EARTH ’ S HISTORY NOTES

1. EARTH’S HISTORY NOTES • Scientists believe the Earth and the other planets formed while the Sun condensed from a nebula Origin of Planet Earth

2. Formation of Earth’s layered structure • As Earth formed • High-velocity impacts caused Earth’s temps to increase • Iron and nickel sinks towards the core • Less dense masses of molten rock produced primitive crust • A early atmosphere was made mostly of CO2

3. Life evolves • Earth Cools and oceans form • Bacteria evolve 3.7 BYA Cyanobacteria produce oxygen for billions of years! • CO2 in the atmosphere is almost completely removed and the amount of oxygen rises.

4. Geologic Time Scaleis a “calendar” of Earth history that divides geologic history into units • Originally created using relative dates • Eon– the largest expanses of time • Era – subdivision of an eon • Periods – Subdivisions of eras • Epochs – are the smallest timespans (not to be confused with ewolks!)

5. Precambrian era (4.5 BYA - 540 MYA) • 88% of Earth's history • Precambrian rocks contain extensive iron ore deposits but no fossil fuelsand few fossils • (StromatolitesAppear 2 BYA)

6. Paleozoic era (540-248 MYA) • Often called the time of fish although true fish developed late in this period. • First life forms Multi-cellular life forms with hard parts formed abundant Paleozoic fossils.

7. Paleozoic era • In the Early Paleozoic life was restricted to seas, invertebrates such as • Trilobites • Brachiopods • Cephalopods • First organisms with hard parts, such as shells - perhaps for protection

8. Late Paleozoic era • Supercontinent of Pangaea forms causing dramatic climate shift

9. Late Paleozoic • First land plantsgrow extensive swamps forming coal • Insects invade the land • Fishes evolve into two groups of bony fish • Lung fish • Lobe-finned fish which evolve into the 1st amphibians • Amphibians diversify

10. Paleozoic is believed to end as a result of enormous volcanic eruptions in what is now Russia. These events poisoned the sea and air and lead to the extinction of 95% of species!

11. Mesozoic era (248-65 MYA) • Survivors of the great Paleozoic extinction evolve and diversity. • Gymnosperms(Conifers and ferns) become the dominant tree • Often called the "age of dinosaurs" • Divided into the Triassic, Jurassic and Cretaceous Periods • Seas invade western North America

12. Mesozoic era • Mesozoic life • Divided into the Triassic, Jurassic and Cretaceous Periods • Reptiles - first truly terrestrial animals readily adapt to the dry Mesozoic climate with shell-covered eggs that can be laid on the land. • Mammals exist only as small rodent like creatures.

13. Mesozoic era • Dinosaurs dominate • One group of reptiles led to the birds • Many reptile groups, along with many other animal groups, become extinct at the close of the Mesozoic Most likely the result of a large asteroid or comet struck Earth

14. The Chicxulub Impact Site

15. Cenozoic era (65 MYA-Present) • Shortest era of geologic time • Mammals diversify & replace reptiles as the dominant land animal some groups become very large (Hornless rhinoceros, stood 16 feet high!) • Angiosperms - flowering plants dominate the plant world • Strongly influenced the evolution of both birds and mammals • Provide a food source for both birds and mammals

16. Cenozoic era Human Species Evolves • 2.5 millions years ago Homo habilis – early toolmaker • 200 thousand years ago – Homo sapiens • 50 thousand years ago modern humans and large animals go extinct • 12 thousand years ago development of agriculture and first cities