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Chapter 15 The Evolution of Microbial Life

0. Chapter 15 The Evolution of Microbial Life. Biology and Society: Can Life Be Created in the Lab?. A research group led by Craig Venter Synthesized the entire genome of Mycoplasma genitalium , a species of bacteria found naturally in the human urinary tract

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Chapter 15 The Evolution of Microbial Life

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  1. 0 Chapter 15The Evolution of Microbial Life Laura Coronado Bio 10 Chapter 15

  2. Biology and Society: Can Life Be Created in the Lab? • A research group led by Craig Venter • Synthesized the entire genome of Mycoplasmagenitalium, a species of bacteria found naturally in the human urinary tract • Transplanted the complete genome of one species of Mycoplasmabacteria into another • Hopes to create an artificial genome & transplant it into a genome-free host cell • An artificial organism that could be completely controlled might • Clean up toxic wastes • Generate biofuels • Be unable to survive outside rigidly controlled conditions Laura Coronado Bio 10 Chapter 15

  3. MAJOR EPISODES IN THE HISTORY OF LIFE • Earth was formed about 4.6 billion years ago. • Prokaryotes • Evolved by 3.5 billion years ago • Began oxygen production about 2.7 billion years ago • Lived alone for almost 2 billion years • Continue in great abundance today • Single-celled eukaryotes first evolved about 2.1 billion years ago. • Multicellular eukaryotes first evolved at least 1.2 billion years ago. Laura Coronado Bio 10 Chapter 15

  4. Precambrian Common ancestor toall present-day life Atmospheric oxygen begins to appear due to photosynthetic prokaryotes Origin ofEarth Earth cool enough for crust to solidify Oldest prokaryotic fossils 4,500 4,000 3,500 3,000 2,500 Millions of years ago Laura Coronado Bio 10 Chapter 15 Figure 15.1a

  5. Paleozoic Mesozoic Cenozoic Bacteria Prokaryotes Archaea Protists Eukaryotes Plants Fungi Animals Cambrian explosion Oldest eukaryotic fossils Origin of multicellular organisms Oldest animal fossils Plants and symbiotic fungi colonize land Extinction of dinosaurs First humans 2,000 1,500 1,000 500 0 Millions of years ago Laura Coronado Bio 10 Chapter 15 Figure 15.1b

  6. Major episode Millions of years ago Plants and fungi colonize land 500 530 All major animal phyla established First multicellular organisms 1,200 1,800 Oldest eukaryotic fossils 2,400 Accumulation of O2 in atmosphere Oldest prokaryotic fossils 3,500 Origin of Earth 4,600 Laura Coronado Bio 10 Chapter 15 Figure 15.UN03

  7. MAJOR EPISODES IN THE HISTORY OF LIFE • 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 • What if we use a clock analogy to tick down all of the major events in the history of life on Earth? Laura Coronado Bio 10 Chapter 15

  8. of land ation Coloniz yotes eukar cellular sent Pre Multi otes yotes kary Bil ago eukar li ars ons Pro ye of led cel le- Atmo Sing sphe ric gen oxy Humans Animals Origin of solar system and Earth 0 4 1 2 3 Laura Coronado Bio 10 Chapter 15 Figure 15.2

  9. 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. • Today, most biologists think it is possible that life on early Earth produced simple cells by chemical and physical processes. Laura Coronado Bio 10 Chapter 15

  10. Laura Coronado Bio 10 Chapter 15 Figure 15.3

  11. A Four-Stage Hypothesis for the Origin of Life • According to one hypothesis, the first organisms were products of chemical evolution in four stages. • Stage 1: Abiotic Synthesis of Organic Monomers • The first stage in the origin of life has been the most extensively studied by scientists in the laboratory. Laura Coronado Bio 10 Chapter 15

  12. The Process of Science: Can BiologicalMonomers Form Spontaneously? • Observation: Modern biological macromolecules are all composed of elements that were present in abundance on the early Earth. • Question: Could biological molecules arise spontaneously under conditions like those on the early Earth? • Hypothesis: A closed system designed in the laboratory to simulate early Earth conditions could produce biologically important organic molecules from inorganic ingredients. • Prediction: Organic molecules would form and accumulate. Laura Coronado Bio 10 Chapter 15

  13. The Process of Science: Can BiologicalMonomers Form Spontaneously? • Experiment: An apparatus was built to mimic the early Earth atmosphere and included • Hydrogen gas (H2), methane (CH4), ammonia (NH3), and water vapor (H2O) • Sparks were discharged into the chamber to mimic the prevalent lightning of the early Earth • A condenser to cool the atmosphere, causing water and dissolved compounds to “rain” into the miniature “sea” Laura Coronado Bio 10 Chapter 15

  14. “Atmosphere” CH4 Water vapor H2 NH3 Electrode Condenser Cold water Cooled water containing organic molecules H2O Stanley Miller re-creating his 1953 experiment “Sea” Sample for chemical analysis Miller and Urey’s experiment Laura Coronado Bio 10 Chapter 15 Figure 15.4

  15. The Process of Science: Can BiologicalMonomers Form Spontaneously? • Results: After the apparatus had run for a week, an abundance of organic molecules essential for life had collected in the “sea,” including amino acids, the monomers of proteins. • Since Miller and Urey’s experiments, laboratory analogues of the primeval Earth have produced • All 20 amino acids • Several sugars Laura Coronado Bio 10 Chapter 15

  16. 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 Laura Coronado Bio 10 Chapter 15

  17. Stage 3: Formation of Pre-Cells • A key step in the origin of life was the isolation of a collection of abiotically created molecules within a membrane. • Laboratory experiments demonstrate that pre-cells could have formed spontaneously from abiotically produced organic compounds. • Such pre-cells produced in the laboratory display some lifelike properties. They: • Have a selectively permeable surface • Can grow by absorbing molecules from their surroundings • Swell or shrink when placed in solutions of different salt concentrations Laura Coronado Bio 10 Chapter 15

  18. Inorganic compounds Abiotic synthesis of organic monomers Organic monomers Abiotic synthesis of polymers Polymer Formation of pre-cells Membrane-enclosed compartment Self-replicating molecules Complementary chain Laura Coronado Bio 10 Chapter 15 Figure 15.UN04

  19. Stage 4: Origin of Self-Replicating Molecules • Life is defined partly by the process of inheritance, which is based on self-replicating molecules. • One hypothesis is that the first genes were short strands of RNA that replicated themselves without the assistance of proteins, perhaps using RNAs that can act as enzymes, called ribozymes. Laura Coronado Bio 10 Chapter 15

  20. Original “gene” Complementary RNA chain Laura Coronado Bio 10 Chapter 15 Figure 15.5

  21. From Chemical Evolution to Darwinian Evolution • Over millions of years • Natural selection favored the most efficient pre-cells • The first prokaryotic cells evolved • Prokaryotes lived and evolved all alone on Earth for 2 billion years before eukaryotes evolved. • Are found wherever there is life • Far outnumber eukaryotes • Can cause disease • Can be beneficial • 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. Laura Coronado Bio 10 Chapter 15

  22. Laura Coronado Bio 10 Chapter 15 Figure 15.6

  23. Prokaryotes • Compared to eukaryotes, prokaryotes are • Much more abundant • Typically much smaller • 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 Laura Coronado Bio 10 Chapter 15

  24. Colorized SEM Laura Coronado Bio 10 Chapter 15 Figure 15.7

  25. The Structure and Function of Prokaryotes • Prokaryotic cells • Lack true nuclei • Lack other membrane-enclosed organelles • Have cell walls exterior to their plasma membranes • Prokaryotes come in several shapes: • Spherical (cocci) • Rod-shaped (bacilli) • Spiral • Most prokaryotes are unicellular & very small Laura Coronado Bio 10 Chapter 15

  26. Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM Laura Coronado Bio 10 Chapter 15 Figure 4.4

  27. Ribosomes Centriole Not in most plant cells Lysosome Cytoskeleton Flagellum Plasma membrane Nucleus Mitochondrion Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum (ER) Golgi apparatus Idealized animal cell Cytoskeleton Central vacuole Mitochondrion Nucleus Not in animal cells Cell wall Rough endoplasmic reticulum (ER) Chloroplast Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Channels between cells Idealized plant cell Golgi apparatus Laura Coronado Bio 10 Chapter 15 Figure 4.5

  28. SHAPES OF PROKARYOTIC CELLS Spherical (cocci) Rod-shaped (bacilli) Spiral Colorized SEM Colorized SEM Colorized TEM Laura Coronado Bio 10 Chapter 15 Figure 15.8

  29. LM LM Colorized SEM (a) Actinomycete (b) Cyanobacteria (c) Giant bacterium Laura Coronado Bio 10 Chapter 15 Figure 15.9

  30. The Structure and Function of Prokaryotes • Some prokaryotes • Form true colonies • Show specialization of cells • Are very large • 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. Laura Coronado Bio 10 Chapter 15

  31. Colorized TEM Flagellum Plasmamembrane Cell wall Rotary movement of each flagellum Laura Coronado Bio 10 Chapter 15 Figure 15.10

  32. Procaryotic Reproduction • 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 Laura Coronado Bio 10 Chapter 15

  33. Colorized SEM Endospore Laura Coronado Bio 10 Chapter 15 Figure 15.11

  34. 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. • 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) Laura Coronado Bio 10 Chapter 15

  35. Nutritional Mode Energy Source Carbon Source Sunlight Photoautotroph CO2 Chemoautotroph Inorganic chemicals Sunlight Photoheterotroph Organic compounds Organic compounds Chemoheterotroph Laura Coronado Bio 10 Chapter 15 Figure 15.UN06

  36. MODES OF NUTRITION Energy source Light Chemical Photoautotrophs Chemoautotrophs Colorized TEM CO2 Elodea, an aquatic plant Bacteria from a hot spring Carbon source Chemoheterotrophs Photoheterotrophs Colorized TEM Organic compounds Rhodopseudomonas Little Owl (Athene noctua) Laura Coronado Bio 10 Chapter 15 Figure 15.12

  37. 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) • Some archaea are “extremophiles.” • Halophiles thrive in salty environments. • Thermophiles inhabit very hot water. • Methanogens inhabit the bottoms of lakes and swamps and aid digestion in cattle and deer. Laura Coronado Bio 10 Chapter 15

  38. (a) Salt-loving archaea (b) Heat-loving archaea Laura Coronado Bio 10 Chapter 15 Figure 15.13

  39. Bacteria and Humans • Bacteria interact with humans in many ways. • 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. Laura Coronado Bio 10 Chapter 15

  40. Colorized SEM Cells of nasal lining Haemophilus influenzae Laura Coronado Bio 10 Chapter 15 Figure 15.14

  41. The best defenses against bacterial disease are • Education • Sanitation • Antibiotics Laura Coronado Bio 10 Chapter 15

  42. SEM Tick that carries the Lyme disease bacterium Spirochete that causes Lyme disease “Bull’s-eye” rash Laura Coronado Bio 10 Chapter 15 Figure 15.15

  43. 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. Laura Coronado Bio 10 Chapter 15

  44. Laura Coronado Bio 10 Chapter 15 Figure 15.16

  45. 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. • Prokaryotes play essential roles in • Chemical cycles in the environment • The breakdown of organic wastes and dead organisms • Prokaryotes are used Bioremediation is the use of organisms to remove pollutants from • Water • Air • Soil • Decomposers in sewage treatment &petroleum spills. Laura Coronado Bio 10 Chapter 15

  46. Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi Outflow Liquid wastes Laura Coronado Bio 10 Chapter 15 Figure 15.17

  47. Laura Coronado Bio 10 Chapter 15 Figure 15.18

  48. PROTISTS • Protists • Are eukaryotic • Evolved from prokaryotic ancestors • Are ancestral to all other eukaryotes • Plants • Fungi • Animals Laura Coronado Bio 10 Chapter 15

  49. The Origin of Eukaryotic Cells • Eukaryotic cells evolved by • The infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system and • Endosymbiosis, one species living inside another host species, in which free-living bacteria came to reside inside a host cell, producing mitochondria and chloroplasts Laura Coronado Bio 10 Chapter 15

  50. Plasma membrane Photosynthetic prokaryote DNA Membrane infolding Cytoplasm (Some cells) Endosymbiosis Aerobic heterotrophic prokaryote Endoplasmic reticulum Ancestral prokaryote Chloroplast Nucleus Mitochondrion Nuclear envelope Photosynthetic eukaryotic cell Cell with nucleus and endomembrane system (a) Origin of the endomembrane system (b) Origin of mitochondria and chloroplasts Laura Coronado Bio 10 Chapter 15 Figure 15.20

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