Chapter 14: The History of Life

1. Chapter 14: The History of Life • Section 1—The Record of Life • Part 1—Types of Fossils

2. Chapter 14: The History of Life Why It’s Important Understanding the history of earth will provide us with a background for understanding the __________ of evolution theory

3. 14.1 Section Objectives – page 369 Section Objectives: • Identify the different types of fossils and how they are formed • Distinguish between Relative Dating and Radiometric Dating

4. New Vocabulary • Fossil • Plate Tectonics Review Vocabulary • Isotope – atoms of the same element that have different numbers of ___________, like carbon-12, 13, and 14. neutrons

5. Review • What is a scientific theory? Explanation that is supported by data

6. Section 14.1 Summary – pages 369-379 Early History of Earth • What was early Earth like? • probably very _______ • Energy from colliding _____________ could have heated its surface • decay of _______________ materials might have heated its interior hot meteorites radioactive

7. Section 14.1 Summary – pages 369-379 • Volcanoes might have frequently spewed ______ and _______, relieving some of the _____________ in Earth’s hot interior. lava gases pressure • These gases helped form Earth’s early __________________ atmosphere

8. Although the early atmosphere probably contained no ________ oxygen, other gases such as __________________, ____________, and water _________ were likely present free carbon dioxide vapor nitrogen

9. Review… • what is the chemical formula for water? • What is water vapor? H2O Gaseous form of H2O

10. If we think back to the water cycle, what process will turn liquid water into a gas, placing it into the atmosphere? • What process might turn liquid water into a solid? • These changes are __________ changes, so the formula for water vapor (or ice) is still _________ heat and evaporation freezing physical H2O

11. split • Only a chemical reaction can ________ H2O and release the oxygen • What organism actually does this? • Do you think they existed when the earth was very hot and did not have liquid water? plants no

12. Section 14.1 Summary – pages 369-379 • Scientists think that the earth is approximately ______ billions years old • About _____ billion years ago, Earth might have ___________ enough for the water in its atmosphere to _______________ • Result? • Millions of years of ________ and __________ • __________ formed 4.6 4.4 cooled condense rain lightning Oceans

13. Section 14.1 Summary – pages 369-379 History in Rocks • There is no direct evidence of the __________ years of Earth’s history. The oldest rocks that have been found on Earth formed about ______ billion years ago • Before then, they earth may have been too _______ for rocks to form or older rocks may have already ___________ away earliest 3.9 hot eroded

14. Section 14.1 Summary – pages 369-379 Fossils-Clues to the past • About 95 percent of the species that have existed are ____________—they no longer live on Earth. extinct • Evidence of these species exists as ___________ that are found in rock layers fossils

15. Trace fossil • _______________ • indirect evidence left by an animal, like a footprint, trail, or burrow • ___________ • when minerals in rock fill a space left by a decayed organism • ___________ • When organism buried in sediment decays and leaves a space • ___________ or __________________ • when ______________ fill in an organism • _____________ or _____________ preserved • when an entire organism is trapped in amber or ice Cast Mold Petrified Permineralized minerals Amber ice

16. kinds • Paleontologists use fossils to… • Determine the _______ of organisms that lived in the past and learn about their ___________ • Ex: T-rex is a carnivore • Gain knowledge about _____________ and _____________ • Ex: Where are T-rex’s located; what other plant fossils are there? What kind of climate was needed for survival? behavior geography climate

17. Section 14.1 Summary – pages 369-379 Fossil formation • For fossils to form, organisms usually have to be _________ in mud, sand, or clay soon after they die. • Otherwise, they will soon start to __________ buried decompose

18. Fossil Formation • Becoming a Fossil

19. Section 14.1 Summary – pages 369-379 Discovery! Death of Organism Exposed through erosion or earth quakes Covered by sediment layers Layers build up and compress

20. Section 14.1 Summary – pages 369-379 • Fossils are found in ______________ rocks • These rocks form at relatively ______ temperatures and pressures that may prevent damage to the organism sedimentary low • Fossils do not form in volcanic rock, which is called _________________.... it forms at temperatures and pressures that are too _______ • There are two ways to determine a fossil’s age… • ___________ dating • _______________ dating metamorphic high Relative Radiometric

21. Section 14.1 Summary – pages 369-379 Relative Dating • Comparing the position of fossils in different layers of rock to determine their __________ age Relative • If the rock layers have not been disturbed, the layers at the surface must be _________ than the deeper layers. younger

22. Relative Dating • The Grand Canyon: Evidence of Earth's Past

23. Section 14.1 Summary – pages 369-379 Relative dating 4 • Which layer contains the oldest fossils? 1 2 3 4

24. Section 14.1 Summary – pages 369-379 Radiometric Dating • Allows us to find the __________ ages of rocks by utilizing the radioactive ___________ in rocks. specific isotopes • A radioactive isotope is… • an atom with an __________ nucleus. • It continues to break down, or ________, until it becomes more stable • As it decays, it gives off ___________ unstable decay radiation

25. Section 14.1 Summary – pages 369-379 • Each radioactive isotope decays at its own __________ • So when we find a ___________ isotope in a fossil or rock layer, we know how long it has been there rate specific • The decay rate of a radioactive isotope is called its _________________. • After each half-life, _________ of the remaining isotope is left half-life half

26. Section 14.1 Summary – pages 369-379 How much is left after 2 half-lives? 25%

27. Section 14.1 Summary – pages 369-379 • The half life of ____________ -40 (K-40) is 1.3 billion years • The half-life of Carbon-14 (C-14) is _______ years • We use this isotope to date fossils that are less than __________ years old Potassium 5730 50,000

28. heated • If a rock has been _________, some of the radioactive isotopes may have been __________ • If this occurs, the age obtained will be _________________ lost inaccurate

29. Radiometric Dating • Radiometric Dating Video Clip

30. Objective 1 Identify the different types of fossils and how they are formed • Trace fossil • Mold • Cast • Petrified or permineralized • Amber or ice preserved A trace or clue left by an organism Ex. = footprint Empty space in rock left by an organism after it dies An empty space that is filled in by minerals The actual organism is filled in with minerals The organism is preserved in amber or ice

31. Objective 2 • Distinguish between Relative Dating and Radiometric Dating: Relative Dating: Approximates the age of the fossil by comparing it to the ages of the surrounding rock layers Radiometric Dating: Determines the age of the fossil by measuring the amount of radioactive isotopes remaining in the fossil