1. Geologic Timescale and Eras
Notes Ms.Colvin
Page 31 in notebook

2. Personal Timeline
Create a “timeline” of your life that includes major life events.
Start with your birth year and work toward the present
Any event that you feel was large or had a major impact on you will work!
Example: A life event could be starting kindergarten OR the birth of a sibling

3. Discussion Questions:
Discuss the following with your group AND have 1 person write best responses on blank paper given. All names of group go on the paper
Why did you pick the events that you did?
What events do you think you would add in the future?
How do you think your timeline would differ from a Scientific timeline on Earth’s history? What would be similar?

4. Timelines
Your timeline covers the history of your life thus far and spans from years
Earth history is measured with a timeline as well… called the Geologic timescale.. It is MUCH longer than yours but is also separated by major events

5. Geologic timescale is…
a record of the major events and diversity of life forms present in Earth’s history.
Starts at Earth’s formation and goes on to present day

6. Eras The geologic timescale is divided into Eras
Eras are: long distinct periods of time in history; marked by major event or feature

7. 4 major eras There are 4 major eras in Earth’s biological history
Each era ended with a mass extinction and each era had common organism types
Scientists have been able to define these eras and their lifeforms using fossils

8. Precambrian Era 1st era of time
Began with “life” of bacteria and simple algae
Eventually simple sea life formed (like jellyfish and sea worm)
Very few fossils for this time period, because most organisms were soft bodied

9. Paleozoic era First organisms were invertebrate
1st era with fish with vertebrate, insects, amphibians
At end of era, 1st simple reptiles
Mosses and ferns were first land plants
Ended in mass extinction

10. Mesozoic era Reptiles were dominant (age of dinosaurs)
1st mammals and birds appeared
1st flowering plants appeared
Mass extinction at end of era killed off all dinosaurs

11. Cenozoic era New mammals appeared (age of mammals)
Flowerings plants most common
1st humans appeared
Most complex and diverse life forms

12. Fossil record
Collection of millions of fossils that have been studied to create geologic timescale
gives important information about past life and environments on Earth
Shows us estimate of when major extinctions happened