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(5 BYA) Formation of the solar system/sun
The Solar system was a swirling mass of gas and dust. Over time, the sun was formed by gravity pulling together these materials. Planets also formed through collisions of space debris. -
(4.6 BYA) Formation of the Earth
The Earth began to form and continued to grow by colliding with space debris. The collisions between Earth and Space released a high amount of thermal energy. -
(4 BYA) Organic Molecules
The oldest known rocks and crystals are 4 billion years old. Scientists infer that these organic molecules began to accumulate then. They formed this inference by using radiometric dating. -
(4 BYA) Archaea/ cellular life
Archaea are thought to be similar to the types of cellular life that first populated the earth 4 BYA. -
(3.5 BYA) Stromatolite Fossils
Fossils of stromatolites as old as 3.5 billion years are known. -
(3 BYA) Photosynthetic Life
Some forms of life had become photosynthetic. This was inferred by scientists through different geological events, including chemcial traces of photosynthetic activity. -
(2.2 BYA) Earth's Appearance
Earth appeared like it does today -
(2 BYA) Oxygen Levels
Oxygen levels reached today's levels. -
(2 BYA-1.5 BYA) Endosymbiosis Theory
The first forms of endosymbiotic life existed 1-1.5 BYA. This occured when a mall aerobic prokaryote was engulfed by and began to live and reproduce inside of a larger anaerobic prokaryote -
(1 BYA) Ozone layer formation
Ozone (O3) formed, which protected organisms from harmful UV rays, allowing them to exist on land -
Hooke and early microscope discovery
Hooke used the first light microscopes, which used optical lenses to magnify objects by bending light rays to observe cork and saw cells. -
Redi's Experiment
Francesco Redi's experiment had net-covered jars and uncovered jars filled with meat. Maggots were not found in the net-covered jars. However they were found in the uncovered jars within days, because that was the only place where adult flies could reach the meat to lay the eggs. -
Spallanzani's Experiment
Lazarro Spallanzani showed that microorganisms would not grow in broth when its container was heated and then sealed. However, microorganisms did grow in the unsealed container. He inferred that microorganism dont arise spontaneously but are carried in the air. -
Pasteur's Experiment
Louis Pasteur used a variation of Spallanzani’s design and proved that microorganisms are carred in the air an don’t arise by spontaneous generation. -
Radiometric Dating
Radiometric dating is a method of establishing the age of materials by using their radioactive decay rate, also known as a half-life. Scientists can date materials all the way back to 4 billion years ago by using this effective method. -
Oparin's Hypothesis
Oparin’s hypothesis: early atmosphere contained ammonia, hydrogen gas, water vapor, and hydrogen carbon compounds and at high temperatures, these gases could form simple organic compounds. -
Urey and Miller
Urey and Miller tested Oparin’s hypothesis and produced a variety of organic compounds, including amino acids. -
Sidney Fox
Sidney Fox researched physical structures that gave rise to the first cells, such as microspheres and coacervates. -
Lynn Margulis
Lynn Margulis developed the endosymbiosis theory to explain how eukaryotes first formed. -
Thomas Cech
Thomas Cech discovered a type of RNA found in some unicellular eukaryotes that is able to act as a chemical catalyst. He used the term ribozyme to describe an RNA molecule that can act as a catalyst and promote a specific chemical reaction.
