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(5 BYA) Solar System
The solar system was a swirl of gas and dust because it was just starting to form. The dust came closer and closer together, until it formed the sun. The sun is essential for life on Earth. The remaining dust also formed the planets around the sun. -
(4.6 BYA) Earth
Over time, the debris and dust started to form the Earth. It progressively grew larger as it collided with these particles. These collisions produced thermal energy, which melted the Earth’s crust. This gave the Earth the shape it has today. -
(4 BYA) Archea
The archaeal species, Methanosarcina barkeri was found to produce methane during metabolism. Archea similar to these types of cellular life, populated earth 4 BYA -
(4 BYA) Planet Earth
It is estimated through looking at the different geologic layers, that this is Earth’s age. It wasn’t clear if this was true until radiometric dating allowed scientists to predict it accurately. It allowed scientists to look at the organisms in the different layers of sedimentary rock, and estimating their age. -
(4 BYA) Oldest Rocks and Crystals
The oldest rocks and crystals are estimated to be 4 billion years old. Scientists used radiometric dating to get this estimate. They also inferred that, because of this fact, organic molecules had to start accumulating at around this time. -
(3.5 BYA) Fossils
Fossils of stromatolites are found. They are similar to cyanobacteria. -
(2.2 BYA) Earths appearance
Earth probably looked like it does today. This was when the atmosphere, oceans, and land fully formed to look like they do today. This was extremely important, because these were the conditions necessary for life to start on this planet. -
(2 BYA) Oxygen
O2 levels reached today’s levels -
(1.5 BYA) Prokaryotes
It was found that a small type of aerobic prokaryote was engulfed by and began to live and reproduce inside of a larger anaerobic prokaryote. -
(1 BYA) Ozone
Ozone (O3) formed- protected organisms from harmful UV rays so they could exist on land -
(1665) Hooke
In 1665 the scientist Hooke used a light microscope, one that bends light rays to magnify the sample, to study cells for the first time. He looked at cork cells and compared them with other plants, and came up with the idea that the cells looked like “little boxes.” This was the first time anyone observed cells and determined a shape for them. Hooke pioneered the study of cells by microscope. -
(1673) Leeuwenhoek
Leeuwenhoek made microscopes, with precisely ground lenses that could magnify 10 times more than Hooke’s microscopes, in 1673. He was able to see microorganisms, such as algae and protist, in clear detail. This was the first time anybody observed cells in such detail. He observed previously unknown organisms, and came up with observations that would lead to the formation of cell theory. -
(1700-1800) Spallanzani’s experiment
Spallanzani’s experiment showed that microorganisms do not arise spontaneously they are carried through the air. Since his experiment boiled broth in flasks to see which one would stay clear, open or closed. This also supported the biogenisis theory. -
(1800-1900) Pasteur’s Experiment
Pasteur’s Experiment took what Spallanzani was doing but changed the design to rebut some critics of the "vital force". He once again proved there was no vital force. -
(1900's) Redi's Experiment
Redi experiment found that rotting meat kept away from flies would not produce new flies and that maggots appeared only on meat that was exposed to flies. This experiment supports the biogenesis theory. -
(1900's) Thomas Cech
Thomas Cech found that RNA is able to act as a chemical catalyst. He found that RNA can also self replicate.Thomas Cech used the term ribozym to describe the RNA that acts as a catalyst. -
(1900's) Lynn Margulis
Lynn Margulis proposed that early prokaryotic cells may have developed a mutually beneficial relationship. Lynn Margulis helped to develope the term endosymbiosis, large prokaryotic engulfed smaller prokaryotic which evolved into mitochondria. -
(1900s) Sidney Fox
Sidney Fox (1912-1998) did extensive research on the physical structures that may have caused cells to appear on Earth. These structures include microspheres, bubbles of same molecules, and coacervates, bubbles of different molecules. This allowed him to gather more information on how these structures fit into the early stages of life on Earth. These structures are molecules that are essential to life combined in large clusters that have the potential to form life-forms. -
(1900s) Radiometric Dating
Radiometric dating, the technique of looking at radioactive elements within the thing being tested, started to be used at around this time to estimate the age of Earth and other materials and organisms on it. This technique looks at the amount of unstable isotopes within the thing that’s being tested, and then estimates its age by looking at the half-life, decay rate, of the unstable isotope. Scientists use carbon-14, as well as uranium, to date materials and organisms. Radiometric dating helped -
(1920s) Oparin and Haldane
During 1920s, scientists Oparin and Haldane proposed that organic molecules could come together at high temperatures to form simple organic compounds, which then could have formed macromolecules essential to life by a complex process triggered by lightning or radiation. Their idea helped link the gap between Earth before life began and Earth after life began, effectively proposing how the conditions of Earth could have started life on Earth. This idea was then tested by Miller and Urey, who prov -
(1953) Miller and Urey
In 1953, a graduate student, Stanley L. Miller, and his professor, Harold C. Urey, did an experiment where they used a chamber containing the gases present in Earth’s atmosphere, according to Oparin, and electric sparks representing lightning that supplied the energy for chemical reactions, to produce organic compounds such as amino acids. They were successful in showing that this could work, effectively supporting Oparin’s theory about what led up to the beginning of life on Earth.
