Chapter 28: Protists

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Chapter 28Protists
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Eukaryote Phylogeny
Dont worry about the various branch points
Yellow boxes (top row) indicate protist kingdoms
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Protist Diversity
Paramecium
Malaria
Kelp
Giardia
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Morphological Diversity
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Morphological Diversity
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Structural Diversity
Unicellular protists are justifiably considered
the simplest eukaryote, but at the cellular
level, many protists are exceedingly complexthe
most elaborate of all cells. p. 549, Campbell
Reece (2005)
Protists exhibit more structural and functional
diversity than any other group of organisms. p.
549, Campbell Reece (2005)
Most protists are unicelluar, although there are
some colonial and multicellular species. p. 549,
Campbell Reece (2005)
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More Protist Diversity

• The terms Protist, Protozoa, and Algae have
  no taxonomic meaning
• Protists are paraphyletic in five-kingdom
  system
• Protists are mostly aerobic, motile, aquatic,
  but can be found in most damp environments
• Protists are mostly heterotrophic but also
  include autotrophs and mixotrophs, which are both
  autotrophic and heterotrophic
• Protists can be distinguished in terms of how
  they obtain nutrients into engulfers, adsorbers,
  and algae (autotrophs ? contain chloroplasts)
• There are both asexual and sexual protists
• There are protists that display no mitosis in
  diploid state as well as ones that display an
  alternation of generation
• Protists are important predators (heterotrophic
  engulfers) and producers (the algae)

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Protist Nutritional Diversity
We can divide protists (nutritionally) into
three categories p. 550, Campbell Reece (2005)
photosynthetic (plant-like) protists, or algae
(singular, alga)
ingestive (animal-like) protists, or
protozoans
and absorptive (fungus-like) protists, which
have no other general name
Also, protists can be bottom dwellers (benthic),
free floating (planktonic), or symbiotic (in/on
other organisms
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Secondary Endosymbiosis
Dont worry about names on far right
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Secondary Endosymbiosis
Consistent with the hypothesis of secondary
endosymbiosis, their plasmids are surrounded by
four membranes. The two inner membranes
originated as the inner and outer membranes of
the ancient cyanobacterium. The third membrane is
derived from the engulfed algas plasma membrane,
and the outermost membrane is derived from the
hetrotrophic eukaryotes food vacuole. p. 551,
Campbell Reece (2006)
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Eukaryote Phylogeny
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Diplomonads

• Diplomonads have greatly degenerated mitochondria
  that are not capable of supporting cellular
  respiration, including the citric acid cycle
• Unlike other protists, Diplomonads are found
  mostly within anaerobic environments
• Diplomonads have multiple nuclei and multiple
  flagella

We wont worry about Parabasalids
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Eukaryote Phylogeny
Euglenozoa includes heterotrophic engulfers,
algae, and parasitic symbionts
All have this distinctive flagella structure
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Euglenozoans
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Kinetoplastids
Kinetoplastids are parasitic euglenozoans that
possess undulating membranes
Trypanosoma are symbiotic protists that causes,
among other things, African sleeping sickness,
which is infamously spread via the bite of the
Tsetse fly
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Euglinids
Many Euglenids are mixotrophic absorbers while
others are phagocytic
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Eukaryote Phylogeny
Some dynoflagellates also exist as photosynthetic
symbionts, notably of coral polyps
Heterotrophic engulfers
Autotophic and Heterotrophic
Parasitic
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Alveolata Alveoli
All Alveolata have membrane-bound sacs called
alveoli found immediately under their plasma
membranes these are of unknown function
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Dinoflagellates
Perpendicular grooves
Cellulose plates found in many species
These cells whirl through the water
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Dinoflagellate Blooms
Excessive population growth results in blooms
called red tides than release toxins that can
kill aquatic animals, and even humans exposed to
shellfish exposed to such blooms prior to
harvesting
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Apecomplexans
Life cycle of Plasmodium, cause of malaria
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Ciliates
Stentor
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Tetrahymena spp.
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Eukaryote Phylogeny
Water molds
Multicellular algae
Planktonic algae
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Stramenopila
Stramenopila is named after these hairy flagella
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Oomycete Life Cycle
Oomycete Cellulose cell walls, motile sperm,
diploid mitotic division
Decomposers or parasites
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Diatoms
unique glass-like wall made of hydrated silica
embedded in an organic matrix. The wall consists
of two parts that overlap like a shoe box and its
lid. p. 559, Campbell Reece (2005)
Diatoms sperm (not shown) have hairy flagella
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Diatoms
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More Diatoms
Diatoms are photosynthetic, planktonic, and found
in both freshwater and marine environments
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Golden Algae
All golden algae are photosynthetic, some are
mixotrophs, most but not all are unicellular
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SeaWeed Thallus
Thallus seaweed body
Leaf analogy
Stem analogy
Root analogy
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Kelp are Brown Algae
Abundant especially in cooler waters
Yes, brown algae sperm have hairy flagella!
Kelp are giant, multicellular, greenish-brown-colo
red brown algae
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Alternation of Generations
Gametophyte generation (maker of gametes)
Sporoophyte generation (maker of spores)
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Alternation of Generations

• We use the phrase alternation of generations to
  describe organisms in which mitosis takes place
  as both diploids and haploids forming and
  alternating as multicellular organisms
• Sporophytes are diploid and make spores via
  meiosis
• Gametophytes are haploid and make gametes via
  mitosis
• Isomorphic means that the sporophyte and
  gametophyte are morphologically similar
• Heteromorphic means that the sporophyte and the
  gametophyte are morphologically dissimilar
• Isogamy is the fusion of two morphologically
  identical gametes
• Anisogamy is the fusion of two morphological
  dissimilar gametes
• Oogamy is the fusion of a motile sperm (smaller
  gamete) with a not-motile egg (larger gamete)

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Syngamy
Isogametes
Anisogametes
Oogamy
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Heteromorphic Life Cycle
Laminaria
Brown algae life cycle
A heteromorphic life cycle
Anoso-gamy
Alternation of generations
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Eukaryote Phylogeny
These are amoeba-like protists whose pseudopodia
are threadlike
Amoeba are not monophyletic!
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Foraminiferans (Forams)
All unicellular, mostly marine, mostly benthic
but some planktonic, calcium carbonate shells,
some have symbiotic algae
The chalky White Cliffs of Dover consist of
fossil forams
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Radiolarians
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Eukaryote Phylogeny
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Amoeba proteus
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Amoeboid Engulfment
A Gymnamoeba (Amoeba sp.)
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Plasmodial Slime Mold
Growth occurs via diploid mitosis that is not
followed by cytokinesis
Pseudopodia extend into substrate, feeding by
engulfment
Macroscopic but not multicellular
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Plasmodial Slime Mold Life Cycle
Meiosis if environment dries up
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Cellular Slime Mold
Dictyostelium
Note mostly haploid (mitotic haploid-only
division unusual for protist)
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Eukaryote Phylogeny
Often multicelluar, often red in color, often
adapted to to growth in deep water (where only
green and blue light penetrates), and lack
flagella throughout life cycle
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Red Algae
Shallower adapted species are greener in color
Abundant especially in warmer waters
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Eukaryote Phylogeny
Green algae are named for their grass-green
chloroplasts. In their ultrastructure and pigment
composition, these chloroplasts are much like
those of organisms we traditionally call plants.
p. 567, Campbell Reece (2005)
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Green Algae
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Chlamydomonas Life Cycle
Biflagellated
Not alternation of generations
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Ulva Isomorphic
Isogamy
An Isomorphic life cycle
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