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(5 BYA) Sun was formed
The Solar System was a swirling mass of gas and dust that was pulled together by gravity to create the sun. -
(5 BYA) Solar System formed
Remaining gas and debris formed planets through repeated collisions, creating the Solar System. -
(4.6 BYA) Earth Formed
Earth was formed as gravity pulled in debris. Layers of sedimentary rock formed in Earth’s crust, later helping scientists estimate the Earth’s age through the use of radiometric dating: the process of using the radioactive decay of elements. -
(4 BYA) Cellular Life
Methanosarcina barkeri, a type of Archea, are thought to be similar to the first types of cellular life to populate the earth. -
(3.5 BYA) Early Fossils Found
Earliest fossils of stromatolites found. Stromatolites are layers of Lynbgya--a group of photosynthetic, unicellular prokaryotes. -
(3 BYA) Life Forms Found
Some forms of life became photosynthetic (chemical traces of photosynthetic activity). -
(2.2 BYA) Aerobic Repiration
Oxygen bonded with other compounds, showing the first steps of aerobic respiration. This early function was to prevent the destruction of essential organic compounds by oxygen. -
(2 BYA) O2 Levels
O2 levels reached today’s levels. -
(2 BYA-1.5 BYA) First Eukaryotes
A small prokaryote was engulfed by another prokaryote--called endosymbiosis. This new organism was one of the first eukaryotes. -
(1 BYA) Ozone Formed
Ozone (O3) formed – protected organisms from harmful UV rays so they could exist on land. -
1700s-1800s
Jean Baptise Lamarch supported the idea that a population of organisms could change over time. He thought that single organisms could arise from nonliving matter and that they developed into more complex forms. -
1800s-1900s
Louis Pasteur settled the controversy about spontaneous generation when he had a curved beaker to prove that micro-organisms were in the air and not in the broth. After letting both sit (a curved and straight beaker) only the straight becker became cloudy. -
1900s-present
Alexander Oparin believed that the atmosphere contained gases that formed organic compounds that eventually resulted in macromolecules essential to life. Scientists Urey and Miller expanded upon this by testing whether the atmosphere could produce organic compounds by electrifying the elements in a simulation chamber. Thomas Cech found type of RNA in some unicellular eukaryotes is able to act as a chemical catalyst, named them ribozymes. Support hypothesis that life could have started with self- -
1900s-present (2)
-replicating molecules of DNA. Sidney Fox investigated the physical structures leading to the first cells, which then led to the discovery of microspheres and coacervates. Lastly, Lynn Margulis developed the theory of the origin of eukaryotic organelles and the endosymbiotic theory. -
(1600's-1700's)
People believed in spontaneous generation (living things arising from nonliving things). Scientists like Redi (how air venting affects maggot growth on meat), Spallanzani (boiled broth to prove microorganisms come from other microorganisms), and Pasteur all displaced that theory with a new one: biogenesis (all living things come from other living things). In addition, the invention of the microscope allowed scientists to discover all the small, moving organisms within the atmosphere.
