Ch 28

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Ch 28

  1. 1. 1. List the characteristics of protists. They are the earliest eukaryotes  showed up a billion years before the others Age  2.1 billion years There are 60,000 living species Exist as unicellular, colonial, and multicellular Aerobic, cilia & flagella, asexual or sexual Bottom line: a VERY diverse group 
  2. 2. 2. Explain why some biologists prefer to usethe term undulipodia for eukaryotic flagellaand cilia. Because they appear to “undulate” or wave while acting like feet or “podia” 
  3. 3. 3. Briefly summarize and compare the two majormodels of eukaryotic origins, the autogenoushypothesis and the endosymbiotic hypothesis.• Specialization of the plasma membrane invagination  gave rise to the nuclear envelope, the ER, the Golgi apparatus, etc…3. Endosymbiotic associations may have resulted in organelles  mitochondria, chloroplasts, etc… 
  4. 4. 4. Provide three major lines of evidence forthe endosymbiotic hypothesis. Similarities between organelles and prokaryotes Molecular systematics lends support  rRNA of chloroplasts is more similar in base sequence to RNA from certain eubacteria than rRNA in eukaryotic cytoplasm 9 + 2 flagella and cilia are analogous to prokaryotes 
  5. 5. 5. Explain why modern biologists recommendexpanding the original boundaries of theKingdom Protista. Observation that the Kingdom Protista is polyphyletic Current research groups protists into FIVE candidate Kingdoms 
  6. 6. 6. Explain what is meant by the statementthat the Kingdom Protista is a polyphyleticgroup. Polyphyletic = ancestry from several possible sources or directions Example: Protists are  animal-like plant-like fungus-like 
  7. 7. 7. List five candidate kingdoms of protistsand describe a major feature of each. Archaezoa  lack mitochondria Euglenozoa  are both autotrophic and heterotrophic flagellates Alveolata  have subsurface cavities (alveoli) Stramenopila  diatoms, golden brown algae, and water molds Rhodophyta  red algae; lack flagella 
  8. 8. 8. Describe amoeboid movement. Amoebas move in a characteristic motion use “pseudopodia”  form as cellular extensions and function in feeding and movement The cytoskeleton of microtubules and microfilaments functions in this amoeboid movement 
  9. 9. 9. Outline the life cycle of Plasmodium. It is the protist that causes malaria The Anopheles mosquitos serve as the intermediate host and humans are the final host The Plasmodium spends most of its life in blood or liver cells 
  10. 10. 10. Indicate the organism that causesAfrican sleeping sickness and explain how itspread and why it is difficult to control. It is a species of Trypanosoma that causes the disease and are spread by the bite of the tsetse fly It belongs in the candidate Kingdom Euglenozoa, in the group Kinetoplastids 
  11. 11. 11. Describe the function of contractilevacuoles in freshwater climates. Contractile vacuoles allow freshwater protists to: 1. Maintain water balance and homeostasis 2. Expel accumulated water from osmosis 3. Sometimes helps propel protists 
  12. 12. 12. Distinguish between macronuclei andmicronuclei. Macronuclei  large, over 50 copies of genome - controls everyday functions of the cell by synthesizing RNA - necessary for asexual reproduction during binary fission Micronuclei  small, about 1 – 80 of these - no function in growth, maintenance, or asexual reproduction - functions only in conjugation (sexual genetic variation) 
  13. 13. 13. Using diagrams, describe conjugation inParamecium caudatum. Page 530 in your book• Two paramecium have diploid micronuclei which go through meiosis to create haploid micronuclei Through syngamy, the two paramecium exchange a couple haploid micronuclei, and these fuse to become a new, varied, diploid micronucleus The new diploid micronuclei may also then follow the cycle and exchange with another paramecium throughout it’s life cycle 
  14. 14. 14. Explain how accessory pigments can beused to classify algae and determinephylogenetic relationships among divisions. Diatoms  brown plastids cause brown/yellow color Golden algae  yellow and brown carotenoids and xanthophyll Brown algae  chlorophyll a, c and the carotenoid fucoxanthin Red algae  chlorophyll a, carotenoids, phycobilins, and chlorophyll d - color is due to accessory pigment phycoerythrin 
  15. 15. 15. In a chart, distinguish among the followingalgal groups based on their pigments, cell wallcomponents, storage products, reproduction,number and position of flagella, and habitat:a. Dinoflagellata b. Bacillariophytac. Chrysophyta d. Phaeophyta
  16. 16. 16. Describe three possible evolutionarytrends that led to multicellularity in theChlorophyta.• Formation of colonies of individual cells ex: Volvox3. Repeated division of nuclei with no cytoplasmic division (mitosis without cytokinesis ex: Caulerpa5. Formation of true multicellular forms ex: Ulva 
  17. 17. Life Cycle overview Sporophyte  generally the adult form of an organism; exists as a diploid (2n); makes spores (ex: humans) Gametophyte  generally an intermediate step before fertilization; exists as a haploid (n); makes gametes (ex: sperm & eggs) 
  18. 18. 17. Outline the life cycles of Chlamydomonas,Ulva, and Laminaria and indicate whether thestages are haploid or diploid. Chlamydomonas  at maturity it is a single haploid cell - asexual at first, then sexual only if stressed, creating a diploid zygote2. Ulva  diploid sporophyte and haploid gametophyte3. Laminaria  sporophyte (2n) with sporangia makes zoospores (n) which make gametes (n) and then fertilization to get diploid sporophyte again 
  19. 19. 18. Distinguish between isogamy and oogamy;sporophyte and gametophyte; and isomorphicand heteromorphic generations. Isogamy  when gametes are morphologically indistinguishable Oogamy  flagellated sperm fertilize the nonmotile egg Sporophyte  2n (diploid) generation Gametophyte  n (haploid) generation Isomorphic  gametophytes and sporophytes look alike Heteromorphic  gametophytes and sporophytes are structurally different 
  20. 20. 19. Compare the life cycles of plasmodial andcellular slime molds and describe the majordifferences between them. Plasmodial Slime Mold Cellular Slime Mold Multinucleated mass Solitary haploid cells Diploid nuclei Cells will aggregate When stressed will when food supply is form sexual low reproductive Fruiting bodies structures called (sporangia) function in sporangia  asexual reproduction 
  21. 21. 20. Provide evidence that the oomycetes arenot closely related to true fungi. Have coenocytic (multinucleated) hyphae (branching filaments) that are analogous to fungal hyphae Cell walls are made of cellulose rather than the chitin in true fungi Have biflagellated cells  fungi lack flagellated cells 
  22. 22. 21. Give examples of oomycetes and describetheir economic importance. Water molds  grow on injured tissue but also will grow on the skin and gills of fish White rusts Downy mildews - both of these are parasitic on terrestrial plants – act as pathogens 
  23. 23. 22. Explain the most widely acceptedhypothesis for the evolution ofmulticellularity. Multicellularity arose from unicellular ancestors as colonies or loose aggregates of interconnected cells This involved cellular specialization and division of labor among the cells The End 

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