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The History of Life

The History of Life. The Fossil Record. Fossils & Ancient Life. Paleontologists Scientists Who Study Fossils Infer What Past Life Looked Like What They Ate & What Ate Them Behavior Environment They Lived In. What They Looked Like. What They Ate. Behavior & Environment. 3.6 MYA.

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The History of Life

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  1. The History of Life The Fossil Record

  2. Fossils & Ancient Life • Paleontologists • Scientists Who Study Fossils • Infer What Past Life • Looked Like • What They Ate & What Ate Them • Behavior • Environment They Lived In

  3. What They Looked Like

  4. What They Ate

  5. Behavior & Environment 3.6 MYA

  6. Fossils & Ancient Life • Fossil Record • Organization Of Fossils From Oldest To Newest Including Supporting Information Of Other Life Forms In Their Environment

  7. Fossils & Ancient Life Key Concept The Fossil Record Provides Evidence About The History Of Life On Earth. It Also Shows How Different Groups of Organisms Have Changed Over Time.

  8. Fossils & Ancient Life • Each Fossil Is Found Only In It’s Particular Time Period or Layer • A Kind Of Fossil Clock • Of All The Life Forms That Have Ever Lived On Earth ----- • 99% Are Extinct • No Longer Alive

  9. How Fossils Are Formed • Most Form In Sedimentary Rock • Plants & Animals Die In A Water Environment And Are Covered With Silt • Others Covered With Fine Sand or Volcanic Ash • Compressed Into Rock

  10. How Fossils Are Formed • Organic Materials Are Replaced By Minerals • Quality Of Preservation Varies • Fossils Include: • Bones • Eggs • Footprints • Skin Impressions, etc.

  11. Interpreting Fossil Evidence • Fossils Are Released By • Tectonic Forces • Erosion • Mining • Construction

  12. Interpreting Fossil Evidence • Most Fossils Disarticulated • Predation • Scavengers • Rot • Catastrophic Events May Bury & Preserve Whole Animals and/or Ecosystems

  13. Life On Earth

  14. Dating Fossils Two Types of Dating • Relative Dating Organizes Fossils By Order (1st, 2nd, 3rd, etc.) Tells You Which Organisms Lived In What Order Does Not Give You Actual Years • Absolute Dating Gives You Age In Years Before Present e.g. 150 Million Years Ago

  15. Relative Dating

  16. Relative Dating

  17. Relative Dating • The Age of a Fossil Is Determined By Comparing Its Placement With Other Fossils In Other Layers Of Sedimentary Rock • Allows Comparison Of Layers World Wide

  18. Relative Dating • Index Fossils • Easily Recognized • Existed For A Short (?) Period • Wide Geographic Distribution • Does Not Give Absolute Age

  19. Relative Dating Key Concept: Relative Dating Allows Paleontologists To Estimate A Fossils Age Compared With That Of Other Fossils

  20. Radioactive Dating Uses The Half Lives Of Certain Radioactive Isotopes In Igneous Rocks To Calculate The Age Of A Fossil Half Life The Length Of Time Required For Half Of The Radioactive Atoms In A Sample To Decay

  21. Radioactive Dating Key Concept: In Radioactive Dating, Scientists Calculate The Age Of A Sample Based On The Amount Of Remaining Radioactive Isotopes It Contains

  22. Radioactive Dating Different Radioactive Elements Have Different “tick rates” Carbon-14 Half-life = 5,730 years Decays to Nitrogen-14 Useful Back 60,000 years

  23. Absolute Age Radioactive Dating

  24. Geologic Time Scale Developed By Paleontologists To Classify Geologic And Biologic Events Rock Layers Fossils Present

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