global warming
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Chromalveolates
• Stramenopiles
Chromalveolates
• Stramenopiles
Golden Algae
– Yellow and brown carotenoids
– Biflagellate
– Photosynthetic, mixotrophic
– Most unicellular, some colonial
Brown Algae
– Large (60m) and complex
– Multicellular
– Some specialized tissues
– Thallus
• Holdfast
• Stipe
• Blades
Chromalveolates
• Stramenopiles
Oomycetes
– Previously classified as fungi
Chromalveolates
• Stramenopiles
Oomycetes
• Hyphae
– Cellulose cell walls
• Chitin in fungi
– No plastids
– Decompose or parasitize
– Phytophthora
Alternation of Generations
• Multicellular haploid and diploid stages
– Heteromorphic or isomorphic
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