1. G EOLOGIC T IME S CALE Chapter 30

2. D IVISION OF G EOLOGIC T IME Geologic Time Scale: a summary of major events in Earth’s that are preserved in the in the rock record. Divided into four sub-categories. Eons Eras Periods Epochs

4. D IVISION OF G EOLOGIC T IME Eon: longest segment of geologic time. Archean (4bya) – Oldest/formation of Earth’s crust. Proterozoic(2.5bya)- oldest fossils of simple ocean life. Phanerozoic(543mya) – signs of visible life.

5. D IVISION OF G EOLOGIC T IME Phanerozoic Eon is subdivided into three ERAS : Paleozoic (543mya) – fossils of ocean and land plants and animals (age of invertebrates). Mesozoic (248mya) – Dinosaurs(age of reptiles) Cenozoic (~65mya) – Last ice age and the (age of mammals) appearance of humans in the fossil record. Eras are divided into periods and periods into epochs.

6. C HANGES THROUGH G EOLOGIC T IME The Earth has undergone many changes through history. Addition of O2 from mostly Co2, SO, intro of life, mountain/ocean formation…

7. E VOLUTION What is evolution? It is the process of change that introduces new life forms. The mechanism in which this happened is called natural selection. This concept was introduced by Charles Darwin, a naturalist.

9. E VOLUTION. What is natural selection? It’s the process by which organisms best suited to their environmental conditions are most likely to survive and reproduce.

10. K ETTLEWELL ’ S R ESEARCH