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(5 BYA) Solar System Began Forming
Swirling mass of gas and dust pulled together by gravity came together to form the sun. -
Period: to
2 Sterner Whitcraft History of Earth Timeline
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(4.6 BYA) Earth Began Forming
Dust and debris circling the sun collided because of gravity and grew larger, forming the Earth. -
(4 BYA) Organic Molecules Began Forming
Molecules were formed because the energy from lightning and ultraviolet radiation started the chemical reactions, which led to the formation of the organic molecules. -
(4 BYA) First Cellular Life on Earth
The archaic species Methanosarcina barkeri,which produces methane during metabolism, were similar to the types of cellular life that first populated the earth. -
(3.5 BYA) Stromatolites Existed
Fossils of Stromatolites, a form of cyanobacteria that forms large colonies and grow in layers, were found from 3.5 BYA. -
(3 BYA) The First Photosynthesis
Forms of life first became photosynthetic. Scientists believe that some of the oldest fossils of cells are similar to modern cyanobacteria, which is photosynthetic. -
(2.2 BYA) Earth Modernizes
Earth appears similar to what it is today. -
(2 BYA) Oxygen Becomes Prevalent
Oxygen levels reach what they are today. -
(1.5 BYA) Creation of Eukaryotes
Small aerobic prokaryotes were engulfed by large anaerobic prokaryotes, creating the eukaryote, by endosymbiosis. -
(1 BYA) Ozone Formed
The ozone formed because the rising O2 was split by wavelengths of sunlight, creating high reactive single oxygen atoms. These atoms reacted with the remaining O2, producing O3, or ozone, which protects organisms from harmful ultraviolet rays allowing them to exist on land. -
(1668) Redi's Experiment
Redi was perplexed as to why maggots appeared where flies had landed. This led to him questioning his previously held thought that flies came out of the air spontaneously. So, he did an experiment with rotting meat which showed that flies come from eggs laid by flies. -
(Mid 1800s) Pasteur's Experiment
This experiment was almost exactly like Spallanzani's except Pasteur used a curved neck flask, which did not let microorganisms enter the flask. During this experiment Pasteur boiled broth in a curved neck flask and he let it sit for a year. In the curved neck part of the flask microorganisms had built up. After a year Pasteur removed the curved neck and after a day the broth became contaminated. This led to more people believing in biogenesis. -
(1950s) Radiometric Dating is Perfected
Radiometric dating is a method of determining the age of specific material, using the proportion of radioactive isotopes in the sample. These radioactive isotopes undergo radioactive decay at the rate of the substance's half life. By using the ratio of radioactive isotopes still left in the sample, it is possible to calculate the age of the sample. -
(1960s) Sidney Fox's Discovery
Microspheres and coacervates were produced in a laboratory from simple organic chemicals. These cell-like structures can grow/bud. They also have the ability to take up substances from its surroundings, however, they carry no hereditary information. This reveals a smaller gap between cell life and nonliving chemical compounds. -
(1966) Lynn Margulis Proposes Endosymbiosis
Endosymbiosis suggests that a small, aerobic prokaryote was engulfed by a large, anaerobic prokaryote, creating the eukaryote. It is believed that these small aerobic prokaryotes turned into mitochondria, which perform the respiration in an eukaryotic cell. Photosynthetic cyanobacteria may have evolved into chloroplasts, which carry out photosynthesis in eukaryotic plant cells. -
(1980s) Thomas Cech Discovers Ribozymes
Cech found a type of RNA in single celled eukaryotes that can act as a catalyst and promote a chemical reaction, which he called a ribozyme. This led to more studies following Cech's research that found that ribozymes could act as catalysts to their own replication. This supports the hypothesis that life started from self replicating pieces of RNA. -
(1665) First Microscope Used
Right before Redi's experimentm, other scientists were using the first microscope and saw that the world contained many microorganisms. The scientists found out that there are many microorganisms and that their structure is fairly simple. Some of these scientists concluded that microorganisms come out of the air. -
(1920s) Oparin's Hypothesis
Oparin and Haldane thought that Earth's early atmosphere contained ammonia, hydrogen gas, water vapor, and compounds made of carbon and hydrogen. Oparin thought that under high temperatures these compounds might form organic compounds. When the Earth cooled and the water vapor formed the lakes and seas, these organic compounds settled in the water. Then lightning and UV radiation were used to start chemical reactions, that led to the formation of macromolecules, which are needed for life. -
(1953) Urey and Miller's Experiment
Stanley L. Miller and Harold C. Urey saw that Oparin has a hypothesis, but there was no experiment ever done to support or unsupport it. They set up an experiment to test his hypothesis, using the gases Oparin thought were present in the atmosphere, and electric sparks to replace lightning. The experiment was a success, as it produced several organic compounds that are vital to life, such as amino acids. -
(1700s) Spallanzani's Experiment
This was another experiment which was based on proving whether or not spontaneous generation existed. Spallanani hypothesized that microorganisms come from other microorganisms. In this experiment Spallanzani boiled broth in flasks. He covered one of the flasks. He let them sit for a couple of days and after those couple of days, the covered broth was still clear, but the uncovered one was not clear. He then concluded that boiled broth became contaminated. because it was introduced to air
