Introduction to Protists (Ch 28)

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Introduction to Protists(Ch 28)

• Rusteen Honardoost
• Ravi Venkataraman
• Eric Ling
• Bogu Wei

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What are protists?

• The simplest eukaryotic organisms, yet are the
  most complex at a cellular level.
• Are the ancestor to all eukaryotes.
• The oldest fossils of protists are acritarchs
  (2.1 billion years old!)

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Different Life Cycles of a Protists

• The Types       

• Most protists are mobile.
• Mitosis occurs in most protists but with
  variations. Most reproduce asexually.
• Protists can shuffle genes using syngamy
• Some protists dont fit the basic life cycle
  patterns.
• CYSTS resistant protists which survive harsh
  conditionsgaining ability through time.
• Plankton make 50 of photosynthetic production in
  the world.

Heterotrophs
Phototrophs
Protozoa
Algae
Mixotrophs
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Endosymbiotic Theory how did compartmental
organization evolve in eukaryotes?

Natural selection favored complexity in some
animals through 3 trends

• Endomembrane system certain organelles evolved
  from the plasma membrane.
• Endosymbiosis creation of organelles through
  absorption of prokaryotes by eukaryotes (ex
  mitochondria and chloroplasts)
• Why?
• Because of appropriate size, similar enzymes to
  prokaryotes plasma membranes, circular DNA, no
  histones.

Evolution of multicellular prokaryotes
Evolution of complex communities of prokaryotes
Compartmentalization of cell functions
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Protist Taxonomy

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Archaezoa and Euglenozoa

• Have no mitochondria because they are the most
  ancient protists.
• Diplomonads subgroup of archaezoa with 2 nuclei
• Ex parasite Giardia lambia

• 2 groups euglenoids, kinetoplastids
• Euglenoids anterior pocket with flagella,
  mixotrophic or heterotrophic
• Kinetoplastids have a single large mitochondria
  associated with the kinetoplast (which houses
  extracellular DNA). They are symbiotic pathogens.

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Amoebas, Actinopods, and Forams

• All use pseudopedia (cellular extensions) to move
  and feed.
• Amoebas
• Live in secreted protein shells. They produce
  asexually (no meiosis) they live everywhere.
• Actinopods
• They are planktonic. There are 2 types helizoans
  (freshwater) and radiolarians (colonial)
• Forams
• They are marine animals, living in sands, with
  multi-chambered shells. Most are fossils.

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Slime Molds

• Plasmodial
• Heterotrophic, brightly colored, eat using
  plasmodium, diploid nuclei, used to study mitosis.

• Cellular
• Cell remain separate by mem-branes, haploid,
  asexual repro-duction, no flagellate stages