1. “Theories about the Timeline of Earth” Text pages 44-46

2. Scientific Theory – an explanation of observations, based on facts
All scientists don’t agree
Many theories may be wrong
One theory may be right, parts of all theories may be wrong

3. Theories or beliefs that might explain the development of life on Earth…
Ex. Materials for life arrived on a spacecraft from another
planet!!!!!
Ex. Materials for life
arrived on a meteor!

4. Earth’s Timeline Theory
4.6 BYA –
FORMATION OF EARTH
clouds of debris pull together due to gravity

5. volcanoes are everywhere earthquakes atmosphere is poisonous
4.1 BYA –
FIRST SOLID ROCK FORMS -
solid rocks form
volcanoes are everywhere
earthquakes
atmosphere is poisonous

6. vapor condenses into rain oceans fill
3.9 BYA – RAIN BEGINS –
volcanoes produce water
vapor
vapor condenses into rain
oceans fill

7. 3.6 BYA – ORGANIC SOUP FORMS – early oceans fill with substances needed for life

8. 3.5 BYA – FIRST CELLS FORM – chemicals from “soup” collect into droplets

9. 3.0 BYA – PHOTOSYNTHESIS BEGINS –
oxygen is
produced
in the
atmosphere

10. 2.5 BYA –
PRECAMBRIAN ERA –
first bacteria, jellyfish,
coral, clams

11. 570 MYA – PALEOZOIC ERA – first land plants, fish, insects, reptiles, amphibians

12. 225 MYA – MESOZOIC ERA – cone bearing, and flowering plants, dinosaurs, first birds and mammals

13. 65 MYA – CENOZOIC ERA – modern plants and mammals

14. 53 years ago – UREY/MILLER EXPERIMENT – gases mixed to form
tar-like
substance

15. Stanley Miller working in the lab at the University of Chicago

16. Approximately 13 years ago
You were born