-
(5 BYA) Geologic Event: The Solar System
The soloar system was a swirling mass that collided to form planets and the sun. The collsions between the earth and space debris created a lot of thermal energy. -
(4.6 BYA) Geologic Event: The Earth
The earth was formed in its whole. -
(4 BYA) Gelologic Event: First Molecules
Organic molecules began to accumulate including the oldest known rocks, crystals, and unmelted surface rock. -
(4 BYA) Life Event: Cells
The first cells populated the Earth. -
(3.5 BYA) Life Event: Bacteria
Lynbyga, a form of cyanobacteria, formed colonies. -
(3 BYA) Life Event: Photosynthesis
Certain forms of life become photosynthetic. These life forms were autotrophic, meaning they could make their own food. Heterotrophs could now eat autotrophs because they provided energy. -
(2.2 BYA) Geologic Event: Carbon Dioxide
Carbon dioxide levels reached the average level they are today. This was a milestone because they are about the same now than they were then. -
(2 BYA) Geologic Event: Oxygen
Oxygen levels reached the peak they are today. This is a milestone because the levels are the same now. -
(1.5 BYA) Life Event: Production
A small type of aerobic prokaryote was engulfed by an anaerobic prokaryotic cell. This created a larger cell and was the first time something was "eaten." -
(1 BYA) Geologic Event: Ozone
The ozone layer was formed, becoming a protective shield against UV rays. These UV rays would have destroyed all life on earth if the layer was not there. -
(1673) First Microscope
Anton von Leeuwenhoek produced a very advanced microscope for his time. He was the first person to look at living cells under a microscope. -
(mid-1600s) Redi's Experiment
Francesco Redi, an italian scientist, studied the different developmental forms of flies. He used rotting meat to lure flies to his experiment. Redi proved, in one instance, that biogenesis was how we came to be. -
(mid-1700s) Spallanzani's Experiment
Lazzaro Spallanzani, an Italian scientist, designed an experiment to test spontaneous generation as a hypothesis. He boiled broth and waited for the "vital force" to make life. This experiment was controversial because the closed flask was not letting in the force to create life. -
(1800s) Radiometric Dating
Radiometric dating is a method used to determine the age of materials. This use of radioactive elements to age objects was a milestone because it helped scientists and historians place civilizations and establish time periods. -
(1953) Urey and Miller
Stanley Miller, an American graduate student, and his professor, Harold Urey tested Oparin's hypothesis. This experiment was a milestone in scientific investigation, though the hypothesis is continually being revised. -
(mid-1900s) Fox
Sidney Fox did extensive research on the structures of the first cells. This helped form a general image of what cells really looked like. -
(mid-1800s) Pasteur's Experiment
Louis Pasteur, a French scientist, wanted to prove spontaneous generation wrong. He conducted an experiment including a curved-neck flask that was opened to show that the "vital force" did not exist. At this time, the principles of biogenesis become cornerstone in biology. -
(1920s) Oparin's Hypothesis
Alexander Oparin, a Soviet scientist, and John B. S. Haldane, an American scientist, worked together to form a hypothesis about the early atmosphere. They believed that gases at high temperatures might have created the first organic compunds. When the earth cooled, Oparin hypothesized, the compounds collected in water and went through a series of complex chemical reactions to create essential macromolecules that we have today. -
(mid-1900s) Margulis
Lynn Margulis proposed that early porkaryotic cells could have developed mutually beneficial relationships. This continued to be studied and a model was created to show the engulfing of one cell by another. -
(early 1980s) Cech
Thomas Cech found that a type of RNA in eukaryotic cells could be used as a catalyst. He used the term ribozyme for this molecule. This was the beginning of RNA discoveries around the world.
