Chapter 19: protists and eukaryotic cells

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Chapter 19 protists and eukaryotic cells

• Small creatures that help and hurt you

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Three categories of protists (older
classification)

• Protozoa
• Heterotrophic
• Lack plastids
• Non-photosynthetic
• Slime molds and oomycetes
• Seen below the dog vomit slime mold Fuligo spp.
• Non-photosynthetic
• Look like fungi but not related
• Algae (formerly put in with plants)
• Photosynthetic
• Autotrophic
• Non-motile

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Protist size

• Unicellular (Euglena)
• Colonial (Volvox)
• Filamentous (Chaetophora)
• Multicellular (Coelochaete)

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Plankton

• An ecological term to denote
• Marine organisms that float
• Phytoplankton
• Zooplankton

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Movement of protists

• Flagella
• Cilia
• Sessile

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Groups of Protists

• Unknown exact evolutionary relationships
• Probably polyphyletic (waste-basket) groups that
  dont have true genetic or evolutionary
  relationships

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Euglenoids

• Flagellated
• Have uniquely shaped mitochondria
• Contain paramylon as starch
• Some are autotrophs others heterotrophs
• Ecologically important

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Cryptomonads

• Single-celled flagellates
• Important ecologically --other plankton eat them
• Usually quite small and inconspicuous

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Alveolates (inc. dinoflagellates)

• Heterotrophs and autotrophs with different types
  of plastids
• Include things like red tide
• Very toxic ocean blooms
• Probably will be a big problem in the future with
  warmer water temps (global warming) and more
  human development

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Dinoflagellates and red tide

• Big problem for manatees and huge hit to
  Floridas tourism industry

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Another bad dinoflagellate Pfiesteria

• Huge fish kills off Carolina coast
• Probably due to hog industry washing waste into
  estuaries and ocean water
• Very, very toxic
• Neurotoxin that can kill people
• Causes Parkinsons like symptoms
• Memory loss, tremors

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Haptophytes

• Coccoliths (carbonate scales) that form great
  chalk deposits (White cliffs of Dover)
• Flagellates with golden plastids

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Stramenopiles

• From tiny flagellates to big marine algae
• Very odd grouping
• Includes oomycete, Phytophthora (the fungus that
  caused the Irish potato faminerotten potatoes
  shown here)

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Stramenopiles (continued)

• Diatoms
• Silica (glass) walled (tests)
• Diatamaceous earth

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Stramenopiles (continued)

• Giant brown algae known as kelp
• Can grow to hundreds of feet in length
• Form the great kelp forests in cold water
  currents (e.g. California coast)

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Others

• Green algae (chlorophytes)
• Ancestor to all land plants (charophycean algae0
• Red algae (rhodophytes)
• Dont produce flagellate cells

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Ecological roles of algae

• Phagotrophyparticle feeding
• Osmotrophyuptake of small dissolved nutrients
  (e.g. sugars)
• Autotrophyphotosynthesis
• Mixotrophycombinations of the above

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Phototrophy

• Some marine algae need accessory pigments to
  absorb different wavelengths of light
• E.g. fucoxanthin in brown algae
• Phycobilin in red algae
• Beta-carotene in greens

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Cell coverings

• Cellulose in green algae (which is why land
  plants have this)
• Silica
• Calcium carbonate
• Agar is a polysaccharide
• Must get from natural sources (too difficult to
  synthesize)

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Food storage

• Starch in green algae (again they are the
  ancestor to plants)
• Stains with iodine
• Oil droplets in diatoms (large source of oil)

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Asexual reproduction

• Spores produced in protists
• Red seaweeds produce monospores, nonflagellated
  cells that drift with ocean currents
• Cysts survive harsh conditions
• Zoospores are flagellated

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Endosymbiosis Origin of Eukaryotic Cells
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Evidence for Endosymbiosis

• Mitochondria and chloroplasts have their own
  distinct circular DNA
• These DNA sequences are similar to cyanobacterial
  DNA
• Some of this DNA is incorporated into nucleus
• Some amoebas have no mitochondria but have
  free-living aerobic bacteria in them (i.e. could
  be an intermediate)

Stentor (a protist) with green algae living
inside
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Evidence for Endosymbiosis (cont.)

• Chloroplasts and mitochondria have two membranes,
  the inner membrane is similar to prokaryotes
• Mitos and chloroplasts reproduce by binary
  fission, like prokaryotes

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SEX! (really life cycles)

• 3 ways of doing it
• Zygotic
• Sporic
• Gametic

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Zygotic life cycle

• Example Spirogyra
• Green algae

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Zygotic

• Only zygotes are diploid (e.g. Spirogyra)
• The rest of the plant is haploid!

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Sporic life cycle

• Large seaweed in Laminaria for example is
  sporophyte
• Microscopic gametophytes produce gametes
• Similar to land plants

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Sporic life cycle Laminaria
Lookey here gametophytes
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Gametic life cycle

• Like animals
• Fucus is an example
• Only the gametes are haploid
• In other words, there is no gametophyte

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Gametic life cycle Fucus
Lookey here NO gametophytes, just gametes