17–1 The Fossil Record A. Fossils and Ancient Life B. How Fossils Form

1. Section Outline • Section 17-1 • 17–1 The Fossil Record A. Fossils and Ancient Life B. How Fossils Form C. Interpreting Fossil Evidence 1. Relative Dating 2. Radioactive Dating D. Geologic Time Scale 1. Eras 2. Periods

2. Age of fossil with respect to another rock or fossil (that is, older or younger) • Age of a fossil in years • Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock • Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen • Imprecision and limitations of age data • Difficulty of radioassay laboratory methods • Compare/Contrast Table • Section 17-1 • Comparing Relative and Absolute Dating of Fossils • Relative Dating • Absolute Dating • Can determine • Is performed by • Drawbacks

3. Figure 17-2 Formation of a Fossil • Section 17-1 • Water carries small rock particles to lakes and seas. • Dead organisms are buried by layers of sediment, which forms new rock. • The preserved remains may later be discovered and studied.

4. Figure 17-5 Geologic Time Scale • Section 17-1 • (millions of years ago) • (millions of years ago) • Era • Period • Time • (millions of years ago) • Era • Period • Time • Era • Period • Time • Permian • Carboniferous • Devonian • Silurian • Ordovician • Cambrian • 290 – 245 • 360–290 • 410–360 • 440–410 • 505–440 • 544–505 • Quaternary • Tertiary • Cretaceous • Jurassic • Triassic • 1.8–present • 65–1.8 • 145–65 • 208–145 • 245–208 • Vendian • 650–544

5. Figure 17-5 Geologic Time Scale • Section 17-1 • (millions of years ago) • (millions of years ago) • Era • Period • Time • (millions of years ago) • Era • Period • Time • Era • Period • Time • Permian • Carboniferous • Devonian • Silurian • Ordovician • Cambrian • 290 – 245 • 360–290 • 410–360 • 440–410 • 505–440 • 544–505 • Quaternary • Tertiary • Cretaceous • Jurassic • Triassic • 1.8–present • 65–1.8 • 145–65 • 208–145 • 245–208 • Vendian • 650–544

6. Figure 17-5 Geologic Time Scale • Section 17-1 • (millions of years ago) • (millions of years ago) • Era • Period • Time • (millions of years ago) • Era • Period • Time • Era • Period • Time • Permian • Carboniferous • Devonian • Silurian • Ordovician • Cambrian • 290 – 245 • 360–290 • 410–360 • 440–410 • 505–440 • 544–505 • Quaternary • Tertiary • Cretaceous • Jurassic • Triassic • 1.8–present • 65–1.8 • 145–65 • 208–145 • 245–208 • Vendian • 650–544

7. Interest Grabber • Section 17-2 Mystery Detective • Earth is billions of years old. There were not any witnesses to those early years. How, then, can scientists determine the conditions on Earth long before there were any scientists? • Think about how you draw conclusions about occurrences that you did not witness. If you saw the charred remains of a house, for example, you could infer that it burned down.

8. Interest Grabber continued • Section 17-2 • 1. On a sheet of paper, list things that you can observe around you that lead you to infer about events you did not see. For example, what do skid marks in the roadway tell you? • 2. Now, think about and list the evidence all around you that scientists might analyze when trying to piece together a history of Earth. How would finding the fossil of a sea animal in the middle of a desert tell a scientist something about the past?

9. Section Outline • Section 17-2 • 17–2 Earth’s Early History A. Formation of Earth B. The First Organic Molecules C. How Did Life Begin? 1. Formation of Microspheres 2. Evolution of RNA and DNA D. Free Oxygen E. Origin of Eukaryotic Cells F. Sexual Reproduction and Multicellularity

10. Concept Map • Section 17-2 • Evolution of Life • Early Earth was hot; atmosphere contained poisonous gases. • Earth cooled and oceans condensed. • Simple organic molecules may have formed in the oceans.. • Small sequences of RNA may have formed and replicated. • First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. • Later prokaryotes were photosynthetic and produced oxygen. • An oxygenated atmosphere capped by the ozone layer protected Earth. • First eukaryotes may have been communities of prokaryotes. • Multicellular eukaryotes evolved. • Sexual reproduction increased genetic variability, hastening evolution.

11. Figure 17-8 Miller-Urey Experiment • Section 17-2 • Mixture of gases simulating atmospheres of early Earth • Spark simulating lightning storms • Cold water cools chamber, causing droplets to form • Condensation chamber • Water vapor • Liquid containing amino acids and other organic compounds

12. Figure 17-12 Endosymbiotic Theory • Section 17-2 • Chloroplast • Plants and plantlike protists • Aerobic bacteria • Ancient Prokaryotes • Photosynthetic bacteria • Nuclear envelope evolving • Mitochondrion • Primitive Photosynthetic Eukaryote • Animals, fungi, and non-plantlike protists • Primitive Aerobic Eukaryote • Ancient Anaerobic Prokaryote

13. Interest Grabber • Section 17-3 Team, Team, Team! • The first living things were unicellular. You, however, are multicellular. Is there an advantage to being multicellular?

14. Interest Grabber continued • Section 17-3 • 1. Make a list of at least six different organs in your body, and next to each, write the main function of that organ. • 2. Now, examine your list. Do any main functions overlap? Do two or more organs do exactly the same thing? • 3. Use your list to jog your memory, and write down the functions that must be performed by a unicellular organism. For example, you may have written that your nerves help you sense your environment. Doesn’t a cell need to sense its environment, too?