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(5 BYA) Formation of the Sun
Our Solar System was once just a swirling mass of gas and dust until Gravity pulled it all together which formed the Sun -
(4.6 BYA) Formation Of Earth
The Earth started to form in the 400- million year time period after the sun was formed 5BYA. Earth grew larger as more debris was pulled in. A lot of thermal energy was released from collisions between the Earth and space debris. These collisions would be enough to melt portions of the Earth's surface. -
(4 BYA) Fully Formed Earth
Earth was completely formed after 600,000,000 years of space debris colliding with each other. -
(4 BYA) Life forms on Earth
The earliest fossils found on Earth so far are that of an Archael species called Methanosarcina barkeri which produces methane in the metabolism phase of the characteristics of life. -
(3.5 BYA) First Organisms
Fossils of stromatolites are dated back to around 3.5 BYA. They were formed from and found stacked on top of one another. -
(3 BYA) Photsynthetic Life
Some life forms were now known to be photosynthetic such as the Unicellular Prokaryote known as Cyanobacteria. -
(2.2 BYA) Similiar Earth
Earth appears much as it does today. -
(2 BYA) O2 Levels
O2 levels reached today's levels. -
(2-1.5 BYA) Endo-Symbiosis
A small type of an aerobic prokaryote was "swallowed" by an anaerobic prokaryote and reproduced in it. This is called Endo-symbiosis which then later forms into Mitochondria, an essential element in animal/human life. -
(1 BYA) Ozone Formed
Ozone (O3) formwed- protected early organisms from harmful UV rays so they could exist on land. -
(1729-1799) Spallanzani's Experiment
Microscopes were invented and scientists realized that microorganisms were numerous and appeared basically everywhere. They thus concluded that microorganisms arise from a "vital force." To test this, Spallanzani boiled broth in a flask to see whether microorganisms form from other microorganisms. He left one flask open and the other closed. The closed flask remained clear while the open flask became cloudy within a day. People were still not happy with this experiment though. -
(1822-1895) Pasteur's Experiment
Many disregarded Spallanzani's experiment because the "vital force" could not enter the flask. Pasteur changed that by making a flask with a curved neck and boiled the broth in that. He let it sit for a year to prove that the "vital force" in the air wasn't the cause of the broth turning cloudy. It stayed clear for the years' time and one day he broke the neck of the flask. The day after he broke it, the broth became cloudy, proving there was no spontaneous generation. -
(1920's) Oparin's Hypothesis
Soviet Alexander I. Oparin and American John B. S. Haldane thought the early atmosphere had once contained ammonia, hydrogen gas, H2; water vapor, H2O; and compounds made of hydrogen and carbon. Oparin thought that if these elements were exposed to high temperatures they probably would have become simple organic compounds (amino acids). They would then have collected in water when the earth cooled and lakes and seas were formed. The results are macromolecules such as proteins due to reactions. -
(1912-1998) Fox
Fox was the many scientists to study the physical structures that may have become the first cells. These structures include microspheres, which are many protein molecules that form a spherical membrane, and coaservates, which are collections of droplets made up of different types of lipids, amino acids, and sugars. -
(1938- ) Lynn Margulis
Lynn Margulis formed a theory known as endosymbiosis. This theory proposed that early prokaryotic developed mutually beneficial relationships with each other. The theory also states that eukaryotic cells were first formed when small prokaryotic cells were engulfed by larger prokaryotic cells and still survived and multiplied. -
(1947- ) Thomas Cech
In the early 1980s, Thomas Cech discovered a type of RNA found in some unicellular eukaryotes is able to act as a chemical catalyst, which has similar actions to that of an enzyme. He used the term ribozyme to describe an RNA molecule that could act like a catalyst and promote specific reactions. Later studies showed that some ribozymes could act as catalysts for their own reproduction. -
(1953) Urey & Miller
Although Oparin had carefully developed hypotheses, he never did any experiments to prove it. So an American graduate student Stanley L. Miller teamed up with his college Professor Harold C. Urey to test it. They produced amino acids through the gases that Oparin had guessed were in the Atmosphere. This proved the Oparin was right in assuming that the gases were converted to Amino Acids by using sparks (lightning) caused chemical reactions. This was a gateway for many further experiments. -
(Mid-Twentieth century) Radiometric dating
Radiometric dating is a way of establishing the age of materials. Scientists can estimate the age of the earth by using the decay of uranium and thorium isotopes in rock crystals on the Earth. They are the oldest un-melted rock found thus far which means that the Earth probably stopped melting when that rock was formed. The rock had formed 4 billion years ago so scientists can infer that that is when organic molecules began to accumulate on the surface. -
(1665) First MIcroscopes
In the beginning of the 17th century scientist were able to see experiment subject more closely due to the microscope that can magnify objects too small to be seen with the naked eye. THese studies led them to propose the cellular basis of life. The first microscope ever used was the Light microscope in 1665 by Robert Hooke. It uses an optical lens to magnify objects by bending light rays. -
(1668) Redi's Experiment
Redi studied the different developmental stages of flies. He was trying to prove that spontaneous generation of flies from meat was not possible. He put one piece of meat in two flasks. He left one flask open, and the other closed. The closed flask did not contain any flies while the open one did. THis means that spontaneous generation cannot occur in a closed container, or ever.
