 The solar system is estimated to be 6.6 billion years old.  Earth is estimated to be 4.1 billion years old.

 NH 3 Ammonia.1%  CH 3 Methane.1%  CO 2 Carbon Dioxide 92.2%  N 2 Nitrogen 5.1%  O 2 Oxygen 0%

 NH 3 Ammonia Trace  CH 3 MethaneTrace  CO 2 Carbon Dioxide.03%  N 2 Nitrogen78.1%  O 2 Oxygen20.9%

 The absence of oxygen was a key factor in the beginning of life.  Scientists may never now exactly when and how life originated on earth, but they have several hypothesis based on what they know today.

 Based on this information scientists infer that life originated in four steps.  1. Inorganic(nonliving) matter Simple organic molecules  2. Simple organic molecules Polymers(chains of organic molecules)

 3. Polymers Protocells  4. ProtocellsCells

 Inorganic(nonliving) matter Simple organic molecules.  Organic Molecules- A compound that contains carbon and is usually associated with living organisms.  The hypothesis of Chemical Evolution,1924: Alexander Oparin formed the first theory on how organic molecules might have been formed.

 He Hypothesized that energy in the UV radiation and lightning stimulated chemical reactions in the ancient atmosphere. These random chemical reactions, occurring over millions of years, produced organic molecules.

 Stanley Miller and Harold Urey performed a test on Oparins hypothesis, 1953: They made a model of the ancient atmosphere by mixing gases in a reacting chamber with electrodes simulated the lightning.  After one week, liquid was collected and analyzed, and they found amino acids and other organic molecules had formed!

 Miller and Urey showed that Chemical Evolution could have occurred under the conditions modeled by their experiment.  Other scientists have tested the Chemical Evolution hypothesis with different gases and energy sources and have produced not only amino acids but also ATP, DNA, and RNA.

 Simple organic molecules (monomers) need to organic into complex organic molecules or chains of monomers called polymers.  Example: Protein polymer is composed of a chain of amino acids. (Complex Molecule) (Simple Molecule)

 Two Events must occur for polymers to form: The monomers must be close enough to react with one another. Monomers must chemically bond.  Theories of how this occurred: Chance meetings in the early seas. They formed in evaporating puddles of water. Developed in clay formations.

 The formation of the cell membrane, needed to separate internal environment from external environment so chemical reactions of life could occur inside the cell.  Microspheres- Protein and water bubbles, look and behave like cell membranes. Could divide, but could not pass traits to offspring.

 At some point in life protocells absorbed nucleic acids (DNA, RNA). Now they could reproduce and transfer genetic information of offspring.  As organic compounds increases in the protocell, this would enable essential chemical reactions and energy production similar to metabolism. It could be truly called a living thing.  The First Cell