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(5 BYA) Solar System begins
The solar system is born as a swirling cloud of dust. Gravity forms the sun and the rest of the gases swirl around it. -
(4.6 BYA) Earth is born
Colisions between Earth and space debris form the planet Earth which we know today. -
(4 BYA) Oldest known rock and crystals
The oldest known rocks and crystals. Collisions between Earth and large pieces of space debris probably caused the surface of Earth to melt many times as the planet was formed. Therefore, the age of the oldest unmelted surface rock should tell us when the collisions stopped and the cooling of the Earth’s surface began. -
(4BYA) Methane is formed
The archaeal species, Methanosarcina barkaeri, produces methane during metabolism. Archaea are though to be similar to the types of cellular life life that first populated Earth 4 billion years ago. -
(3.5 BYA) Stromatolites emerge
Fossils of stromalites, which are lynbgya cells grown in colonies, are similar to cyanobascteria and are known to be 3.5 billion years old. -
(3 BYA) Forms of Life Becomes Photosynthetic
Due to chemical traces of photosynthetic activity scientists infer that most of the oldest known fossils of cells like this are similar to modern cyanobacteria. -
(2.2 BYA) Modern Earth Appears
After volcanoes emitted gas, earth had formed an atmosphere and by 2.2 billion years ago, it appeared much like it does today. -
(2 BYA) Oxygen Levels Reach Sufficent Amount
Oxygen levels increases to today's levels. -
(1.5 BYA) Endosymbiosis
A type of small aerobic prokaryote was engulfed by, and began to live an reproduce inside of a larger anaerobic prokaryote. -
(1 BYA) Ozone is formed
The oxygen gas eventually reached the upper part of the atmosphere, here it was smothered by sunlight. This layer in the atmosphere, protects organisms from harmful UV rays so they could exist on land. -
Radiometric Dating (Today)
Radiometric Dating- Methods of establishing the age of materials include these techniques. Some isotopes have unstable nuclei, which undergo radioactive decay. The length of time it takes for one-half of any size sample of an isotope to decay to a stable form is called half-life. Isotopes with longer half-lives are used to date rocks, so we know exactly how old earth is. -
Thomas Cech (1980 s)
found that a type of RNA in some unicellular eukaryotes is able to act as a catalyst, like an enzyme. These are known as ribozymes, and are thought to have existed before DNA through several reasons despite its unstabilitiness. -
Sidney Fox (1912-1998)
He has done extensive research on the physical structures that may have given rise to the first cells. These structures included microspheres and coacervates, and may have been the predecessor to the first cell. -
(1920) Oparin's Hypothesis
formed a hypothesis to solve the dilemma of how the organic compounds and all of its elements assembled when the earth was created.
Hypothesis- atmosphere contained ammonia, H-gas, water vapor, and compounds made of H, and C, like methane. According to Oparin, these compounds at high temperatures could form organic compounds such as amino acids(proteins). -
(1700s) Spallanzani's Experiment
His experimental group was a sealed flask while his control group was an open flask. His observations included the seal flask staying clear and the open flask being cloudy. Conclusions:microorganisms would not grow in broth when its container was heated and then sealed. He inferred that microorganisms do not rise spontaneously, they are carried in the air. -
First Microscopes (1680's)
Hooke was an early user of the light microscope, he looked a pieces of small corks and studied the nature of the cell. The newly developed instrument was used for the viewing an constant study of smaller microorganisms, and they used to think that these microorganisms came from a “vital force” in the air. -
(1668) Redi's Experiment
Redi did an experiment which connected spontaneous generation with meat exposed to air and meat not exposed to air. As he let them rot, he found that the meat not exposed to the air did not produce any maggots/flies. This bought him to the conclusion that the flies did not spontaneously generate from the meat, but were carried in the air. -
Pasteur's Experiment (mid 1800's)
He allowed air inside the flask to mix with the air outside therefore not destroying the “vital force”. He did this by using a curved-neck flask to prevent solid articles from entering the body of the flask. Broth boiled but once the neck was broken off, the broth became cloudy. He reasoned that the contamination was due to microorganisms in the air. -
Lynn Margulis (1966)
Found that bacteria and organelles show many similarities. Like prokaryotes, mitochondria and chloroplasts have circular DNA. These orgnelles also have their own ribosomes, which are the same size as those found in prokaryotes, but smaller than those found in the cytoplasm of eukaryotic cells. She came up with the endosybiosis (one organism lives inside another), which led to the formation of eukaryotic cells. -
Miller and Urey (1953)
used Oparin’s hypothesis as a starting point. *Figure 14-6- used gas that Oparin said was in the atmosphere at the time of young Earth. Gases circulated through the chamber and then sparks(lightning) gave energy to drive chemicThis experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth. This enormous finding inspired a multitude of further experiments.
