1. Foothill High School Science Department The History of Life The Fossil Record

2. Foothill High School Science Department Fossils & Ancient Life Paleontologists Paleontologists – Scientists Who Study Fossils – Infer What Past Life Looked Like Looked Like What They Ate & What Ate Them What They Ate & What Ate Them Behavior Behavior Environment They Lived In Environment They Lived In

3. What They Looked Like

4. Foothill High School Science Department What They Ate

5. Foothill High School Science Department Behavior & Environment 3.6 MYA

6. Foothill High School Science Department Fossils & Ancient Life Fossil Record Fossil Record – Organization Of Fossils From Oldest To Newest Including Supporting Information Of Other Life Forms In Their Environment

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

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

10. Foothill High School Science Department How Fossils Are Formed Organic Materials Are Replaced By Minerals Organic Materials Are Replaced By Minerals Quality Of Preservation Varies Quality Of Preservation Varies Fossils Include: Fossils Include: – Bones – Eggs – Footprints – Skin Impressions, etc.

11. Foothill High School Science Department Interpreting Fossil Evidence Fossils Are Released By Fossils Are Released By – Tectonic Forces – Erosion – Mining – Construction

12. Foothill High School Science Department Interpreting Fossil Evidence Most Fossils Disarticulated Most Fossils Disarticulated – Predation – Scavengers – Rot Catastrophic Events May Bury & Preserve Whole Animals and/or Ecosystems Catastrophic Events May Bury & Preserve Whole Animals and/or Ecosystems

13. Foothill High School Science Department Life On Earth

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

15. Foothill High School Science Department Relative Dating

16. Foothill High School Science Department Relative Dating

17. Foothill High School Science Department Relative Dating The Age of a Fossil Is Determined By Comparing Its Placement With Other Fossils In Other Layers Of Sedimentary Rock 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. Foothill High School Science Department Relative Dating Index Fossils Index Fossils – Easily Recognized – Existed For A Short (?) Period – Wide Geographic Distribution – Does Not Give Absolute Age

19. Foothill High School Science Department Relative Dating Key Concept: Relative Dating Allows Paleontologists To Estimate A Fossils Age Compared With That Of Other Fossils

20. Foothill High School Science Department 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. Foothill High School Science Department 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. Foothill High School Science Department 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 Isotope Stable Daughter Parent Half-Life (years) Range (years) Sample Material Carbon 14 Nitrogen 14 5,730 20 to 60,000 Carbon Bearing Plants, Animals Potassium 40 Argon 40 1.3 Billion 50,000 to 4.6 Billion Volcanic igneous rocks; micas, feldspars, hornblend Rubidium 87 Strontium 87 48.8 Billion 10 Million to 4.6 Billion Metamorphic and igneous rocks; feldspars, micas, hornblend Thorium 232 Lead 208 14 Billion 10 Million Zircon, Uranium & Thorium Uranium 235 Lead 207 704 Million 4.6 Billion Uranium 238 Lead 206 4.5 Billion

24. Foothill High School Science Department Geologic Time Scale Developed By Paleontologists To Classify Geologic And Biologic Events Rock Layers Fossils Present