1. Chapter 15:5
Geologic Time Scale

2. Geologic Time Scale
Divides Earth’s 4.6 billion year history into parts
Our division of time:
Day  Hour  Minute  Second
Division in Geologic Time Scale:
Eon  Era  Period  Epoch

3. Extinction Means death of every member of a species
Most paleontologists agree on five mass extinction events in Earth’s history, but they do not agree on the cause of those events

4. Precambrian Era
Lasted from 4.6 billion years ago to 543 million years ago
First signs of life are bacteria in the water
By end of this era, animals such as jellyfish and worms have appeared

5. Paleozoic Era
Lasted from 543 million years ago to 248 million years ago
First era we find fossils from
By the middle of the era, we started to see plants on land
By the end of the era, amphibians and reptiles lived on land and there were many insects
Ended with largest mass extinction in Earth’s history (killed about 90% of species)

6. Mesozoic Era Lasted from 248 million years ago to 65 million years ago
Known as the Age of the Reptiles because they dominated
Divided into Triassic, Jurassic, and Cretaceous Periods

7. Mesozoic Era continued
Triassic Period – Mammals appear and the first dinosaurs are appearing
Jurassic Period – The Age of the Dinosaur begins and birds begin to appear towards the end
Cretaceous Period – Dinosaurs dominate, T-Rex and Triceratops roam the Earth, but all dinosaurs will have died out by the end.

8. Cenozoic Era Lasted from 65 million years ago to the present
Known as the Age of Mammals
Divided into Tertiary and Quaternary Periods

9. Cenozoic Era continued
Tertiary Period- Mild climate, it is believed that humanlike creatures began walking upright toward the end of this period
Quaternary Period- climate turns very cold, last ice age ends about 11,000 years ago, and modern civilization begins