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Creation of sun and solar system
The sun was created by a swirling mass of gas and dust. The debris circled into the beginnings of the sun. The remaining debris formed planets through collisions of the debris. -
Earth Formed
The Earth was formed through gravity pulling in debris. There were collisions between Earth and the debris in space which caused thermal energy. Some of these collisions caused enough thermal energy to melt large portions of Earth's surface. -
Earth's Layers
Earth had many layers of sedimentary rock. Scientists attempt to determine what happened so long ago based on these layers. Oldest known rocks and crystals were dated back to 4 billion years ago. Scientists also predict that there were organic molecules that began to accumulate during this time period. -
Stromatolites
Layered structures, stromatolites, were discovered through fossils dating back to 3.5 billion years. -
Photosynthetic Life
Some forms of photosynthetic life began, based on the fossils found. -
Earth's Appearence
Earth probably appeared similar to earth now. -
Oxygen Levels
Oxygen levels reached today’s levels. -
Early Eukaryotes
A small aerobic prokaryote was engulfed by and began living and reproducing in a large anaerobic prokaryote, now known as a eukaryote. The first eukaryotes were living between 2 BYA and 1.5 BYA. -
Ozone
Ozone (O3) formed which protected organisms from harmful UV rays so they could exist on land. The ozone formed from O atoms reacting with O2 atoms. Although the ozone is poisonous to both plants and animals, the layer in the upper atmosphere absorbs much of the UV rays from the sun. -
Early Microscope
The use of the first microscope in 1665, used by both Robert Hooke and scientists in the 17th century, allowed discoveries about microorganisms -
Francesco Redi
Francesco Redi conducted an experiment in 1688 to test that meat kept away from adult flies would remain free of maggots, because the isolated flies would not be able to lay eggs on the meat. His results showed that flies only come from eggs laid by other flies. -
Lazzaro Spallanzani
Lazzaro Spallanzani (1729-1799) tested his hypothesis that microorganisms form from other microorganisms, not air. His experiment used meat broth in sealed and unsealed flasks to prove his hypothesis correct. -
Louis Pasteur
Louis Pasteur (1822-1895) conducted an experiment showing that microorganisms are in the air. He used a flask with a curved and open neck, which prevented microorganisms from entering. When the curved neck was removed microorganisms entered the flask. His experiment is significant because it cleared up issues about spontaneous generation. His results became a cornerstone in biology. -
Oparin's Hypothesis
In the 1920s Alexander I. Oparin (1894-1980) hypothesized that the early atmosphere contained gases that formed simple organic compounds such as amino acids, due to high temperatures which formed the gases. -
Miller-Urey experiment
In 1953 the Miller-Urey experiment tested the conditions for formation of organic molecules on the early Earth, which was based off Oparin’s hypothesis. -
Sidney Fox
Sidney Fox (1912-1998) researched about physical structures, like microspheres and coacervates, that may have supported the first cells. -
Thomas Cech
In the 1980s Thomas Cech (1947- ) discovered a type of RNA found in some unicellular eukaryotes that is able to act as a chemical catalyst. This term is also known as a ribozyme -
Lynn Margulis
Lynn Margulis (1938- ) proposed that prokaryotic cells had a mutually beneficial relationship in the evolution of eukaryotic cells. Her proposition contributed to the endosymbiosis theory -
Radiometric Dating
Radiometric dating (1900-present) is a technique that is established to determine the age of materials. The absolute age is determined by comparing the relative percentages of a radioactive isotope and a stable isotope.
