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Earth’s History

Earth’s History. A history including how life evolved, how the geosphere changed and major extinction events. . Time periods. Eons Eras Periods Epochs. Pre- Achean Eon (Hadean Eon): Formation of Earth. Earth is approximately 4.6 billion years old. Remember: How did Earth form?

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Earth’s History

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  1. Earth’s History A history including how life evolved, how the geosphere changed and major extinction events.

  2. Time periods • Eons • Eras • Periods • Epochs

  3. Pre-Achean Eon (Hadean Eon): Formation of Earth • Earth is approximately 4.6 billion years old. • Remember: • How did Earth form? • How are elements arranged? • Earth began to cool • 4 billions years ago: rocks • 3.8 billions years ago: water

  4. The first organic molecules • Could organic molecules form in Early Earth? • Miller and Urey experiment

  5. The puzzle of life’s origin • Geologic evidence suggests that about 200 to 300 million years after earth cooled enough to carry liquid water, cells similar to modern bacteria were common. • How did these cells originate? • Microspheres • Evolution of RNA and DNA

  6. Archean Eon: First organisms • The first organisms were single celled prokaryotic anaerobic cells that resemble modern bacteria. • Evidence: microscopic fossils in rocks that are more than 3.5 billion years old. • Photosynthetic cells! • How did the oceans go from brown to blue-green? What color is the sky now?

  7. Proterozoic Eon: Origin of Eukaryotic cells • Endosymbiotic theory

  8. Proterozoic Eon : What did Earth look like?

  9. Phanerozoic Eon: Diversity • How did live begin to evolve into diverse life? • Asexual versus sexual reproduction • Multicellularity

  10. Paleozoic Era • Periods: • Cambrian: “Cambrian explosion”, hard parts, shells, outer skeletons, invertebrates, arthropods. • Ordovician and Silurian: aquatic arthopods, fishes, first land plants, octopi and squid. • Devonian: land plants, insecnts, vertebrates, sharks, “age of fishes”. • Carboniferous (Mississipian/Pennsylvanian) and Permian: amphibians, reptiles, winged insects, ferns.

  11. Cambrian Period: What did Earth look like?

  12. Ordovician Period: What did Earth Look like?

  13. Ordovician Period • Most organisms lived in the sea at this time. • The sea level dropped caused by plate tectonics. • The majority of land mass was over the south pole at this time and was a large glacier. • Approximately 57% of Earth’s species went extinct at this time.

  14. Silurian Period: What did Earth look like?

  15. Devonian period • The third extinction event occurred at the end of this period. • It was caused by • fluctuating sea levels because more glaciers pulled water from the oceans. • and global cooling due to land plants removing CO2 from the atmosphere. • There was approximately a 50% extinction of the species on Earth.

  16. Permian Period • This is the fourth extinction event. • It is often called the “Great Dying” event and was caused by: • Eruption of Siberian Volcanoes • Formation of Pangaea disrupted ocean currents • Possible meteor impact • This resulted in an 83% extinction event • About 96% of all marine species • About 70% of all land vertebrates • Many arthropods and land plants also died.

  17. Mesozoic Era • Periods: • Triassic: “Age of reptiles”, fishes, insects, cone breaing plants, mammals/ • Jurassic: dinosaurs, birds. • Cretaceous: dinosaurs, birds, leafy trees, shrubs, small flowering plants.

  18. Triassic Period: What did Earth look like?

  19. Triassic period • This is the fifth extinction event • Caused by the eruption of the central Atlantic province. • Sulfur gas blocked the sun • Large amount of lava released over several centuries. • This was a 48% extinction and a majority of the species that went extinct were marine • Ammonites • Corals • Seed ferns

  20. Jurassic Period: What did Earth look like?

  21. Cretaceous Period: What did Earth look like?

  22. Cretaceous Period • At the end of the cretaceous period there was a sixth mass extinction event. • It is often referred to as the “K-T Boundary” and was likely caused by • Pangaea breaking up, • Eruption of Deccan Volcanoes in India • And possibly an asteroid impact. • It marks the end of the cretaceous period/Mesozoic era, the “age of reptiles” (dinosaurs).

  23. Cenozoic Era • Periods: • Tertiary: marine mammals, grasses, large mammals • Quarternary: humans

  24. Quaternary Period: What Earth looks like today.

  25. Quaternary Period • 73,000 years ago there was an event that led humans to near extinction. • It was caused by the Toba super volcano on the island of Sumatra. It disrupted ecosystems on a global scale. • Only a few ‘pockets’ of individuals remained, estimated at around 10,000 total.

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