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The solar system was beginning to form as a swirling mass of gas and dust. This gas and dust formed the sun.
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The Earth began to form and grow by the collisions of debris in space. Later, volcanoes on the Earth emitted gas and formed the atmosphere.
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Organic molecules were beginning to form. Also, a cellular organism similar to Archaea began appearing as the first organism to populate the Earth.
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Fossils of stromatolites were found. Also, the early steps of aerobic respiration began to form. During this time, oxygen was damaging to early unicellular organisms, but it was harmless when bonded to other compounds.
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Forms of life became photosynthetic at this time. Cyanobacteria formed as well.
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The Earth at this time looked similar to the Earth today.
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Oxygen levels reached today's levels.
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A type of small, aerobic prokaryote began to live and reproduce inside larger, anaerobic prokaryotes. Eukaryotes provided a beneficial environment. Prokaryotes provided a method of energy synthesis, called endosymbiosis.
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The ozone (O3) formed. It protected organisms from harmful UV rays so they could exist on land.
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Scientists started using microscope which helped them discover and observe microorganisms.
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He put meat in jars, but only sealed half of them. Later, he noticed that the sealed jars had no maggots, but the unsealed had maggots. The flies were able to fly into the unsealed jars and lay their eggs in the meat. This showed that organisms come from other organisms.
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Spallanzani boiled chicken broth in beakers and sealed half of them immediately after he was done boiling them. He noticed that the unsealed beakers became brown and cloudy over time, whereas the sealed beakers stayed the clear yellow color.
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Louis Pasteur redesigned Spallanzani's experiment with flasks with curved necks. His successful experiment proved that contamination was from microorganisms in the air.
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In the early 1900's, Sidney Fox did research on mircospheres and coacervates. These organisms were believes to have given rise to the first cells on Earth.
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In the 1920's, scientists Oparin & Haldane proposed the hypothesis that the early Earth's atmosphere was comprised of ammonia, hydrogen gas, water vapor, and methane.
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In the 1930's, Lynn Margulis proposed the idea that aerobic prokaryotic cells developed good relationships inside of anaerobic prokaryotic cells. This process is called endosymbiosis.
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A method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope.
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Scientists Miller & Urey performed an experiment with the gases believed to be in the early Earth's atmosphere. They sent electric currents through these gases and after a few days, the gases had formed amino acids.
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In 1980, Thomas Cech found that some types of RNA can act as a chemical catalyst called ribozymes. These ribozymes could have helped form the first replicating cells.
