1. Earth History - The Geologic Time Scale

2. The Age of the Earth
4.6 billion years old =
4,600,000,000

3. The earth’s 4.6 billion year history is divided into major units of time:
Precambrian Time
Paleozoic Era
Mesozoic Era
Cenozoic Era

4. Precambrian Time
4.6 billion years before present to 544 million years before present
Longest era with a sparse fossil record
Origin of earth’s crust, first atmosphere, and first seas
Earliest fossils of cyanobacteria use photosynthesis to produce oxygen
Ozone layer in the atmosphere is formed from oxygen

5. Paleozoic era
544 million years before present to 245 million years before present
Marine communities flourish
Early fishes develop
Origin of amphibians, insects & reptiles
Recurring ice ages/ Appalachians mountains form
Spore-bearing plants dominate .

6. Paleozoic era (continued)…
million years before present: Supercontinent of Pangea forms
248 million years before present: MASS EXTINCTION-90 % of all known families lost! c .

7. Mesozoic Era
245 million years before present million years before present
The age of the dinosaurs!
Gymnosperms dominate land plant/ origin of angiosperms - flowering plants
Origin of mammals & birds
145 million years before present - asteroid impact? MASS EXTINCTION
Pangea begins to separate/ Rocky mountains form

8. 65 million years before present….
ASTEROID IMPACT!
Mass extinction of ALL dinosaurs and many marine organisms
End of the Mesozoic era .

9. Cenozoic Era 65 million years before present - today
Present era we live in
Continued evolution and adaptations of flowering plants, insects, birds, mammals
Mammals dominant
Major crustal movements & mountain building (Alps & Himalayan mountains form) .

10. And during the Cenozoic era…
The most primitive hominid (human ancestor) evolves - approximately 4.4million years before present
The first modern humans (homo sapiens) evolved approximately 100,000 years before present
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12. Assignment – You can use your Textbook and your cell Phones
Describe the Experiments of Louis Pasteur and Alexander Oparin and Stanley Miller in relation to Formation of First Cells on Earth.
Bacteria were the first living cells on earth. How did Eukaryotic or Multicellular organisms came into being. Describe Endosymbiosis.