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Protistans

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Protistans

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  1. Protistans Chapter 22

  2. Protistans are Unlike Prokaryotes • Have a nucleus and organelles • Have proteins associated with DNA • Use microtubules in a cytoskeleton, spindle apparatus, and cilia and flagella • May contain chloroplasts • May divide by mitosis and meiosis

  3. Difficult to Classify • Historically a catch-all kingdom • Differ enormously from one another in morphology and life-styles • Molecular and biochemical comparisons are clarifying the evolutionary picture • Protistans are not a monophyletic group

  4. Evolutionary Tree branch leading to plants branch leading to fungi branch leading to animals charophytes green algae amoeboid protozoans Stramenopiles Alveolates red algae brown algae ciliates chrysophytes sporozoans oomycotes ? dinoflagellates “crown” of eukaryotes (rapid divergences) slime molds euglenoids kinetoplastids parabasalids (e.g., Trichomonas) diplomonads (e.g., Giardia) Endosymbiotic origins from prokaryotic ancestors Figure 22.02Page 366

  5. Euglenoids: Evolutionary Puzzle • Some heterotrophs • Most have chloroplasts like green algae and plants • Have flagella like flagellated protozoans • Related to flagellated protozoans • Acquired chloroplasts by endosymbiosis

  6. Euglenoid Body Plan Figure 22.3 Page 365 long flagellum contractile vacuole chloroplast eyespot nucleus nucleus ER Figure 22.3Page 365 Golgi body mitochondrion pellicle

  7. Euglenoids Are aMonophyletic Group • Members share a common ancestor and derived traits that are present in no other group • Unique traits • A storage carbohydrate • Type of eyespot

  8. Flagellated Protozoans • Have one or more flagella • All are heterotrophs • Euglenoids • Kinetoplastids (include trypanosomes) • Parabasalids (include trichomonads) • Diplomonads (include Giardia)

  9. Trypanosomes (Kinetoplastids) undulating membrane mitochondrion basal body of flagellum free flagellum nucleus • Trypanosoma brucei causes African sleeping sickness • T. cruzi causes Chagas disease Figure 22.4Page 368

  10. Trichomonads (Parabasalids) Trichomonas vaginalis causes trichomoniasis, a sexually transmitted disease Do not post photos on Internet Figure 22.5aPage 368

  11. Giardia (a Diplomonad) • Internal parasite of humans, animals • Survives outside of body as cysts • Ingested cysts release trophozoites that attach to intestinal lining • Causes giardiasis

  12. Amoeboid Protozoans (Sarcodina) • Move by means of cytoplasmic streaming and pseudopods • Naked amoebas • Foraminiferans • Heliozoans • Radiolarians Rhizopods Actinopods

  13. Naked Amoebas • Change shape constantly • Most are free-living cells that engulf their prey • Some are symbionts in animal guts • A few are opportunistic pathogens

  14. Other Amoeboid Protozoans • Foraminiferans • Calcium carbonate shell • Radiolarians and Heliozoans • Shells of silica A living heliozoan Do not post photos on Internet Figure 22.6cPage 369

  15. Alveolates • Have tiny, membrane-bound sacs (alveoli) underneath their outer membranes • Ciliates • Sporozoans • Dinoflagellates

  16. Ciliates (Ciliphora) • All heterotrophs • Arrays of cilia allow movement and direct food into oral cavity • Diverse life-styles Do not post photos on Internet Paramecium Figure 22.7cPage 370 Hypotrich

  17. Body Plan of Paramecium food vacuole food residues being ejected gullet cilia trichocysts (“harpoons”) contractile vacuole emptied contractile vacuole filled micronucleus macronucleus Figure 22.7aPage 370

  18. Ciliate Conjugation • Most ciliates have two different nuclei • Large macronucleus • Smaller micronucleus • Micronucleus participates in sexual reproduction (conjugation) • Partners exchange micronuclei

  19. Sporozoans • Parasitic • Complete part of the life cycle inside specific cells of a host organism • Many have elaborate life cycles that require different hosts • Many cause serious human disease

  20. Cryptosporidium • Motile infective stage (sporozoite) invades intestinal epithelium • Causes cramps, watery diarrhea • Commonly transmitted by water contaminated with cysts

  21. Toxoplasma • Cysts may be ingested with raw or undercooked meat • Exposure to cysts from cat feces • Symptoms are usually mild in people with normal immune function • Infection during pregnancy can kill or damage the embryo

  22. Malaria • Most prevalent in tropical and subtropical parts of Africa • Kills a million Africans each year • Caused by four species of Plasmodium • Transmitted by Anopheles mosquitoes

  23. Plasmodium Life Cycle sporozoites sporozoites Gametes form in mosquito gut, combine to form zygotes merozoite Offspring enter blood, cause malarial symptoms Male and female gametocytes in blood Figure 22.11Page 373

  24. Dinoflagellates • Most are single photosynthetic cells • Important component of phytoplankton • Each has two flagella • Algal bloom is population explosion of dinoflagellates

  25. Pfiesteria piscicida • Associated with large fish kills • Complicated life cycle • Population explosions tied to water pollution

  26. Stramenopiles • Unique trait is one of their two flagella has thin filaments projecting from it • Cells have four outer membranes • Include • Oomycotes • Chrysophytes • Brown algae

  27. Oomycotes • Large egg cell forms inside oogonium • Saprobic decomposers, parasites, pathogens • Water molds • Downy mildews • White rusts • Phytophthora

  28. Phytophthora • Plant pathogens • Phytophthora infestans Late blight of potatoes • Phytophtora ramorum Sudden oak death Do not post photos on Internet Figures 22.14, 22.15Page 375

  29. Chrysophytes (Chrysophyta) • Mainly free-living photosynthetic cells • Contain chlorophylls a, c1, and c2 • Four groups: - Golden algae - Diatoms - Yellow-green algae - Coccolithophores

  30. Diatoms • Major component of the phytoplankton • Silica shell of two overlapping parts • Sediments rich in diatom remains quarriedfor many uses Do not post on Internet Figure 22.16cPage 376

  31. Coccolithophores • Major component of the phytoplankton • Calcium carbonate shell • Remains in chalk and limestone deposits Do not post on Internet Coccolithophore shell Fig. 22.16d,ePage 376

  32. Brown Algae (Phaeophyta) • 1,500 species • Most abundant in temperate seas • Contain chlorophylls a and c, and fucoxanthin • Range in size from tiny filaments to giant kelps Macrocystis Figure 22.17 Page 377

  33. Green Algae (Chlorophyta) • 7,000 species • Resemble plants • Chlorophylls a and b • Starch grains in chloroplasts • Cell walls of cellulose, pectins Ulva Fig. 22.18Page 378

  34. Red Algae (Rhodophyta) • 4,100 species • Most abundant in tropical seas • Can grow at great depths (phycobilins) • Complex life cycles may include very different forms

  35. Plasmodial Slime Molds • Myxomycota • Cell walls break down during aggregation • Plasmodium migrates, then differentiates to form spore-bearing structures