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• Precambrian


  Life on Earth started more than 550 million years ago, covering approximately 88% of Earth's history, from the planet's creation about 4.5 billion years ago to the emergence of complex, multi-celled organisms almost four billion years later
• Precambrian life


  • Hadean Eon: Earth's initial formation and stabilization of core, crust, atmosphere and oceans
  • Archean Eon: Earth cooled down from molten state, supported oceans and continents, oxygen filled oceans from cyanobacteria, ozone layer formed
  • Proterozoic Eon: Oxygen crisis for anaerobic cyanobacteria, snowball Earth, emergence of eukaryotes and multicellular organisms
• Phanerozoic Eon


  Current geologic eon, began with Cambrian Period when animals first developed hard shells preserved in fossil record
• Paleozoic Era


  • Cambrian explosion brings new life, age of invertebrates, fish and amphibians, rainforest collapsed and buried as coal deposits, Permian-Triassic Extinction
• Mesozoic Era


  • Age of reptiles, dinosaurs and conifers, first birds, mammals and flowering plants, Pangaea started to separate into modern land configuration, dinosaurs went extinct at start of Cenozoic Era
• Cenozoic Era


  • Cretaceous–Paleogene extinction event wiped out dinosaurs, mammals diversified and grew larger, shift from four legs to two, stone age period and modern humans, from human evolution to bustling cities
• Geological Time Periods


  • Cambrian (542-488 MYA)
  • Ordovician (488-444 MYA)
  • Silurian (444-416 MYA)
  • Devonian (416-359 MYA)
  • Carboniferous (359-299 MYA)
  • Permian (299-251 MYA)
  • Triassic (251-199 MYA)
  • Jurassic (199-145 MYA)
  • Cretaceous (145-65 MYA)
  • Paleogene (66-23 MYA)
  • Neogene (23-5 MYA)
  • Quaternary (4 MYA-present)
• The Precambrian life, composed of the Hadean, Archean, and Proterozoic Eras, started more than 550 million years ago and covers approximately 88% of the Earth's history
• The Earth become more conducive to life and allowed single-celled cyanobacteria to exist during the Precambrian
• The earliest life comprising Precambrian biota was long believed to include only tiny, sessile, soft bodied sea creatures, but fossils of sponge-like creatures named Coronacollina acula have recently been discovered in South Australia
• The Hadean Eon is characterized by Earth's initial formation, the stabilization of its core and crust, and the development of its atmosphere and oceans
• Around 45 million years after the planets first began to form, the Moon formed, probably from a large planetoid about the size of Mars (Theia) crashing into the Earth
• In the Archean Eon, Earth finally starts to cool down from its molten state, allowing oceans and continents to form, oxygen to fill the oceans from cyanobacteria, and the ozone layer to develop
• The Proterozoic Eon saw an oxygen crisis for anaerobic cyanobacteria, a "snowball Earth" from an oxygen-filled atmosphere, and the emergence of eukaryotes and multicellular organisms
• The Phanerozoic Eon began with the Cambrian Period when animals first developed hard shells preserved in the fossil record
• The Paleozoic Era saw the Cambrian explosion bringing new life, the age of invertebrates, fish and amphibians, the collapse of rainforests buried as coal deposits, and the Permian-Triassic Extinction
• The Mesozoic Era was the age of reptiles, dinosaurs and conifers, but also saw the first birds, mammals and flowering plants, as well as the separation of the supercontinent Pangaea
• The Cenozoic Era saw the Cretaceous–Paleogene extinction event wipe out the dinosaurs, allowing mammals to diversify and grow larger, the shift from four legs to two, the stone age period and the rise of modern humans