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Our solar system was a swirling mass of gas and dust. Most of the material was pulled together by the gravity of the sun. The remaining dust, gas, and debris circled the sun.
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Earth grew larger, as gravity pulled in more debris, The debris became compact and formed planets. The collision between the earth and debris also created thermal energy. This energy would have been enough to melt parts of the earth.
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Scientists are able to determine the age of the earth by studying the layers of it, and the sedimentary rock.
At this point, Earths atmosphere lacks oxygen. Also, cells arise as molecular systems become enveloped by membranes. -
Forms of life become photosynthetic, in order to be able to survive, by producing oxygen, Cells begin to interact, and stromatolites formed. These are important, because they lead to later developments that were crucial to our existence.
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Respiration developed in mitochondria of cells. We need mitochondria in our bodies, to help with cellular respiration.
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Volcanoes emitting gasses covered the planet, which caused the earth’s atmosphere to have a lack of oxygen.
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At this point, the O2 levels reached today’s levels. Nuclei also formed within cells. Evidence of endosymbiosis can be seen.
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There was a rapid rise in atmospheric oxygen. Cells also began to collaborate, and prokaryotes & eukaryotes were created!
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The ozone (O3) was formed, which protected organisms from harmful UV rays. This allowed them to exist on land. This is also when photosynthesis on land (eg. plants) had started, and the beginning of the cryogenian ice age.
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In the 1600s -1700s, Redi discovered that maggots started to appear on meat exposed to flies. Also, the first microscope was invented, allowing scientist to look at things that they originally couldn’t see with the naked eye.
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Between 1700 and 1800, Spallanzani proved that microorganisms could carry through the air, therefore cancelling the idea of spontaneous regeneration.
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Pasteur proved, between 1800 and 1900, that like Spallazani, that microorganisms carried through the air. He discovered that it was not by spontaneous generation.
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Also, Sidney Fox studied physical structures that may have given rise to the first cells, and provide research on microspheres and coacervates. Finally, Lynn Margulis came up with the theory on the origin of eukaryotic cells, & the endosymbiotic theory (generally accepted for how organelles were formed).
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Around this time, scientists started to use radiometric dating: a process used to date material based on a comparison between the observed abundance of a naturally occurring radioactive isotope & its decay product. Thomas Cech discovered RNA can act as a catalyst. Urey & Miller tested the occurrence of chemical origins of life. Oparin hypothesized that the evolution of life came about through the raw materials present during Earth's early life.
