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Protists

Protists. Chapter 28. In the beginning…. van Leeuwenhoek when observing protozoa: “no more pleasant site has met my eye than this” (1681) “My excrement being so thin I was…persuaded to examine it. I have sometimes seen animalcules a-moving very prettily…” (a bad week in 1681).

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Protists

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  1. Protists Chapter 28

  2. In the beginning… • van Leeuwenhoek when observing protozoa: • “no more pleasant site has met my eye than this” (1681) • “My excrement being so thin I was…persuaded to examine it. I have sometimes seen animalcules a-moving very prettily…” (a bad week in 1681)

  3. Understanding the Protista • For this class we will focus on: • How they are categorized • General features of protozoa • Exceptions to the general features • Examples of sexual reproduction • Specific species from several, not all, clades of protists (good reason to attend lecture)

  4. Protista

  5. Protists – the first eukaryotes • Protozoa • Algae (unicellular and colonial) • Algae (large – seaweeds, kelp) • Diatoms • Water molds

  6. A model for the formation of eukaryotic cells: Endosymbiosis

  7. A model for diversity in Protists: Endosymbiosis again

  8. Protists – the first eukaryotes • Greater cellular complexity than in prokaryotes • The most nutritionally diverse of all eukaryotes • Photoautotrophs • Heterotrophs • Mixotrophs • Ecology • Protozoa (ingestive, animal-like) • Fungus-like (absorptive) • Algae (photosynthetic, plant-like) Golden algae

  9. General Features • Unicellular and multicellular • Colonial and true multicellular • Free-living and parasitic • Most complex unicellular organism • Sexual and asexual reproduction

  10. Euglena: autotrophs but can become heterotrophic (mixotrophs)

  11. A sampling of protists Giardia Euglena Amoeba Trypanosoma

  12. A sampling of protists Diatoms, algae – primary productivity in aquatic and marine systems Unicellular Colonial Multicellular

  13. A sampling of protists Red Algae Kelp Golden Alga Nori (red alga)

  14. Diplomonads and Parabasalids • Giardia intestinalis • Water borne parasite • Common in backcountry • Anaerobes • Harm host by mechanical blockage of gut • Trichomonas vaginalis • Sexually-transmitted parasite • Outcompetes in disturbed area • Can acquire helpful gene from bacteria • Males asymptomatic

  15. Euglenozoans – just listen • Kinetoplastids – Trypanosomes • Cause sleeping sickness (Africa), Chagas disease (Central and S. America) • Antigenic variation in surface proteins • 1/3 of genome codes for surface antigens

  16. Alveolates • Dinoflagellates • Phytoplankton • Can cause “red tide” • Toxins can sicken or kill humans Pfiesteria shumwayae

  17. Alveolates • Apicomplexans • Parasitic • Complex life cycle • Cause of malaria • Know this life cycle!

  18. Malaria • Sporozoites infect liver cells • Merozoites burst from liver • Infect RBC’s, eat and reproduce in cycle • Gametocytes produced • Mosquito takes a meal • Zygote moves to hemocoel • Produces sporozoites • Injected into next victim

  19. Stramenopiles – just listen • Oomycetes – water molds • Look at your dead goldfish • Diatoms – unicellular algae with silica wall • Diatomaceous earth • Golden algae

  20. Stramenopiles • Brown algae • Seaweed • Complex multicellular • Seaweed body is a thallus with: • Rootlike holdfast • Stemlike stipe • Leaflike blades

  21. Alternation of generations

  22. Amoebozoans • Entamoebas • All in genus Entamoeba are parasitic • E. histolytica (“tissue lysis”) • Causes amoebic dysentery (bloody diarrhea) • 100,000 deaths worldwide/yr

  23. Amoebozoans • Slime molds, 2 kinds: • Plasmodial • Forms a unicellular, multinucleate mass (plasmodium) • Cellular • Individual amoebas come together to form a multicellular organism

  24. Red and Green Algae • Red algae • Similar to seaweeds (brown algae) • Green algae • Uni- and multicellular • Colonial types (Volvox) • Symbionts with fungi (lichens) • Close relatives to land plants

  25. Chlamydomonas nivalis “green” algae

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