Bio 2.2 Protists

  1. Level of Organization
  2. Endosymbiotic Theory of Eukaryotic Origin
    Eukaryotic fossils appear to have been formed by the fusion of two or more prokaryotes.

    Proposed by Lynn Margulis in 1970.
  3. Mitochondria were once:
    Free living "purple non-sulphur bacteria".
  4. Chloroplasts were once:
    Free living photosynthetic bacteria.
  5. What are the three ways protists move?
    • Achieved by pseudopodia:
    • Lobopodia
    • Reticulopodia
    • Axopodia
  6. Lobopodia
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    • Organism sends an extension forward containing molecules of actin and myosin which stiffen the extension. As the organism moves forward the actin and myosin in the rear are broken by enzymes and moved to the front, allowing movement of the whole organism. 

    Example: Amoeba, phagocytes in humans.
  7. Reticulopodia
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    • Thin pseudopodia that branch and rejoin together to form a network of extensions around the protozoan.

    Seen in foraminiferans: Form a CaCO_3 (calcium carbonate) shell around themselves using calcium from their environment and CO_2 from the atmosphere (white cliffs of Dover).
  8. Axopodia
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    Extensions that are filled with microtubules (arranged in a loose spiral arrangement).
  9. How do cilia and flagella work?
    • They are in the "9 + 2" arrangement (nine pairs of long tubules encircling a single pair)
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    Dynein (motor protein) uses ATP to "ratchet" back and forth across the tubulin protein subunits of microtubules.
  10. How does osmoregulation work?
    Protozoans use a contractile vacuole to get rid of excess water.

    In freshwater the organisms are always up-taking water that needs to be removed.

    A "hydrogen active transport protein" pumps H^+ ions into a vacuole while bicarbonate (HCO3^-) follows passively. This causes the concentration gradient of water inside the vacuole to decrease, resulting in water rushing into the vacuole.

    Once the vacuole begins to reach capacity it fuses with the plasma membrane and releases its contents.
  11. How is excretion performed in protozoans and how is it allowed to take place?
    Simple diffusion.

    High surface area to volume ratio.
  12. How to protists reproduce?
    Asexually by binary fission.
  13. What are the five supergroups of the kingdom Protista?
    • Excavata
    • Chromavleolata
    • Rhizaria
    • Archaeplastida
    • Unikonta
  14. What is a basal body?
    Organizes the microtubules of a flagellum.

    Structure: exactly like centrioles
  15. What is a stigma and what is its function?
    The stigma is used in Euglena to direct movement by shading, casting a shadow on the basal body of flagella.
  16. What is a pellicle?
    Protein sheath that covers the plasma membrane of Euglenas. It allows euglena to wiggle as it moves through the medium.
  17. Why do ciliates have an unusual nuclear arrangement?
    They have a macronucleus with multiple copies of its genome and a micronucleus with a single copy of its genome.
  18. What is the purpose of the macronucleus and micronucleus in ciliates?
    The macronucleus is used for day-to-day needs and the micronucleus is used during sexual recombination called conjugation.
  19. What is conjugation?
    During conjugation the micronuclei are exchanged between two ciliates, they then divide and the new genetic combinations are utilized.
  20. What do ciliates use for locomotion?
    Hundreds of cilia.
  21. What shell type do these organisms have?

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    Calcium Carbonate
  22. What shell type do these organisms have?

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    Silicon Dioxide
  23. What are apicocomplexans (plasmodium) and what do they cause?
    Non-motile parasites; malaria.
  24. What is one important character that determines if an organism is colonial?
  25. What two cell specializations do volvox organisms have?
    Directional movement and reproduction (sexual and asexual).
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Bio 2.2 Protists