1. The History of Life
Chapter 14

2. How the Earth Was Made: The Birth of the Earth Video

3. I. Paleontologists A. Scientists who study ancient life
1. Kinds of organisms
2. Ancient climate
3. Geography

4. II. Early History of Earth
A.Very hot
B. Volcanoes spewing lava and gases
C. Little oxygen in the atmosphere but lots of CO2, nitrogen and water vapor
What were conditions like on Early Earth?

5. II. Early History of Earth
Earth Cools
-lava cools (forms lands)
-rains for millions of years (forms oceans
-3.8 bya
What were conditions like on Early Earth?

6. III. Fossils A. Sedimentary rocks contain fossils- clues to the past
B. Oldest rocks 3.9 BILLION years old.
Can scientists be sure the Earth formed in this way?
How old are the oldest fossils?

7. III. Fossils The Fossilization process

8. III. Fossils D. Mold (empty space)
E. Casts (minerals fill a space left by decayed organism)
F. Trace fossils (indirect
G. Petrified (hardened/permineralized)
H. Amber preserved (quickly trapped in sap & hardened)
I. Frozen (preserved in ice)

9. V. The Age of a Fossil A. Relative Dating
1. Determined by dating the rocks in the layer above and below the fossil
a. Newspaper example
2. An estimate of age
Have some newspapers and leaves for them to stack

10. V. The Age of a Fossil B. Radiometric Dating
1. Determination of how many of the original atoms are left in the rock.
a. Atoms decay at a steady rate
2. Half-life- Time needed for ½ the atoms to decay
a. If the fossil’s half-life is 2 million years, when ½ of its atoms are gone it will be 2 million years old.
Have some newspapers and leaves for them to stack

11. V. The Age of a Fossil
3. Scientists use potassium-40 to date the oldest rocks and carbon-14 to date younger fossils
a. Draw example on board
4. Errors can occur if the rock has been heated (atoms are lost or gained).
Have some newspapers and leaves for them to stack

12. VI. The Geologic Time Scale
A. Four Eras
1. Precambrian
2. Paleozoic
3. Mesozoic
4. Cenozoic

13. VII. Life in the Precambrian (4600-543 MYA)
A. Earth’s formation
B. Prokaryotes
1. Cynobacteria-like
2. Stromatolites
C. 1.8 BYA eukaryotes evolve
D. 87% of Earth’s history
1.(January-October)

14. VIII. The Paleozoic Era 543 MYA – 245 MYA
A. Cambrian explosion of life!
1. Worms, sea stars, arthropods, fishes
MYA, ferns & early seed plants
3.Amphibians, reptiles

15. End of the Paleozoic B. Largest mass extinction
1. 90% of marine species extinct
2. 70% of land species extinct
Why was there such a mass extinction?
New models just not working out
Conditions changing rapidly
30%
70%

16. IX. Mesozoic 245 MYA – 66 MYA A. Triassic period 1. Mammals (small)
2. Dinosaurs
3. Fern forest
B. Jurassic period
1. Dinosaurs
2. Modern birds evolved from birds of this period

17. End of the Mesozoic C. Cretaceous Period 1. New Mammals
2. Flowering Plants
D. Mass extinction of the dinosaurs
1. 66% of all living species extinct
2. Evidence of meteorite collision (Mexico)
E. Pangaea broke apart
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66% died
34% survived

18. End of the Mesozoic
See “Owen’s Dinosaur Video”
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19. X. The Cenozoic Era 66 MYA – present
A. Mammals flourish
B. 30 MYA- primates
C. 200,000 years ago, modern humans