CHAPTER 11.1
Responses to Change
Developing a Geologic Time Line
Precambrian Life
The time scale and fossils
Major divisions in the geologic time scale
Units in the geologic time scale
Eneons are the longest units of geologic time.
Eons are subdivide into smaller units of time called Eras
Eras are subdivided into Periods.
Periods are subdivided into Epochs
When geologist began developing the time scale, they chose the time boundaries based on what they observed in Earth rock layers.
While studying the fossils in rock layers, saw abrupt changes in the types of fossil within the layers.
A mass extinction is the extinction of many species on Earth within a short period of time.
Changes in climate
Geography and Evolution
All species of organism depends on the environment in their survival.
Land Bridges
Geographic Isolation
A Land Bridge connects to continents that were previously separated.
Geographic Isolation is a separation of a population of organisms from the rest of its species due to some physical barrier, such as a mountain range or a ocean.
Precambrian Life
Cambrian Explosion
Some Cambrian life-forms such as trilobites were the firsts to have hard body-parts.
Many species became extinct at the end of the Precambrian.