3. Table of Contents – pages iv-v Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through TimeChange Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: Invertebrates Unit 9: Vertebrates Unit 10: The Human Body

4. Table of Contents – pages iv-v Unit 1: What is Biology? Chapter 1: Biology: The Study of Life Unit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and Conservation Unit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell

5. Table of Contents – pages iv-v Unit 4: Genetics Chapter 10: Mendel and Meiosis Chapter 11: DNA and Genes Chapter 12: Patterns of Heredity and Human Genetics Chapter 13: Genetic Technology Unit 5: Change Through TimeChange Through Time Chapter 14: The History of LifeThe History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity

6. Table of Contents – pages iv-v Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18: Viruses and Bacteria Chapter 19: Protists Chapter 20: Fungi Unit 7: Plants Chapter 21: What Is a Plant? Chapter 22: The Diversity of Plants Chapter 23: Plant Structure and Function Chapter 24: Reproduction in Plants

7. Table of Contents – pages iv-v Unit 8: Invertebrates Chapter 25: What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates

8. Table of Contents – pages iv-v Unit 9: Vertebrates Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds Chapter 32: Mammals Chapter 33: Animal Behavior Unit 10: The Human Body Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development Chapter 39: Immunity from Disease

9. Unit Overview – pages 366-367 Changes Through Time The History of Life The Theory of Evolution Primate Evolution Organizing Life’s Diversity

10. Chapter Contents – page ix Chapter 14 The History of LifeThe History of Life 14.1: The Record of LifeThe Record of Life 14.1: Section CheckSection Check 14.2: The Origin of LifeThe Origin of Life 14.2: Section CheckSection Check Chapter 14 SummarySummary Chapter 14 AssessmentAssessment

11. Chapter Intro-page 368 What You’ll Learn You will examine how rocks and fossils provide evidence of changes in Earth’s organisms. You will correlate the geologic time scale with biological events. You will sequence the steps by which small molecules may have produced living cells.

12. 14.1 Section Objectives – page 369 Identify the different types of fossils and how they are formed Section Objectives: Summarize the major events of the geologic time scale.

13. Section 14.1 Summary – pages 369-379 What was early Earth like? Some scientists suggest that it was probably very hot. The energy from colliding meteorites could have heated its surface, while both the compression of minerals and the decay of radioactive materials heated its interior. Early History of Earth

14. Section 14.1 Summary – pages 369-379 Volcanoes might have frequently spewed lava and gases, relieving some of the pressure in Earth’s hot interior. These gases helped form Earth’s early atmosphere. Early History of Earth

15. Section 14.1 Summary – pages 369-379 About 4.4 billion years ago, Earth might have cooled enough for the water in its atmosphere to condense. This might have led to millions of years of rainstorms with lightning—enough rain to fill depressions that became Earth’s oceans. Early History of Earth

16. Section 14.1 Summary – pages 369-379 There is no direct evidence of the earliest years of Earth’s history. The oldest rocks that have been found on Earth formed about 3.9 billion years ago. History in Rocks Although rocks cannot provide information about Earth’s infancy, they are an important source of information about the diversity of life that has existed on the planet.

17. Section 14.1 Summary – pages 369-379 About 95 percent of the species that have existed are extinct—they no longer live on Earth. Fossils-Clues to the past Among other techniques, scientists study fossils to learn about ancient species.

18. Section 14.1 Summary – pages 369-379 A fossil is evidence of an organism that lived long ago that is preserved in Earth’s rocks. Fossils-Clues to the past Types of Fossils Fossils Types Formation Trace fossils Casts Molds Petrified/ Permineralized fossils Amber- Preserved or frozen fossils A trace fossil is any indirect evidence left by an animal and may include a footprint, a trail, or a burrow. When minerals in rocks fill a space left by a decayed organism, they make a replica, or cast, of the organism. A mold forms when an organism is buried in sediment and then decays, leaving an empty space. Petrified-minerals sometimes penetrate and replace the hard parts of an organism. Permineralized-void spaces in original organism infilled by minerals. At times, an entire organism was quickly trapped in ice or tree sap that hardened into amber.

19. Section 14.1 Summary – pages 369-379 Paleontologists, scientists who study ancient life, are like detectives who use fossils to understand events that happened long ago. Paleontologists-Detectives to the past They use fossils to determine the kinds of organisms that lived during the past and sometimes to learn about their behavior.

20. Section 14.1 Summary – pages 369-379 Paleontologists also study fossils to gain knowledge about ancient climate and geography. Paleontologists-Detectives to the past By studying the condition, position, and location of rocks and fossils, geologists and paleontologists can make deductions about the geography of past environments.

21. Section 14.1 Summary – pages 369-379 For fossils to form, organisms usually have to be buried in mud, sand, or clay soon after they die. Fossil formation Most fossils are found in sedimentary rocks. These rocks form at relatively low temperatures and pressures that may prevent damage to the organism.

22. Section 14.1 Summary – pages 369-379 Fossils are not usually found in other types of rock because of the ways those rocks form. For example, the conditions under which metamorphic rocks form often destroy any fossils that were in the original sedimentary rock. Fossil formation

23. Section 14.1 Summary – pages 369-379 Few organisms become fossilized because, without burial, bacteria and fungi immediately decompose their dead bodies. Occasionally, however, organisms do become fossils in a process that usually takes many years. The Fossilization Process

24. Section 14.1 Summary – pages 369-379 The Fossilization Process A Protoceratops drinking at a river falls into the water and drowns Sediments from upstream rapidly cover the body, slowing its decomposition. Minerals from the sediments seep into the body. Over time, additional layers of sediment compress the sediments around the body, forming rock. Minerals eventually replace all the body’s bone material. Earth movements or erosion may expose the fossil millions of years after it formed.

25. Section 14.1 Summary – pages 369-379 Scientists use a variety of methods to determine the age of fossils. One method is a technique called relative dating. Relative dating If the rock layers have not been disturbed, the layers at the surface must be younger than the deeper layers.

26. Section 14.1 Summary – pages 369-379 The fossils in the top layer must also be younger than those in deeper layers. Relative dating Using this principle, scientists can determine relative age and the order of appearance of the species that are preserved as fossils in the layers.

27. Section 14.1 Summary – pages 369-379 To find the specific ages of rocks, scientists use radiometric dating techniques utilizing the radioactive isotopes in rocks. Radiometric dating Recall that radioactive isotopes are atoms with unstable nuclei that break down, or decay, over time, giving off radiation. A radioactive isotope forms a new isotope after it decays.

28. Section 14.1 Summary – pages 369-379 Because every radioactive isotope has a characteristic decay rate, scientists use the rate of decay as a type of clock. Radiometric dating The decay rate of a radioactive isotope is called its half-life.

29. Section 14.1 Summary – pages 369-379 Scientists try to determine the approximate ages of rocks by comparing the amount of a radioactive isotope and the new isotope into which it decays. Radiometric dating

30. Section 14.1 Summary – pages 369-379 Scientists use potassium-40, a radioactive isotope that decays to argon-40, to date rocks containing potassium bearing minerals. Based on chemical analysis, chemists have determined that potassium-40 decays to half its original amount in 1.3 billion years. Radiometric dating

31. Section 14.1 Summary – pages 369-379 Scientists use carbon-14 to date fossils less than 70 000 years old. Again, based on chemical analysis, they know that carbon-14 decays to half its original amount in 5730 years. Radiometric dating

32. Section 14.1 Summary – pages 369-379 Scientists always analyze many samples of a rock using as many methods as possible to obtain consistent values for the rock’s age. Errors can occur if the rock has been heated, causing some of the radioactive isotopes to be lost or gained. Radiometric dating

33. Section 14.1 Summary – pages 369-379 By examining sequences containing sedimentary rock and fossils and dating some or the igneous or metamorphic rocks that are found in the sequences, scientists have put together a chronology, or calendar, of Earth’s history. A Trip Through Geologic Time This chronology, called the geologic time scale, is based on evidence from Earth’s rocks and fossils.

34. Section 14.1 Summary – pages 369-379 Rather than being based on months or even years, the geologic time scale is divided into four large sections, the Precambrian (pree KAM bree un) Era, the Paleozoic (pay lee uh ZOH ihk) Era, the Mesozoic (me zuh ZOH ihk) Era, and the Cenozoic (se nuh ZOH ihk) Era. The geologic time scale

35. Section 14.1 Summary – pages 369-379 An era is a large division in the scale and represents a very long period of time. The geologic time scale Each era is subdivided into periods.

36. Section 14.1 Summary – pages 369-379 The geologic time scale The divisions in the geologic time scale are distinguished by the organisms that lived during that time interval.

37. Section 14.1 Summary – pages 369-379 The fossil record indicates that there were several episodes of mass extinction that fall between time divisions. The geologic time scale A mass extinction is an event that occurs when many organisms disappear from the fossil record almost at once. The geologic time scale begins with the formation of Earth about 4.6 billion years ago.

38. Section 14.1 Summary – pages 369-379 The oldest fossils are found in Precambrian rocks that are about 3.4 billion years old. Life during the Precambrian Scientists found these fossils, in rocks found in the deserts of western Australia. The fossils resemble the forms of modern species of photosynthetic cyanobacteria.

39. Section 14.1 Summary – pages 369-379 Scientists have also found dome-shaped structures called stromatolites (stroh MAT ul ites) in Australia and on other continents. Life during the Precambrian Stromatolites still form today in Australia from mats of cyanobacteria. Thus, the stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian.

40. Section 14.1 Summary – pages 369-379 The Precambrian accounts for about 87 percent of Earth’s history. Life during the Precambrian At the beginning of the Precambrian, unicellular prokarotes—cells that do not have a membrane-bound nucleus— appear to have been the only life forms on Earth.

41. Section 14.1 Summary – pages 369-379 About 1.8 billion years ago, the fossil record shows that more complex eukaryotic organisms, living things with membrane-bound nuclei in their cells, appeared. Life during the Precambrian Major Life Form Major Events Period Era Million Years Ago Precambrian 4000 3500 1800 Life evolves Prokaryotes Eukaryotes Invertebrates

42. Section 14.1 Summary – pages 369-379 By the end of the Precambrian, about 543 million years ago, multicellular eukaryotes, such as sponges and jelly- fishes, diversified and filled the oceans. Life during the Precambrian

43. Section 14.1 Summary – pages 369-379 In the Paleozoic Era, which lasted until 248 million years ago, many more types of animals and plants were present on Earth, and some were preserved in the fossil record. Diversity during the Paleozoic During the Cambrian Period, the oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods.

44. Section 14.1 Summary – pages 369-379 During the first half of the Paleozoic, fishes, the oldest animals with backbones, appeared in Earth’s waters. Diversity during the Paleozoic There is also fossil evidence of ferns and early seed plants existing on land about 400 million years ago. Around the middle of the Paleozoic, four-legged animals such as amphibians appeared on Earth.

45. Section 14.1 Summary – pages 369-379 During the last half of the era, the fossil record shows that reptiles appeared and began to flourish on land. Diversity during the Paleozoic Million Years Ago 543491443417354323290 Paleozoic Era Cambrian OrdovicianSilurian Devonian CarboniferousPermian First vertebrates First land plants First jawed fishes First seed plants First amphibians First reptiles Conifers dominant

46. Section 14.1 Summary – pages 369-379 The largest mass extinction recorded in the fossil record marked the end of the Paleozoic. Diversity during the Paleozoic About 90 percent of Earth’s marine species and 70 percent of the land species disappeared at this time.

47. Section 14.1 Summary – pages 369-379 The Mesozoic Era began about 248 million years ago. Life in the Mesozoic The Mesozoic Era is divided into three periods. Fossils from the Triassic Period, the oldest period, show that mammals appeared on Earth at this time.

48. Section 14.1 Summary – pages 369-379 These fossils of mammals indicate that early mammals were small and mouse- like. Life in the Mesozoic 248 206 144 Mesozoic Era TriassicJurassicCretaceous First dinosaurs First mammals First flowering plants First birds Flowering plants dominant Period Million Years Ago Era

49. Section 14.1 Summary – pages 369-379 The middle of the Mesozoic, called the Jurassic Period, began about 206 million years ago. 248 206 144 Mesozoic Era TriassicJurassicCretaceous First dinosaurs First mammals First flowering plants First birds Flowering plants dominant Period Million Years Ago Era Life in the Mesozoic

50. Section 14.1 Summary – pages 369-379 Recent fossil discoveries support the idea that modern birds evolved from one of the groups of dinosaurs toward the end of this period. Life in the Mesozoic

51. Section 14.1 Summary – pages 369-379 The last period in the Mesozoic, the Cretaceous, began about 144 million years ago. A mass extinction During this period, many new types of mammals appeared and flowering plants flourished on Earth.

52. Section 14.1 Summary – pages 369-379 A mass extinction Some scientists propose that a large meteorite collision caused this mass extinction. The mass extinction of the dinosaurs marked the end of the Cretaceous Period about 65 million years ago.

53. Section 14.1 Summary – pages 369-379 The theory of continental drift, suggests that Earth’s continents have moved during Earth’s history and are still moving today at a rate of about six centimeters per year. Changes during the Mesozoic

54. Section 14.1 Summary – pages 369-379 Changes during the Mesozoic

55. Section 14.1 Summary – pages 369-379 Changes during the Mesozoic The theory for how the continents move is called plate tectonics. According to this idea, Earth’s surface consists of several rigid plates that drift on top of a plastic, partially molten layer of rock. These plates are continually moving- spreading apart, sliding by, or pushing against each other. The movements affect organisms.

56. Section 14.1 Summary – pages 369-379 The Cenozoic Era The Cenozoic began about 65 million years ago. It is the era in which you now live. Mammals began to flourish during the early part of this era. Primates first appeared approximately 75 million years ago and have diversified greatly.

57. Section 14.1 Summary – pages 369-379 The modern human species appeared perhaps as recently as 200,000 years ago. Mammals dominant Humans evolve TertiaryQuaternary Cenozoic Era 65 1.8 Period Era Million Years Ago The Cenozoic Era

58. Section 1 Check Question 1 D. the organisms that lived during that time interval C. periodic episodes of mass extinction B. dates based upon radioactive isotope decay What determines the divisions in the geologic time scale? A. the types of rock formed during the different divisions

59. Section 1 Check The answer is D, the organisms that lived during that time interval.

60. Section 1 Check Question 2 How can scientists determine when a mass extinction occurred in Earth’s history? Answer The fossils from a large percentage of species disappear from the fossil record almost at once.

61. Section 1 Check Question 3 D. land plants C. reptiles B. mammals What organisms have occupied Earth for the longest period of time? A. single-celled organisms

62. Section 1 Check The answer is A. Single-celled organisms have been present on the Earth since the Precambrian period and are still present today.

63. Section 1 Check Question 4 Given that volcanoes have erupted since Earth’s early history, why does volcanic rock not contain many fossils? Answer Lava is subject to high heat and strong pressure changes that prevent fossils from forming in it.

64. Section 1 Check Question 5 If scientists discover an early human fossil lying next to a dinosaur fossil, might they infer that some early humans actually lived at the time of dinosaurs? Answer The answer is no. The two fossils may have come to lie next to one another because of the effects of erosion, earth movements, the movement of water, or other artificial means.

65. 14.2 Section Objectives – page 380 Analyze early experiments that support the concept of biogenesis. Section Objectives: Review, analyze, and critique modern theories of the origin of life. Relate hypotheses about the origin of cells to the environmental conditions of early Earth.

66. Section 14.2 Summary – pages 380-385 Origins: The Early Idea Such observations led people to believe in spontaneous generation—the idea that nonliving material can produce life. In the past, the ideas that decaying meat produced maggots, mud produced fishes, and grain produced mice were reasonable explanations for what people observed occurring in their environment.

67. Section 14.2 Summary – pages 380-385 In 1668, an Italian physician, Francesco Redi, disproved a commonly held belief at the time—the idea that decaying meat produced maggots, which are immature flies. Spontaneous generation is disproved

68. Section 14.2 Summary – pages 380-385 Spontaneous generation is disproved Redi’s well-designed, controlled experiment successfully convinced many scientists that maggots, and probably most large organisms, did not arise by spontaneous generation. Control group Time Experimental group

69. Section 14.2 Summary – pages 380-385 However, during Redi’s time, scientists began to use the latest tool in biology—the microscope. Although Redi had disproved the spontaneous generation of large organisms, many scientists thought that microorganisms were so numerous and widespread that they must arise spontaneously-probably from a vital force in the air. Spontaneous generation is disproved

70. Section 14.2 Summary – pages 380-385 Pasteur’s experiments In the mid-1800s, Louis Pasteur designed an experiment that disproved the spontaneous generation of microorganisms. Pasteur set up an experiment in which air, but no microorganisms, was allowed to contact a broth that contained nutrients.

71. Section 14.2 Summary – pages 380-385 Pasteur’s experiments Each of Pasteur’s broth-filled flasks was boiled to kill all microorganisms. The flask’s S-shaped neck allowed air to enter, but prevented microorganisms from entering the flask. Pasteur tilted a flask, allowing the microorganisms to enter the broth. Microorganisms soon grew in the broth, showing that they come from other microorganisms.

72. Section 14.2 Summary – pages 380-385 Pasteur’s experiments Pasteur’s experiment showed that microorganisms do not simply arise in broth, even in the presence of air. From that time on, biogenesis (bi oh JEN uh sus), the idea that living organisms come only from other living organisms, became a cornerstone of biology.

73. Section 14.2 Summary – pages 380-385 Origins: The Modern Ideas No one has yet proven scientifically how life on Earth began. However, scientists have developed theories about the origin of life on Earth from testing scientific hypotheses about conditions on early Earth.

74. Section 14.2 Summary – pages 380-385 Simple organic molecules formed Scientists hypothesize that two developments must have preceded the appearance of life on Earth. First, simple organic molecules, or molecules that contain carbon, must have formed. Then these molecules must have become organized into complex organic molecules such as proteins, carbohydrates, and nucleic acids that are essential to life.

75. Section 14.2 Summary – pages 380-385 Simple organic molecules formed In the 1930s, a Russian scientist, Alexander Oparin, hypothesized that life began in the oceans that formed on early Earth. He suggested that energy from the sun, lightning, and Earth’s heat triggered chemical reactions to produce small organic molecules from the substances present in the atmosphere.

76. Section 14.2 Summary – pages 380-385 Simple organic molecules formed Then, rain probably washed the molecules into the oceans to form what is often called a primordial soup. In 1953, two American scientists, Stanley Miller and Harold Urey, tested Oparin’s hypothesis by simulating the conditions of early Earth in the laboratory.

77. Section 14.2 Summary – pages 380-385 Simple organic molecules formed

78. Section 14.2 Summary – pages 380-385 The formation of protocells The next step in the origin of life, as proposed by some scientists, was the formation of complex organic compounds. In the 1950s, various experiments were performed and showed that if the amino acids are heated without oxygen, they link and form complex molecules called proteins. A similar process produces ATP and nucleic acids from small molecules.

79. Section 14.2 Summary – pages 380-385 The formation of protocells The work of American biochemist Sidney Fox in 1992 showed how the first cells may have occurred. Fox produced protocells by heating solutions of amino acids. A protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.

80. Section 14.2 Summary – pages 380-385 The Evolution of Cells Fossils indicate that by about 3.4 billion years ago, photosynthetic prokaryotic cells existed on Earth. But these were probably not the earliest cells.

81. Section 14.2 Summary – pages 380-385 The first forms of life may have been prokaryotic forms that evolved from a protocell. Because Earth’s atmosphere lacked oxygen, scientists have proposed that these organisms were most likely anaerobic. The first true cells

82. Section 14.2 Summary – pages 380-385 For food, the first prokaryotes probably used some of the organic molecules that were abundant in Earth’s early oceans. Over time, these heterotrophs would have used up the food supply. The first true cells

83. Section 14.2 Summary – pages 380-385 However, organisms that could make food had probably evolved by the time the food was gone. These first autotrophs were probably similar to present-day archaebacteria. The first true cells

84. Archaebacteria (ar kee bac TEER ee uh) are prokaryotic and live in harsh environments, such as deep-sea vents and hot springs. The first true cells Section 14.2 Summary – pages 380-385

85. The first true cells The earliest autotrophs probably made glucose by chemosynthesis rather than by photosynthesis. In chemosynthesis, autotrophs release the energy of inorganic compounds, such as sulfur compounds, in their environment to make their food.

86. Section 14.2 Summary – pages 380-385 Photosynthesizing prokaryotes Photosynthesizing prokaryotes might have been the next type of organism to evolve. As the first photosynthetic organisms increased in number, the concentration of oxygen in Earth’s atmosphere began to increase. Organisms that could respire aerobically would have evolved and thrived.

87. Section 14.2 Summary – pages 380-385 The presence of oxygen in Earth’s atmosphere probably affected life on Earth in another important way. The sun’s rays would have converted much of the oxygen into ozone molecules that would then have formed a layer that contained more ozone than the rest of the atmosphere. Photosynthesizing prokaryotes

88. Section 14.2 Summary – pages 380-385 The endosymbiont theory Complex eukaryotic cells probably evolved from prokaryotic cells. The endosymbiont theory,proposed by American biologist Lynn Margulis in the early 1960s, explains how eukaryotic cells may have arisen. The endosymbiont theory proposes that eukaryotes evolved through a symbiotic relationship between ancient prokaryotes.

89. Section 14.2 Summary – pages 380-385 Prokaryote Aerobic bacteria Mitochondria Cyanobacteria Chloroplasts Animal Cell Plant cell A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote. Over a long time, the aerobes become mitochondria, no longer able to live on their own. Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments. The cyanobacteria become chloroplasts, no longer able to live on their own. The endosymbiont theory

90. Section 14.2 Summary – pages 380-385 New evidence from scientific research supports this theory and has shown that chloroplasts and mitochondria have their own ribosomes that are similar to the ribosomes in prokaryotes. In addition, both chloroplasts and mitochondria reproduce independently of the cells that contain them. The endosymbiont theory

91. Section 14.2 Summary – pages 380-385 The fact that some modern prokaryotes live in close association with eukaryotes also supports the theory. The endosymbiont theory

92. Section 2 Check Question 1 Why did some scientists still believe in spontaneous generation after Francesco Redi’s experiments? Answer Although Redi disproved the spontaneous generation of large organisms, many scientists still believed microorganisms were so numerous and widespread that they must arise spontaneously from the air.

93. Section 2 Check Question 2 What is the difference between biogenesis and spontaneous generation? Answer Spontaneous generation is the idea that life can come from nonliving material. Biogenesis is the idea that living organisms can come only from other living organisms.

94. Section 2 Check Question 3 What two molecular developments must have preceded the appearance life on Earth? Answer The formation of simple organic molecules, and the organization of simple organic molecules into complex organic molecules like proteins, carbohydrates and nucleic acids that are essential to life.

95. Section 2 Check Question 4 Who provided evidence to support Oparin’s hypothesis that life began in the oceans on early Earth? D. Stanley Miller and Harold Urey C. Francesco Redi B. Louis Pasteur A. Sidney Fox

96. Section 2 Check The answer is D, Stanley Miller and Harold Urey.

97. Chapter Summary – 14.1 Fossils provide a record of life on Earth. Fossils come in many forms, such as a leaf imprint, a worm burrow, or a bone. The Record of Life By studying fossils, scientists learn about the diversity of life and about the behavior of ancient organisms.

98. Chapter Summary – 14.1 Fossils can provide information on ancient environments. For example, fossils can help to predict whether an area had been a river environment, terrestrial environment, or a marine environment. In addition, fossils may provide information on ancient climates. The Record of Life

99. Chapter Summary – 14.1 Earth’s history is divided into the geologic time scale, based on evidence in rocks and fossils. The Record of Life The four major divisions in the geologic time scale are the Precambrian, Paleozoic Era, Mesozoic Era, and Cenozoic Era. The eras are further divided into periods.

100. Chapter Summary – 14.2 Francesco Redi and Louis Pasteur designed controlled experiments to disprove spontaneous generation. Their experiments and others like them convinced scientists to accept biogenesis. The Origin of Life Small organic molecules might have formed from substances present in Earth’s early atmosphere and oceans. Small organic molecules can form complex organic molecules.

101. Chapter Summary – 14.2 The earliest organisms were probably anaerobic, heterotrophic prokaryotes. Over time, chemosynthetic prokaryotes evolved and then photosynthetic prokaryotes that produced oxygen evolved, changing the atmosphere and triggering the evolution of aerobic cells and eukaryotes. The Origin of Life

102. Chapter Assessment Question 1 Is metamorphic rock a good source of fossils? Answer No, the conditions under which metamorphic rocks form often destroy any fossils contained in the original sedimentary rock.

103. Chapter Assessment Question 2 Why do scientists use relative dating techniques? Answer Relative dating allows scientists to compare the age and order of appearance of a fossil relative to those of the fossils appearing in the sedimentary layers above or below it.

104. Chapter Assessment Question 3 Why do organisms that die on the surface of the ground rarely become fossils? Answer Bacteria and fungi immediately decompose organisms exposed to the air.

105. Chapter Assessment Question 4 Why are dinosaur exhibits in museums rarely composed of real bones? Answer Minerals from sediments that covered dead dinosaurs seeped into the dinosaur’s body and eventually replaced all the body’s bone material.

106. Chapter Assessment Question 5 Scientists use the carbon-14 isotope to date fossils that are _______ years old. A. less than 70 000 B. more than one million C. 25 000 D. more than five million

107. Chapter Assessment The answer is A, less than 70 000.

108. Chapter Assessment Question 6 About how many years ago do fossils indicate that photosynthetic prokaryotic cells existed on Earth? A. 5.4 billion years B. 3.4 billion years C. 1.8 billion years D. 543 million years The answer is B, 3.4 billion years.

109. Chapter Assessment Question 7 Which forms of life developed earlier, anaerobic single-celled organisms or aerobic single-celled organisms, and why? Answer The answer is anaerobic single-celled organisms. Anaerobic single-celled organisms developed at a time when Earth’s atmosphere lacked oxygen. Aerobic organisms, which require oxygen to survive, developed later, when Earth’s atmosphere contained a supply of oxygen.

110. Chapter Assessment Question 8 Why are archaebacteria able to survive in harsh environments where most other organisms cannot? Answer Archaebacteria can release the energy of inorganic compounds in their environment to make their food rather than rely upon other organisms for their food.

111. Chapter Assessment Question 9 What was the importance of Earth’s ozone layer to the development of early organisms? Answer The ozone layer shielded early organisms from the harmful effects of ultraviolet radiation and enabled the evolution of more complex organisms.

112. Chapter Assessment Question 10 In Miller and Urey’s laboratory experiment to simulate the atmospheric conditions of early Earth, what atmospheric condition did the condenser simulate?

113. Chapter Assessment The condenser simulated rain in the atmosphere that washed organic molecules into the ocean. High voltage source Solution of organic compounds Condenser for cooling Boiling water Electrode Entry for hydrogen, methane, and ammonia gases

114. Chapter Assessment Photo Credits Corbis Alton Biggs

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116. End of Chapter 14 Show