-
(5 BYA) Solar System Formation
The solar system was a swirling mass of gas and dust. Overtime, some of this material was pulled toogether by gravity to form the Sun. The remaining material formed the planets through repeated collisions.
The collisions between the space debris released a large amount of thermal energy. -
(4.6 BYA) Earth Formation
The Earth was created through gravitational space debris colliding. This also released thermal energy. Over a 400 million year period, Earth grew larger. -
(4 BYA) First Cellular Life
Archaea are similar to the types of cellular life thatfirst populated Earth. They are unicellular and can survive under harsh conditions. -
(4 BYA) Organic Molecules on Earth
Since the rocks cooled on Earth, organic molecules could accumulate on the surface. Scientists then believed that this was when the collisions and the Earth's surface began to cool. -
(3.5 BYA) Lynbgya Growing in Colonies
Lynbgta, a genus of modern cyanobacteria, grew in colonies called stromatolites. Stromatolites are layered structures made from colonies of Lynbgta. -
(3 BYA) Life Forms Becoming Photosynthetic
Some forms of life nad become photosynthetic by 3 billion years ago. They know this from geologic evidence such as chemical traces of photosynthetic activity. -
(2.2 BYA) Earth Looking Like Today's Earth
Around 2.2 BYA, Earth started looking like it does today. At this time, oxygen gas levels had already reached current levels. Also, the land had cooled and oceans formed. -
(2 BYA) O2 Levels Reach Today's Levels
The oxygen reached the upper part of the atmosphere where it was hit with sunlight. Become of photosynthesis, more O2 was produced and life could be sustained on Earth. -
(2-1.5 BYA) Endosymbiosis Began
Small aerobic prokaryote was enfulged by and began to live and reproduce inside of a larger, anaerobic prokaryote. -
(1 BYA) O3 Formed
The Ozone formed and protected organisms from harmful UV rays so they could exist on land. The sunlight split the 02 into single Os and these Os reacted with O2 to form ozone, which is O3. -
(Aprox. 1665) First Microscopes
Robert Hooke studied nature using an early light microscope. Around this time, scientists becane using microscopes and realized that the world is crawling with microscopic creatures. This helped to discover that microorganisms are simple in structure. -
(1668) Redi Experiment
Redi's experimental group consisted of jars covered in netting that contained meat. The control group consisted of uncovered jars that also contained meat. The netting allowed air to enter and prevented flies from landing on the meat. After a few days, maggots were living in the meat in the open jars, but the jars with no netting did not have any maggots.
This experiment showed that flies come only from eggs laid by other flies. His hypothesis was confirmed. -
(1700s) Spallanzani's Experiment
For his experimental group, Spallanzini boiled clear broth until the flasks filled with steam. While the broth was hot, he sealed the flasks by melting their glass necks. The control-group flasks were left open. The broth in the sealed flasks remained clear and free of microorganisms, while the broth in the open flasks became cloudy because it was contaminated with microorganisms.
Spallanzani concluded that the boiled broth became contaminated only when organisms from the air entered the flask. -
(mid-1800s) Pasteur's Experiment
To answer objections to Spallanzi's experiment, Pasteur made a curve-necked flask that allowed the air inside the flask to mix with the air outside the flask. The curve in the neck of the flask prevented solid particles, such as microorganisms, from entering the body of the flask. The broth boiled inside the experimental curve-necked flasks remained clear for up to a year. But when the curved necks were broken off, the broth became cloudy and contaminated with microorganisms within a day. -
(Early 20th cent.) Radiometric Dating
A method of establishing the age of materials. It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials. -
(1920) Alexander I. Oparin's Hypothesis
He hypothesized that the early atmosphere contained only Ammonia (NH3), Hydrogen (H2), water vapor (H2O), and Hydrogen/Carbon compounds. With the the heating and cooling of these gases, micromolecules could eventually be produced. -
(1953) Urey and Miller
Urey and Miller created an experimental aparatus to test Oparin's hypothesis. They put all of the elements Oparin stated in a chamber, added electrical shocks that simulated lightning, and amino acids were formed along with other organic compounds. -
(early 1980s) Thomas Cech
Cech found that some types of RNA found in some unicellular eukaryotes can act as a chemical catalyst. He called them "Ribozymes." Theu can act as a catalyst and promote a chemical reaction. This led to dicovery that these Ribozymes could replicate themselves and the theory that theu could have been the beginning of life. -
(1912-1998) Sydney Fox
He did extensive research on the physical structures that may have given rise to the first cells (microspheres & coercervates).
