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Chapter 14.1 The Record of Life

Chapter 14.1 The Record of Life. I. EARLY HISTORY OF EARTH. Probably very hot Frequent volcanic eruptions Atmosphere had no oxygen Called a “reducing atmosphere” Did have the following Water vapor Carbon dioxide Nitrogen Earth is more than 4.6 Billion Years Old.

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Chapter 14.1 The Record of Life

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  1. Chapter 14.1 The Record of Life

  2. I. EARLY HISTORY OF EARTH • Probably very hot • Frequent volcanic eruptions • Atmosphere had no oxygen • Called a “reducing atmosphere” • Did have the following • Water vapor • Carbon dioxide • Nitrogen • Earth is more than 4.6 Billion Years Old

  3. I. EARLY HISTORY OF EARTH • 3.4 – 3.9 Billon years ago • Earth cooled enough for water to condense and become part of our oceans

  4. II. HISTORY IN ROCKS • Oldest rocks found on Earth are only 3.9 billion years old • Rocks are missing around 0.7 billion years of information, however, they are a very important source of information about the diversity of life on early Earth.

  5. II. HISTORY IN ROCKS • A. Fossils – Clues to the Past • About 95% of the species that have lived on Earth are now extinct • Fossil: evidence of an organism that lived long ago • There are many different types of fossils • Trace fossils • Casts • Molds • Amber-preserved or frozen fossils

  6. II. HISTORY IN ROCKS • A. Fossils – Clues to the Past • 1. Trace Fossils • Indirect evidence such as a footprint, trail or burrow • 2. Casts • When minerals fill in a space • 3. Molds • forms when an organism is buried in sediment, then decays leaving an empty space • 4. Amber-preserved fossil • Sometimes an entire organism can get trapped in ice or tree sap that hardens into amber.

  7. II. HISTORY IN ROCKS • B. Palentologists – “Dectectives of the Past” • Palentologists: scientists that study ancient life and use fossils to understand events that happened long ago. • also study fossils to also learn about ancient climates and geography

  8. II. HISTORY IN ROCKS • C. Fossil Formation: • Organisms usually have to be buried in sediment (mud, clay, sand) • They are covered, and natural pressure causes the organism to compress and harden into a type of rock • Sedimentary rock • Most fossils are located in lakes, streams, or oceans

  9. II. HISTORY IN ROCKS • D. Relative Dating: • Relative dating works like this • The Deeper the layer where the fossil is found, the older the fossil is • The higher up in the soil the fossil is found, the younger the fossil is.

  10. II. HISTORY IN ROCKS • E. Radiometric Dating: • Used to determine “actual” age of a fossil • Utilizes radioactive isotopes in rocks • Measures rate of isotope decay and compares to known standards • Unfortunately, Carbon-14 can only be used to date fossils that are less than 50,000 years old • Common radiometric dating isotope is Carbon-14 • Potassium-40 measures actual date up to 1.3 billion years old

  11. E. Radiometric Dating

  12. III. A TRIP THROUGH GEOLOGIC TIME • “Geologic Time Scale” • Based on Earth’s layers of rocks and fossils • A. The Geologic Time Scale • Divided into 4 large sections or “Eras” *(PPMC)* • Pre-Cambrian • Paleozoic • Mesozoic • Cenozoic • Each “Era” represents a LONG period of time • Distinguished by the types of organisms that lived during that period of time.

  13. III. A TRIP THROUGH GEOLOGIC TIME • B. Precambrian Era • Oldest fossils found are 3.4 b.y.o. • Mostly fossils of photosynthetic cyanobacteria • Also find stromatolites • Another photosynthetic structure • Accounts for 87% of Earth’s history • In the beginning, there were only unicellular prokaryotes (single-celled prokaryotic cells) • Cells that have no membrane-bound organelles and no true nucleus • Eukaryotic developed around 2.1 b.y.a. • End of precambrian came around 543 m.y.a.

  14. Cyanobacteria

  15. Stromatolites

  16. III. A TRIP THROUGH GEOLOGIC TIME • C. Paleozoic • From 543 m.y.a. to 248 m.y.a. • Enormous increase in biodiversity • Variety of plants and animals • Ocean life • Worms, sea stars, unusual arthropods • Fish • Oldest animals with backbones • Ferns and early seed plants • Four-legged amphibians • Towards the end, reptiles appeared • 1ST MASS EXTINCTION OCCURRED AT THE END

  17. III. A TRIP THROUGH GEOLOGIC TIME • D. Mesozoic • 248 m.y.a. to 65 m.y.a. • Early mammals • Small, mouse-like • Dinosaurs were present • Modern birds evolved from dinosaurs • Flowering plants appeared • Plate tectonics occurred during this time • 2ND MASS EXTINCTION OCCURRED • This is the extinction that killed dinosaurs • Meteorite collision

  18. III. A TRIP THROUGH GEOLOGIC TIME • E. Cenozoic • 65 m.y.a. to present • Mammals begin to flourish • Primates appeared right at 65 m.y marker • Modern humans appeared 200,000 y.a.

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