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Chapter 22

Chapter 22. Protists. Protists. Simplest eukaryotic cells Eukaryotic characteristics Nucleus and other complex organelles Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs” More than one chromosome Protozoans Algae Fungi Plants Animals.

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Chapter 22

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  1. Chapter 22 Protists

  2. Protists • Simplest eukaryotic cells • Eukaryotic characteristics • Nucleus and other complex organelles • Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs” • More than one chromosome • Protozoans • Algae • Fungi • Plants • Animals

  3. Protists • Very diverse! • Some may resemble plants, fungi, or animals • Lack complexity of “higher” organisms • Protozoa—“first animal”

  4. Protists • Taxonomy questionable & confusing • Traditionally organized by motility • Amoeboid • Cilliate • Flagellate • Sporozoans • Organize by evolutionary relationship • Parabasalids & diplomonads • Euglenoids & kinetoplastids • Radiolarians & foraminiferans • Alveolates & streamenophiles • Amoebozoans

  5. Protozoal Movement • Flagella—long outer structures for movement • Usually only a few • Cilia—short outer structures for movement • Usually many • “Hair-like” • Pseudopod • “False foot”

  6. Amoeboid Protozoans • Amoeba proteus • “Classic” amoeba • Predatory • Pseudopods • See it move! • Entamoebahistolytica • Found in contaminated water • Causes diarrhea • 50 million cases annually • 100,000 deaths annually

  7. Amoeboid Protozoans • Foraminiferans • Form shells • Mostly calcium carbonate • Pseudopods protrude through holes (foramen) in shells • Over long spans, form chalk & limestone

  8. Amoeboid Protozoans • Radiolarians • Form shells • Perforated • Short silica rods • Numerous short, stiff pseudopods • Part of plankton

  9. Ciliate Protozoans • Most free-living heterotrophs • Feed on algae, bacteria, each other • 1/3 symbionts or parasites

  10. Ciliated Protozoans • Paramecium • “Typical” ciliate • Cilia sweep water w/ food into gullet • Macronucleus & micronucleus • Micronucleus has full genome but doesn’t transcribe

  11. Ciliate Protozoans • “Sexual” & asexual reproduction (Fig 22.8) • Physical contact, cytoplasmic fusion • Micronucleus undergoes meiosis • One 2n micronucleus  Four n micronuclei • 3 of 4 mironuclei dissolve • Remaining micronucleus undergoes mitosis, making 2 micronuclei • Cells exchange one micronucleus • Cells separate • Original macronucleus dissolves • Micronuclei divide (making 4) • Two micronuclei develop into macronuclei • Cell divides

  12. Ciliate Protozoans • Stentor • Filter feeder • One of largest single-celled organisms • Several millimeters! • Cilia around mouth create current • See it in action!

  13. Ciliate Protozoans • Didinium • Free-living predators • Two rings of cilia • Mostly feed on Paramecium • Toxin paralyzes prey’s cilia • Can live in cysts for 10 years • See it hunting! • Longer, but has great close-up!

  14. Flagellate Protozoans • Kinetoplastids • Mitochondria almost as long as body • Trypanosomabrucei • African sleeping sickness • Transmitted by tsetse fly • Enters spinal fluid & brain

  15. Flagellate Protozoans • Euglenoids • 1/3 Heterotrophs • 2/3 Photoautotrophs • Eye spot (stigma) • Detects light • Euglena

  16. SporozoanProtozoans • No structures for movement • All are parasitic • Complex life cycles • Multiple hosts

  17. SporozoanProtozoans • Plasmodium • Causes malaria • Most widespread parasite of humans • Disease in 515 million people annually • US population is 300 million • 5 million infected with HIV annually • Kills 1-3 million people annually • 2.8 million AIDS deaths annually • Transmitted by female Anopheles mosquito • No vaccine

  18. SporozoanProtozoans • Toxoplasmagondii • May be 60 million infections in US • “Fecal-oral” route • Cat feces contaminating hands, water, or utensils • Most infections have no symptoms • Some people show flu symptoms • Immunosuppression increases infection risk

  19. SporozoanProtozoans • Toxoplasmagondii (cont.) • Can cause serious disease in fetus if mother infected • ONLY if is mother’s first exposure • Can affect host behavior • May be a cause of schizophrenia • Cats shed cysts for a few weeks after first infection

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