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  1. 1. © 2010 Pearson Education, Inc.  Welcome to Chapter 15
  2. 2. © 2010 Pearson Education, Inc. MAJOR EPISODES IN THE HISTORY OF LIFE • Earth was formed about 4.6 billion years ago. • Prokaryotes – Evolved by 3.5 billion years ago – Continue in great abundance today
  3. 3. © 2010 Pearson Education, Inc. • Single-celled eukaryotes first evolved about 2.1 billion years ago. • Multicellular eukaryotes first evolved at least 1.2 billion years ago.
  4. 4. Paleozoic Mesozoic Cenozoic Bacteria Archaea Plants Fungi Animals ProkaryotesEukaryotes Protists Oldest eukaryotic fossils Origin of multicellular organisms Oldest animal fossils Plants and symbiotic fungi colonize land Extinction of dinosaurs First humans Millions of years ago Cambrian explosion 2,000 1,500 1,000 500 0 Figure 15.1b
  5. 5. © 2010 Pearson Education, Inc. • All the major phyla of animals evolved by the end of the Cambrian explosion, which began about 540 million years ago and lasted about 10 million years. • Plants and fungi – First colonized land about 500 million years – Were followed by amphibians that evolved from fish
  6. 6. © 2010 Pearson Education, Inc. • We can use a clock analogy to look at the major events in the history of life on Earth
  7. 7. Humans Origin of solar system and Earth 1 4 0 2 3 Present Anim als Coloniz of land ation Multi eukar cellular yotes Sing eukar cel yotes le- led Atmo oxy spheric gen Bil arsons of ago ye li karyotes Pro Figure 15.2
  8. 8. © 2010 Pearson Education, Inc. THE ORIGIN OF LIFE • We may never know for sure how life on Earth began.
  9. 9. © 2010 Pearson Education, Inc. Resolving the Biogenesis Paradox • All life today arises by the reproduction of preexisting life, or biogenesis. • If this is true, how could the first organisms arise? • From the time of the ancient Greeks until well into the 19th century, it was commonly believed that life regularly arises from nonliving matter, an idea called spontaneous generation.
  10. 10. © 2010 Pearson Education, Inc. • Today, most biologists think it is possible that life on early Earth produced simple cells by chemical and physical processes.
  11. 11. © 2010 Pearson Education, Inc. Stage 2: Abiotic Synthesis of Polymers • Researchers have brought about the polymerization of monomers to form polymers, such as proteins and nucleic acids, by dripping solutions of organic monomers onto – Hot sand – Clay – Rock
  12. 12. © 2010 Pearson Education, Inc. From Chemical Evolution to Darwinian Evolution • Over millions of years – Natural selection favored the most efficient cells – The first prokaryotic cells evolved
  13. 13. © 2010 Pearson Education, Inc. PROKARYOTES • Prokaryotes lived and evolved all alone on Earth for 2 billion years before eukaryotes evolved.
  14. 14. © 2010 Pearson Education, Inc. They’re Everywhere! • Prokaryotes – Are found wherever there is life – Far outnumber eukaryotes – Can cause disease – Can be beneficial
  15. 15. © 2010 Pearson Education, Inc. • Prokaryotes live deep within the Earth and in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote to survive.
  16. 16. © 2010 Pearson Education, Inc. • Compared to eukaryotes, prokaryotes are – Much more abundant – Typically much smaller
  17. 17. © 2010 Pearson Education, Inc. • Prokaryotes – Are ecologically significant, recycling carbon and other vital chemical elements back and forth between organic matter, the soil, and atmosphere – Cause about half of all human diseases – Are more typically benign or beneficial
  18. 18. © 2010 Pearson Education, Inc. The Structure and Function of Prokaryotes • Prokaryotic cells – Lack true nuclei – Lack other membrane-enclosed organelles – Have cell walls exterior to their plasma membranes
  19. 19. Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) ColorizedTEM Figure 4.4
  20. 20. © 2010 Pearson Education, Inc. • Prokaryotes come in several shapes: – Spherical (cocci) – Rod-shaped (bacilli) – Spiral Procaryotic Forms
  21. 21. ColorizedSEM Figure 15.8a
  22. 22. ColorizedSEM Figure 15.8b
  23. 23. ColorizedTEM Figure 15.8c
  24. 24. © 2010 Pearson Education, Inc. • Most prokaryotes are – Unicellular – Very small • Some prokaryotes – Form true colonies – Show specialization of cells – Are very large Video: Cyanobacteria (Oscillatoria)
  25. 25. © 2010 Pearson Education, Inc. • About half of all prokaryotes are mobile, using flagella. • Many have one or more flagella that propel the cells away from unfavorable places or toward more favorable places, such as nutrient-rich locales. Video: Prokaryotic Flagella (Salmonella typhimurium) (random)
  26. 26. Plasma membrane Cell wall Rotary movement of each flagellum Flagellum ColorizedTEM Figure 15.10
  27. 27. © 2010 Pearson Education, Inc. • Most prokaryotes can reproduce by binary fission and at very high rates if conditions are favorable. • Some prokaryotes – Form endospores, thick-coated, protective cells that are produced within the cells when they are exposed to unfavorable conditions – Can survive very harsh conditions for extended periods, even centuries Procaryotic Reproduction
  28. 28. Endospore ColorizedSEM Figure 15.11
  29. 29. © 2010 Pearson Education, Inc. Procaryotic Nutrition • Prokaryotes exhibit four major modes of nutrition. – Phototrophs obtain energy from light. – Chemotrophs obtain energy from environmental chemicals. – Species that obtain carbon from carbon dioxide (CO2) are autotrophs. – Species that obtain carbon from at least one organic nutrient—the sugar glucose, for instance—are called heterotrophs.
  30. 30. © 2010 Pearson Education, Inc. • We can group all organisms according to the four major modes of nutrition if we combine the – Energy source (phototroph versus chemotroph) and – Carbon source (autotroph versus heterotroph)
  31. 31. MODES OF NUTRITION Light Chemical ChemoautotrophsPhotoautotrophs Photoheterotrophs Chemoheterotrophs Energy source Elodea, an aquatic plant Rhodopseudomonas Little Owl (Athene noctua) Bacteria from a hot spring Organiccompounds Carbonsource CO2 ColorizedTEM ColorizedTEM Figure 15.12
  32. 32. The Two Main Branches of Prokaryotic Evolution: Bacteria and Archaea • By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: – Bacteria – Archaea (more closely related to eukaryotes) – clip © 2010 Pearson Education, Inc.
  33. 33. © 2010 Pearson Education, Inc. • Some archaea are “extremophiles.” – Halophiles thrive in salty environments. – Thermophiles inhabit very hot water.
  34. 34. (a) Salt-loving archaea (b) Heat-loving archaea Figure 15.13
  35. 35. (a) Salt-loving archaea Figure 15.13a
  36. 36. (b) Heat-loving archaea Figure 15.13b
  37. 37. © 2010 Pearson Education, Inc. Bacteria and Humans • Bacteria interact with humans in many ways.
  38. 38. © 2010 Pearson Education, Inc. Bacteria That Cause Disease • Bacteria and other organisms that cause disease are called pathogens. • Most pathogenic bacteria produce poisons. – Exotoxins are poisonous proteins secreted by bacterial cells. – Endotoxins are not cell secretions but instead chemical components of the outer membrane of certain bacteria.
  39. 39. Haemophilus influenzae Cells of nasal lining ColorizedSEM Figure 15.14
  40. 40. © 2010 Pearson Education, Inc. • The best defenses against bacterial disease are – Sanitation – Antibiotics – Education
  41. 41. © 2010 Pearson Education, Inc. • Lyme disease is – Caused by bacteria carried by ticks – Treated with antibiotics
  42. 42. “Bull’s-eye” rash Tick that carries the Lyme disease bacterium Spirochete that causes Lyme disease SEM Figure 15.15
  43. 43. Tick that carries the Lyme disease bacterium Figure 15.15b
  44. 44. Figure 15.15c
  45. 45. Spirochete that causes Lyme disease Figure 15.15d
  46. 46. © 2010 Pearson Education, Inc. Bioterrorism • Humans have a long and ugly history of using organisms as weapons. – During the Middle Ages, armies hurled the bodies of plague victims into enemy ranks. – Early conquerors, settlers, and warring armies in South and North America gave native peoples items purposely contaminated with infectious bacteria. – In 1984, members of a cult in Oregon contaminated restaurant salad bars with Salmonella bacteria. – In the fall of 2001, five Americans died from the disease anthrax in a presumed terrorist attack.
  47. 47. Figure 15.16
  48. 48. © 2010 Pearson Education, Inc. The Ecological Impact of Prokaryotes • Pathogenic bacteria are in the minority among prokaryotes. • Far more common are species that are essential to our well-being, either directly or indirectly.
  49. 49. © 2010 Pearson Education, Inc. Prokaryotes and Chemical Recycling • Prokaryotes play essential roles in – Chemical cycles in the environment – The breakdown of organic wastes and dead organisms
  50. 50. © 2010 Pearson Education, Inc. Prokaryotes and Bioremediation • Bioremediation is the use of organisms to remove pollutants from – Water – Air – Soil • A familiar example is the use of prokaryotic decomposers in sewage treatment.
  51. 51. © 2010 Pearson Education, Inc. • Certain bacteria – Can decompose petroleum – Are useful in cleaning up oil spills
  52. 52. Figure 15.18
  53. 53. © 2010 Pearson Education, Inc. PROTISTS • Protists – Are eukaryotic – Evolved from prokaryotic ancestors
  54. 54. © 2010 Pearson Education, Inc. The Diversity of Protists • Protists can be – Unicellular – Multicellular • More than any other group, protists vary in – Structure – Function
  55. 55. © 2010 Pearson Education, Inc. • Protists are not one distinct group but instead represent all the eukaryotes that are not plants, animals, or fungi.
  56. 56. © 2010 Pearson Education, Inc. • The classification of protists remains a work in progress. • The four major categories of protists, grouped by lifestyle, are – Protozoans – Slime molds – Unicellular algae – Seaweeds
  57. 57. © 2010 Pearson Education, Inc. Protozoans • Protists that live primarily by ingesting food are called protozoans. • Protozoans with flagella are called flagellates and are typically free-living, but sometimes are parasites. Video: Euglena Motion
  58. 58. A flagellate: Giardia ColorizedSEM Figure 15.21a
  59. 59. Another flagellate: trypanosomes ColorizedSEM Figure 15.21b
  60. 60. © 2010 Pearson Education, Inc. • Amoebas are characterized by – Great flexibility in their body shape – The absence of permanent organelles for locomotion • Most species move and feed by means of pseudopodia (singular, pseudopodium), temporary extensions of the cell. Video: Amoeba Pseudopodia Video: Amoeba
  61. 61. An amoeba LM Figure 15.21c
  62. 62. © 2010 Pearson Education, Inc. • Apicomplexans are – Named for a structure at their apex (tip) that is specialized for penetrating host cells and tissues – All parasitic, such as Plasmodium, which causes malaria
  63. 63. An apicomplexan TEM Figure 15.21e
  64. 64. © 2010 Pearson Education, Inc. • Ciliates – Are mostly free-living (nonparasitic), such as the freshwater ciliate Paramecium – Use structures called cilia to move and feed Video: Paramecium Vacuole Video: Paramecium Cilia Video: Vorticella Habitat Video: Vorticella Detail Video: Vorticella Cilia
  65. 65. A ciliate LM Figure 15.21f
  66. 66. © 2010 Pearson Education, Inc. Slime Molds • The two main groups of these protists are – Plasmodial slime molds – Cellular slime molds
  67. 67. © 2010 Pearson Education, Inc. • Plasmodial slime molds – Can be large – Are decomposers on forest floors Video: Plasmodial Slime Mold Video: Plasmodial Slime Mold Streaming
  68. 68. © 2010 Pearson Education, Inc. • Cellular slime molds have an interesting and complex life cycle that changes between a
  69. 69. © 2010 Pearson Education, Inc. Unicellular and Colonial Algae • Algae are – Photosynthetic protists – Found in plankton, the communities of mostly microscopic organisms that drift or swim weakly in aquatic environments
  70. 70. © 2010 Pearson Education, Inc. • Unicellular algae include – Diatoms, which have glassy cell walls containing silica – Dinoflagellates, with two beating flagella and external plates made of cellulose
  71. 71. (a) A dinoflagellate, with its wall of protective plates SEM Figure 15.24a
  72. 72. b) A sample of diverse diatoms, which have glossy walls LM Figure 15.24b
  73. 73. © 2010 Pearson Education, Inc. • Green algae are – Unicellular – Sometimes flagellated, such as Chlamydomonas – Colonial, sometimes forming a hollow ball of flagellated cells, as seen in Volvox Video: Volvox Flagella Video: Volvox Daughter Video: Volvox Colony Video: Chlamydomonas
  74. 74. (d) Volvox, a colonial green alga LM Figure 15.24d
  75. 75. (a) A dinoflagellate, with its wall of protective plates (c) Chlamydomonas, a unicellular green alga with a pair of flagella (b) A sample of diverse diatoms, which have glossy walls (d) Volvox, a colonial green alga ColorizedSEMSEM LMLM Figure 15.24
  76. 76. © 2010 Pearson Education, Inc. Seaweeds • Seaweeds – Are large, multicellular marine algae – Grow on or near rocky shores – Are often edible
  77. 77. © 2010 Pearson Education, Inc. • Seaweeds are classified into three different groups, based partly on the types of pigments present in their chloroplasts: – Green algae – Red algae – Brown algae (including kelp)
  78. 78. Green algae Red algae Brown algae Figure 15.25
  79. 79. Green algae Figure 15.25a
  80. 80. Red algae Figure 15.25b
  81. 81. Brown algae Figure 15.25c
  82. 82. Figure 15.UN01 Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals
  83. 83. Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals Figure 15.UN02
  84. 84. Major episode Millions of years ago All major animal phyla established Plants and fungi colonize land Origin of Earth First multicellular organisms Oldest eukaryotic fossils Accumulation of O2 in atmosphere Oldest prokaryotic fossils 500 530 1,200 1,800 2,400 3,500 4,600 Figure 15.UN03
  85. 85. Inorganic compounds Abiotic synthesis of organic monomers Abiotic synthesis of polymers Formation of pre-cells Self-replicating molecules Membrane-enclosed compartment Complementary chain Polymer Organic monomers Figure 15.UN04
  86. 86. Spherical Rod-shaped Spiral Figure 15.UN05
  87. 87. Nutritional Mode Energy Source Carbon Source Photoautotroph Chemoautotroph Photoheterotroph Chemoheterotroph Sunlight Inorganic chemicals Sunlight Organic compounds CO2 Organic compounds Figure 15.UN06
  88. 88. Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals Figure 15.UN07
  89. 89. Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals Figure 15.UN08

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