Protists
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Protists

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  • 1. Protists Classifying the Exceptions
  • 2. What are Protists?
    • Those organisms that cannot be classified as Monerans, fungi, plants or animals
    • Created as a group because of classification problems
    • Some share characteristics of more than one other kingdom
    • Example:
      • Euglena has chloroplasts & is an autotroph like plants,
      • but has no cell wall and can swim using a flagella, so also like an animal
  • 3. Characteristics of Protists
    • Almost all are unicellular
      • A few are colonies of identical cells
    • Are distinguished from unicellular Monerans because they are eukaryotes
      • Have a nuclear membrane
      • Have mitochondria and other organelles
    • A diverse group with diverse characteristics
      • some are plant-like, autotrophs  algae
      • some are animal-like, heterotrophs  protozoans
      • some are fungus-like, decomposers  slime molds
  • 4. Plant-like Protists
    • 10,000 species of plant-like protists
    • Divided into 3 phyla
      • Phylum Euglenophyta
      • Phylum Pyrrophyta
        • dinoflagelates, plankton
      • Phylum Chrysophyta
        • diatoms
  • 5. Phylum Euglenophyta
    • Most have chloroplasts - are autotrophs
    • Have a large nucleus and nucleolus
    • Have large chloroplasts
      • these disappear if the organism is placed in the dark
    • No cell wall
      • on the outer surface of the cell are spiral strips of protein which form a pellicle - give cell shape
    • Can move by changing shape
    • Have 2 flagella: one long, one short
    • Have an eye spot
      • an area of red pigment that is sensitive to light
    • A gullet opens into reservoir
    • Reproduce asexually
  • 6. Euglenoids
  • 7. Freshwater Protists
    • Euglenoids live in fresh water ponds and lakes
      • The single-celled organism is in a hypotonic solution
      • Water diffuses in by osmosis
    • No rigid cell wall
    • These organisms have to have an other means to prevent the cell membrane from bursting
    • Contractile vacuole controls water balance
      • Pumps excess water back out of the cell
  • 8. The Contractile Vacuole
  • 9. Phylum Pyrrophyta
    • Most common are dinoflagellates
    • Unicellular algae with 2 flagella 
    • Most are marine
      • Many plankton (small organisms near the surface of the ocean) are dinoflagelates
    • Mitosis is somewhat like prokaryotes
      • some scientists believe are intermediate form between prokaryotes and eukaryotes
  • 10. Dinoflagellate Characteristics
    • Most have chloroplasts with chlorophyll
      • red & yellow pigments mask the green
    • Most have a cellulose cell wall
    • Segments fit together like armor
    • Most have 2 flagella
      • One extends back from the middle of the cell - propels the organism
      • 2nd wraps around middle in a groove - vibrates causing cell to spin
    • Chromosomes are visible in dinoflagellates
    • Some produce toxins - red tide!
    • Many produce light - bioluminescence
  • 11. A Dinoflagellate
  • 12. Phylum Chrysophyta
    • Most are diatoms - live in fresh and salt water
    • Most are photosynthetic
      • Most are gold or brown from pigments other than chlorophyl
    • Most don't have flagella
    • Have cell walls with 2 overlapping halves
      • composed of pectin - a gelatinous material; also contains silica
    • Reproduce a sexually
  • 13. Diatoms
  • 14. Multi-cellular Algae
    • Many algae have multi-cellular bodies
      • Body of a multi-cellular algae = thallus
    • Once classified as plants because they have chlorophyll and perform photosynthesis
    • Now usually classified as protists because they have reproductive structures different from plants
    • Three phyla:
      • Chlorophyta = green algae
      • Rhodophyra = red algae
      • Phaeophyta = brown algae
  • 15. Red Algae
  • 16. Volvox – A Colonial Green Algae
  • 17. Spirogyra Conjugation
  • 18. Kelp – A Brown Algae
  • 19. Protozoans
    • Animal-like protists
      • Are heterotrophs
      • Can move
    • Classified by their means of movement
    • Four diverse groups:
      • Sarcodinians
      • Zooflagellates
      • Ciliaphorans
      • Sporozoans
  • 20. Sarcodinians
    • Protozoans that move by extending lobes of cytoplasm
      • Pseudopods = false feet
    • Example: amoeba
    • Some have hard shells of calcium carbonate or silica
      • Extend pseudopods through holes in their shells
    • Examples: foraminferans & radiolarians
  • 21. The Amoeba
  • 22. Radiolarian
  • 23. Heliozoan
  • 24. Zooflagellates
    • Protozoans that move by means of a flagella
    • Many are free-living freshwater or marine organisms
    • Many live in symbiotic relationships with other organisms
      • Example: Trichonympha live in the guts of termites and digest cellulose
    • Some are parasites that cause disease
      • Example: Trypanosoma causes African sleeping sickness
  • 25. Trypanosomes
  • 26. Trichomona
  • 27. Ciliaphorans
    • Protozoans covered with hair like projections, cilia, used to move
    • The largest and most diverse group
    • Examples:
      • Paramecium
      • Stentor
  • 28. The Paramecium
  • 29. Sporozoans
    • Have no structures for movement
    • Live as parasites on other animals
      • Spore-forming parasitic protozoans
    • Have complex life cycles that include both sexual and asexual phases
    • Some cause human diseases
      • Example: plasmodium causes malarial carried by mosquitos
  • 30. Fungus-like Protists
    • Live in damp, watery places
    • Decomposers
    • Extract nutrients from dead organisms
    • Three groups:
      • Plasmodial slime molds
      • Cellular slime molds
      • Water molds
  • 31. Plasmodial Slime Molds
    • Have different forms at different stages in their life cycle
    • Plasmodium = feeding stage
    • Forms a fruiting body that produces spores
    • Spores unite to form amoeboid zygote  the second stage
    • Mitosis of the zygote regenerates the plasmodium
  • 32. Slime Mold
  • 33. Cellular Slime Molds
    • Live in fresh water, damp soil, or decomposing plant material
    • Also alternate between an amoeboid form and a spore-producing fruiting body
    • Amoeboid stage is the feeding stage
      • Reverse of plasmodial slime molds
    • Amoeboid stage can produce a pseudoplasmodium
      • “ Pseudo” because the individual cells are still independent
    • Pseudoplasmodium produces fruiting bodies
    • Fruiting bodies produce spores
  • 34. Water Molds
    • Used to be classified as fungi
      • Fungi have cell walls that contain chitin
      • Water molds have cell wall of cellulose
      • Water molds produce spores with flagella
      • Fungi produce spores without flagella
    • Are decomposers or parasites
    • Includes water molds, white rusts, downy mildews
      • Potato blight
  • 35. Powdery Mildew