Kingdom Protista

1
Kingdom Protista

• Characteristics
• Algaelike or plantlike
• Protozoa or Animallike
• Funguslike
• Unicellular
• Multicellular
• Eukaryotes

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Kingdom ProtistaAlgaelike or Plantlike

• All obtain energy by photosynthesis.
• All have chlorophyll a, but may have various
  other chlorophylls and different accessory
  pigments.
• Phyla
• Euglenophyta
• One to three flagella, at their apical (leading)
  end
• Dinoflagellates
• Two flagella- one is posterior, while the second
  is transverse and rest in an encircling mid
  groove perpendicular to the first flagellum.
• Some are bioluminescent.
• Others produce nerve toxins that concentrate in
  filter-feeding shellfish, which then cause
  illness in human when eaten.

3
Kingdom ProtistaAlgaelike or Plantlike

• Phyla
• Chrysophyta
• Golden algae
• Have one or two apical flagella
• Diatoms
• Shells made of silica (SiO2)
• Chlorophyta
• Green algae
• Have both chlorophyll a and b
• Cellulose cell walls
• Store their carbohydrates as starch
• Believed to be the ancestors of plants
• Variation in sexuality.

4
Kingdom ProtistaAlgaelike or Plantlike

• Phyla
• Phaeophyta
• Brown algae
• Multicellular
• Have flagellated sperm cells.
• Some are giant seaweeds or kelps

5
Kingdom ProtistaProtozoa or Animallike

• Heterotrophs
• Consume either living cells (being predatory or
  parasitic) or dead organic matter.
• Phyla
• Rhizopoda
• Amoebas
• Move by extensions of their of their cell body
  called pseudopodia.
• Pseudopodia encircle food and absorb it by
  phagocytosis

6
Kingdom ProtistaProtozoa or Animallike

• Phyla
• Zooflagellates
• Flagellated protozoa
• Some mutualistic species digest cellulose in the
  guts of termites.
• Others are parasites, such as Trypanosoma, which
  is transmitted by the tsetse fly and cause
  African sleeping sickness in humans.

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Kingdom ProtistaProtozoa or Animallike

• Phyla
• Sporozoa
• Parasites of animals
• No physical means of motility
• They form spores which are dispersed by one or
  more hosts that participate in the completion of
  their life cycle
• Sporozoan that causes malaria, spends part of its
  life cycle in mosquitoes and part in humans.

8
Kingdom ProtistaProtozoa or Animallike

• Phyla
• Ciliophora
• Distinguished by their cilia, which they use for
  moving.
• Specialized structures
• Mouth
• Anal pore
• Contractile vacuoles for water balance
• Two kinds of nuclei (macronucleus and several
  small micronuclei)
• Paramecium

9
Kingdom ProtistaFunguslike

• Resemble fungi because they form either filaments
  or spore-bearing bodies similar to fungi.
• Three divisions

10
Kingdom ProtistaFunguslike

• Acrasiomycota (cellular slime molds)
• Exhibit both funguslike and protozoalike
  characteristics during their life cycle.
• Spores germinate into amoebas which feed on
  bacteria.
• When food sources are depleted, the amoebas
  aggregate into a single unit, which migrates as a
  slug.
• The individual cells of the slug then mobilize to
  form a stalk with a capsule at the top similar to
  the spore-bearing bodies of many fungi.
• Spores are then released, which repeat the cycle
  when they germinate.

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Kingdom ProtistaFunguslike

• Myxomycota (plasmodial slime molds)
• Grow as a single, spreading mass (plasmodium)
  feeding on decaying vegetation.
• When food becomes unavailable or when the
  environment desiccates, stalks bearing spore
  capsules form.
• Haploid spores released from the capsule
  germinate into haploid amoeboid or flagellated
  cells which fuse to form a diploid cell.
• The diploid cell grows into the spreading
  plasmodium.

12
Kingdom ProtistaFunguslike

• Oomycota (water molds, downy mildew, and white
  rust)
• They are either parasites or saprobes.
• They are much like fungi in that they form
  filaments (hyphae) which secret enzymes that
  digest the surrounding substances.
• The breakdown products of digestion are then
  absorbed.

13
Kingdom ProtistaEvolution of Eukaryotes

• Cellular structures and processes unique to
  eukaryotes
• Membrane-enclosed nucleus
• Mitochondria
• Chloroplasts
• Endomembrane system
• Cytoskeleton
• Multiple chromosomes consisting of linear DNA
  molecules compactly arranged with proteins.
• Life cycles that include mitosis, meiosis, and
  sex.

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Kingdom ProtistaEvolution of Eukaryotes

• First process in eukaryotic evolution
• Specialized infoldings of the prokaryotic plasma
  membrane, may have produced
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus

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Kingdom ProtistaEvolution of Eukaryotes

• Second process in eukaryotic evolution
• Endosymbiosis hypothesis, Lynn Margulis,
  University of Massachusetts
• Probably led to the mitochondria and chloroplast
• Proposes that mitochondria and chloroplast were
  formerly small prokaryotes living within larger
  cells.
• Proposed ancestors of mitochondria were aerobic
  heterotrophic prokaryotes that became
  endosymbionts.
• Proposed ancestors of chloroplasts in early
  eukaryotes were photosynthetic prokaryotes,
  probably cyanobacteria, that became endosymbionts.

16
Kingdom ProtistaEvolution of Eukaryotes

• Evidence (mitochondria/chloroplast to bacteria)
• Endosymbiotic relationships in the modern world.
• Appropriate size
• Inner membranes have several enzymes and
  transport systems that resemble those found on
  the plasma membrane of modern prokaryotes.
• Replicate by a splitting process similar to
  binary fission in bacteria.
• Contain a genome consisting of circular DNA not
  associated with histones or other proteins.

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Kingdom ProtistaEvolution of Eukaryotes

• Evidence (mitochondria/chloroplast to bacteria)
• Contain transfer RNA, ribosomes, and other items
  needed to transcribe and translate their DNA into
  proteins.
• Ribosomes are more similar to prokaryotic
  ribosomes.
• Size
• Biochemical characteristics
• Sensitivity to certain antibiotics
• Lang and Burger, University of Montreal
• Found that mitochondrial genome of the protist
  Reclinomonas americana closely matches that of
  bacteria in structure and function.