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17 Lecture Ppt

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 17 Evolution of Protists
  2. 2. Protists May Represent the Oldest Eukaryotic Cells 17-
  3. 3. 17.1 Eukaryotic organelles probably arose by endosymbiosis <ul><li>Protists (kingdom Protista) are eukaryotes </li></ul><ul><ul><li>Endosymbiotic theory - at least mitochondria and chloroplasts are derived from independent prokaryotic cells </li></ul></ul>17-
  4. 4. Figure 17.1 Origin of mitochondria (above) and chloroplasts (below) 17-
  5. 5. 17.2 Protists are a diverse group <ul><li>Protists vary in size from microscopic to macroscopic exceeding 200 m in length </li></ul><ul><ul><li>Most protists are unicellular, but they have attained a high level of complexity </li></ul></ul><ul><li>Asexual reproduction by mitosis is the norm in protists </li></ul><ul><ul><li>Sexual reproduction generally occurs only in a hostile environment </li></ul></ul><ul><li>They are of enormous ecological importance </li></ul><ul><ul><li>They are a major component of plankton </li></ul></ul><ul><ul><ul><li>Organisms suspended in the water and are food for animals </li></ul></ul></ul><ul><ul><li>Protists have symbiotic relationships from parasitism to mutualism </li></ul></ul>17-
  6. 6. Figure 17.2 Protist diversity 17-
  7. 7. APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES 17.3 How can the protists be classified? <ul><li>Lumping all the single-celled eukaryotes (protists) into a single kingdom is artificial </li></ul><ul><ul><li>Does not represent evolutionary history </li></ul></ul>17-
  8. 8. Figure 17.3 Proposed evolutionary tree of protists (blue branches) based on DNA and RNA sequencing 17-
  9. 9. Protozoans Are Heterotrophic Protists with Various Means of Locomotion 17-
  10. 10. 17.4 Protozoans called flagellates move by flagella <ul><li>Zooflagellates - thousands of species of mostly unicellular, heterotrophic protozoans that move with a flagellum </li></ul><ul><ul><li>Many zooflagellates are symbiotic and some are parasitic </li></ul></ul><ul><li>Euglenoids include about 1,000 species of small (10–500 μm) freshwater unicellular organisms </li></ul><ul><ul><li>One-third of all genera have chloroplasts; the rest do not </li></ul></ul><ul><ul><li>Those that lack chloroplasts ingest or absorb their food </li></ul></ul><ul><ul><li>Some do both </li></ul></ul><ul><ul><ul><li>Euglena deces , an inhabitant of freshwater ditches and ponds can undergo photosynthesis as well as to ingest food </li></ul></ul></ul>17-
  11. 11. Figure 17.4 Euglena , a flagellate 17-
  12. 12. 17.5 Protozoans called amoeboids move by pseudopods <ul><li>Pseudopods - extensions that form when cytoplasm streams in a particular direction </li></ul><ul><ul><li>May be zooplankton, microscopic suspended organisms that feed on other organisms </li></ul></ul><ul><li>Feed by phagocytosis, surrounding prey with pseudopods and digesting it in a food vacuole </li></ul><ul><li>Foraminiferans and Radiolarians have shells called tests </li></ul><ul><ul><li>Intriguing and beautiful </li></ul></ul><ul><ul><li>In foraminiferans the test is often multichambered </li></ul></ul><ul><ul><li>Deposits of foraminiferans formed the White Cliffs of Dover </li></ul></ul>17-
  13. 13. Figure 17.5A Amoeba proteus , an amoeboid 17-
  14. 14. Figure 17.5B Foraminiferans, such as Globigerina, built the White Cliffs of Dover, England 17-
  15. 15. Figure 17.5C Radiolarian tests 17-
  16. 16. 17.6 Protozoans called ciliates move by cilia <ul><li>Ciliates - approximately 8,000 species of unicellular protists </li></ul><ul><ul><li>Range from 10 to 3,000 μm in size </li></ul></ul><ul><li>The most structurally complex and specialized of all protozoans </li></ul><ul><ul><li>The majority are free-living </li></ul></ul><ul><ul><ul><li>Several parasitic, sessile, and colonial forms exist </li></ul></ul></ul><ul><li>When a paramecium feeds, food particles are swept down a gullet into food vacuoles </li></ul><ul><li>Asexual reproduction </li></ul><ul><ul><li>Ciliates divide by transverse binary fission </li></ul></ul><ul><li>Sexual reproduction involves conjugation </li></ul>17-
  17. 17. Figure 17.6A Paramecium , a ciliate 17-
  18. 18. Figure 17.6B During conjugation, two paramecia first unite at oral areas 17-
  19. 19. Figure 17.6C Stentor , a ciliate 17-
  20. 20. 17.7 Protozoans called sporozoans are not motile <ul><li>Sporozoans - nearly 3,900 species </li></ul><ul><ul><li>nonmotile, parasitic, spore-forming </li></ul></ul><ul><ul><ul><li>Many sporozoans have multiple hosts </li></ul></ul></ul><ul><li>One million people die each year from malaria </li></ul><ul><ul><li>Widespread disease caused by four types of sporozoan parasites in the genus Plasmodium </li></ul></ul>17-
  21. 21. Figure 17.7 Life cycle of Plasmodium vivax , the cause of one type of malaria 17-
  22. 22. Some Protists Have Moldlike Characteristics 17-
  23. 23. 17.8 The diversity of protists includes slime molds and water molds <ul><li>The Plasmodial Slime Molds </li></ul><ul><ul><li>Exist as a plasmodium, a diploid, multinucleated, cytoplasmic mass </li></ul></ul><ul><ul><ul><li>Enveloped by a slimy sheath creeping along, phagocytizing decaying plant material </li></ul></ul></ul><ul><ul><li>During droughts, plasmodium develops many sporangia , spore producing reproductive structures </li></ul></ul><ul><ul><ul><li>An aggregate of sporangia is called a fruiting body </li></ul></ul></ul>17-
  24. 24. Cellular Slime Molds <ul><li>Exist as individual amoeboid cells and are too small to be seen </li></ul><ul><ul><li>Common in soil, feeding on bacteria and yeasts </li></ul></ul><ul><li>As the food supply runs out cells release a chemical that causes them to aggregate into a pseudoplasmodium </li></ul><ul><ul><li>Eventually gives rise to a fruiting body </li></ul></ul>17-
  25. 25. Figure 17.8 Life cycle of plasmodial slime molds 17-
  26. 26. Water Molds <ul><li>Water Molds </li></ul><ul><ul><li>Usually live in water, where they form furry growths when they parasitize fishes or insects and decompose remains </li></ul></ul><ul><ul><li>Water molds have a filamentous body as do fungi, but their cell walls are largely composed of cellulose </li></ul></ul>17-
  27. 27. 17-
  28. 28. Algae Are Photosynthetic Protists of Environmental Importance 17-
  29. 29. 17.9 The diatoms and dinoflagellates are significant algae in the oceans <ul><li>Diatoms (approximately 11,000 species) are free-living photosynthetic cells in aquatic and marine environments </li></ul><ul><ul><li>Most numerous unicellular algae in the oceans and freshwater environments </li></ul></ul><ul><ul><li>Significant part of the phytoplankton , photosynthetic organisms suspended in the water </li></ul></ul><ul><ul><li>Serve as an important source of food and oxygen for heterotrophs </li></ul></ul><ul><li>Diatom Structure </li></ul><ul><ul><li>Often compared to a hat box </li></ul></ul><ul><ul><li>Cell wall has two halves, or valves, with the larger valve acting as a “lid” that fits over the smaller valve </li></ul></ul>17-
  30. 30. Figure 17.9A Cyclotella , a diatom. Diatoms live in “glass houses” because the outer visible valve, which fits over the smaller inner valve, contains silica 17-
  31. 31. Dinoflagellates <ul><li>Dinoflagellates (about 4,000 species) are usually bounded by protective cellulose plates impregnated with silicates </li></ul><ul><ul><li>Typically, the organism has two flagella: </li></ul></ul><ul><ul><ul><li>One in a longitudinal groove with its distal end free </li></ul></ul></ul><ul><ul><ul><li>One in a transverse groove that encircles the organism </li></ul></ul></ul><ul><ul><li>Important source of food for small animals in the ocean </li></ul></ul><ul><ul><li>Some are symbionts in the bodies of invertebrates </li></ul></ul><ul><ul><ul><li>Corals usually contain large numbers of zooxanthellae </li></ul></ul></ul><ul><ul><li>Some undergo a population explosion and cause “red tides” </li></ul></ul>17-
  32. 32. Figure 17.9B Gonyaulax , a dinoflagellate. This dinoflagellate is responsible for the poisonous “red tide” that sometimes occurs along the coasts 17-
  33. 33. 17.10 Red algae and brown algae are multicellular <ul><li>Red algae (>5,000 multicellular species) living primarily in warm seawater </li></ul><ul><ul><li>Some grow attached to rocks in the intertidal zone </li></ul></ul><ul><ul><li>Others can grow at depths exceeding 200 m </li></ul></ul><ul><ul><li>economically important </li></ul></ul><ul><ul><ul><li>Produce agar, a gelatin-like product made primarily from the algae Gelidium and Gracilaria, used commercially and in the laboratory </li></ul></ul></ul><ul><li>Brown algae (>1,500 species of seaweeds) </li></ul><ul><ul><li>Range from small forms with simple filaments to large, multicellular forms that may reach 100 m in length </li></ul></ul><ul><ul><li>Majority of brown algae, like Fucus, live in cold ocean waters </li></ul></ul><ul><li>Multicellular forms of green, red, and brown algae are called seaweeds , a common term for any large, complex alga </li></ul>17-
  34. 34. Figure 17.10A Chondrus crispus , a red alga 17-
  35. 35. Figure 17.10B Rockweed, Fucus , a brown alga 17-
  36. 36. 17.11 Green algae are ancestral to plants <ul><li>Green algae (Approximately 7,500 species) </li></ul><ul><ul><li>Not always green </li></ul></ul><ul><ul><ul><li>Some have an orange, red, or rust color </li></ul></ul></ul><ul><ul><li>Inhabit a variety of environments </li></ul></ul><ul><ul><ul><li>Oceans, freshwater, snowbanks, bark of trees, backs of turtles </li></ul></ul></ul><ul><li>Lichen-symbiotic algal relationship with fungi </li></ul><ul><li>Filaments - end-to-end chains of cells that form after cell division in only one plane </li></ul><ul><ul><li>In some algae, the filaments are branched, and in others the filaments are unbranched </li></ul></ul><ul><li>Asexual Reproduction </li></ul><ul><ul><li>Chlamydomonas produces 16 daughter cells still within the parent cell </li></ul></ul><ul><li>Sexual reproduction </li></ul><ul><ul><li>Spirogyra undergoes conjugation, temporary union, during which cells exchange genetic material </li></ul></ul>17-
  37. 37. Figure 17.11A Reproduction in Chlamydomonas , a motile green alga 17-
  38. 38. Figure 17.11B Cell anatomy and conjugation in Spirogyra , a filamentous green alga 17-
  39. 39. Figure 17.11C Volvox , a colonial green alga 17-
  40. 40. Figure 17.11D Ulva , a multicellular alga 17-
  41. 41. Figure 17.11E Chara , a stonewort 17-
  42. 42. APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES 17.12 Life cycles among the algae have many variations <ul><li>Asexual Reproduction </li></ul><ul><ul><li>When environment is favorable to growth, asexual reproduction is a frequent mode of reproduction among protists </li></ul></ul><ul><ul><ul><li>Offspring are identical to parent </li></ul></ul></ul><ul><li>Sexual Reproduction </li></ul><ul><ul><li>More likely to occur among protists when the environment is changing and is unfavorable to growth </li></ul></ul><ul><ul><ul><li>May produce individuals more likely to survive extreme environments </li></ul></ul></ul><ul><li>Haploid life cycle </li></ul><ul><ul><li>The zygote divides by meiosis to form haploid spores that develop into haploid individuals </li></ul></ul><ul><li>Alternation of generations </li></ul><ul><ul><li>Diploid sporophyte produces haploid spores </li></ul></ul><ul><ul><li>Spore develops into a haploid gametophyte that produces gametes </li></ul></ul><ul><ul><li>Gametes fuse to form a diploid zygote that develops into sporophyte </li></ul></ul><ul><li>Diploid life cycle </li></ul><ul><ul><li>Diploid individual produces haploid gametes by meiosis </li></ul></ul><ul><ul><li>Gametes fuse to form a diploid zygote </li></ul></ul>17-
  43. 43. Figure 17.12A Haploid life cycle 17-
  44. 44. <ul><li>Figure 17.12B Alternation of generations </li></ul>17-
  45. 45. Figure 17.12C Diploid life cycle 17-
  46. 46. Connecting the Concepts: Chapter 17 <ul><li>Protists we study today are not expected to include the direct ancestors to fungi, plants, and animals </li></ul><ul><ul><li>They may be related to the other eukaryotic groups by way of common ancestors that have not been discovered in the fossil record </li></ul></ul><ul><ul><li>May represent an adaptive radiation experienced by the first eukaryotic cell </li></ul></ul><ul><li>Mutualism is a powerful force that shaped the eukaryotic cell and also shapes all sorts of relationships in the living world </li></ul><ul><li>All possible forms of reproduction and nutrition are present among the protists </li></ul><ul><ul><li>Each of the other eukaryotic groups specializes in a particular type of reproduction and a particular method of acquiring needed nutrients </li></ul></ul>17-