1. Chapter 10
Geologic Time

2. The Geologic Time Scale
Division of Earth’s history into time units based largely on the types of life-forms that lived only during certain periods
4 Major Subdivisions:
Eons
Eras
Periods
Epochs

3. Subdivisions of Geologic Time
Eon
Longest subdivision in the geologic time scale that is based on the abundance of certain types of fossils
Era
Second-longest division of geologic time
Based on major worldwide changes in types of fossils

4. Subdivisions of Geologic Time
Periods
Units of geologic time characterized by the types of life existing worldwide at the time
Epochs
Next-smaller division of geologic time after the period
Characterized by differences in life-forms that may vary regionally

6. Organic Evolution Change of organisms over geologic time
Environmental changes can affect an organism’s survival
Adapt or die out
Natural Selection
Process by which organisms that are suited to a particular environment are better able to survive and reproduce than organisms that are not
Survival of the Fittest

7. Chapter 10, Section 2
Early Earth History

8. Precambrian Time The longest part of Earth’s history
Includes the Hadean, Archean, and Proterozoic Eons
4.5 billion years ago to 544 million years ago
Cyanobacteria (blue-green algae) is thought to be one of the first living organisms

9. Paleozoic Era Era of ancient life
544 million years ago-248 million years ago
Many marine (ocean-dwelling) fossils have been found during this era
Fossils of both vertebrates and invertebrates have also been found

10. Middle and Recent Earth History
Chapter 10, Section 3
Middle and Recent Earth History

11. The Mesozoic Era Era of middle life
Between 248 and 65 million years ago
Marked by rapid movement of Earth’s plates
Pangaea (massive landmass) began to brake-up and move
Dinosaurs were active during this era
Birds, Mammals, Gymnosperms (produces seeds, but not flowers), and Angiosperms (flowering plants) were also present during this era

12. The Mesozoic Era
Ended with a hypothesized comet or asteroid collision to Earth causing a dust cloud to block out the sun
This resulted in an apparent “great extinction” that killed many of the prehistoric species of living organisms.

13. The Cenozoic Era Era of recent life
Began 65 million years ago and continues today
Divided into the Tertiary and Quaternary periods
Features periods of mountain building