Notable books in the design pattern genre include: 1  Gamma, Erich; Helm, Richard; Johnson, Ralph; Vlissides, John (1995). 2  Brinch Hansen, Per (1995). 3  Buschmann, Frank; Meunier, Regine; Rohnert, Hans; Sommerlad, Peter (1996). 4  Schmidt, Douglas C.; Stal, Michael; Rohnert, Hans; Buschmann, Frank (2000). 5  Fowler, Martin (2002).
Answer 1: The oxygen that we currently find in the air has two main sources. The first, and major, source is that oxygen is liberated as a by-product of photosynthetic chemical reactions. The second source occurs in the atmosphere itself when water molecules are split apart after being struck with ultraviolet radiation. This process is called photolysis. The molecule is broken down into one diatomic hydrogen molecule and one free oxygen. The hydrogen molecule is light, and has a quick thermal velocity,so it can escape Earth's atmosphere leaving behind the free oxygen to form a diatomic oxygen molecule. The main source of this atmospheric water was volcanic eruptions and outgassing. Basically before photosynthesis began on large scales, free oxygen molecules in the atmosphere were drawn down in oxidation reactions with free metal ions on the Earth's surface, mainly iron.
The Earth's atmosphere is mostly composed of nitrogen. Oxygen makes up just 21 percent of the air we breathe. Carbon dioxide, argon, ozone, water vapor and other gasses make up a tiny portion of it, as little as 1 percent. These gasses probably came from several processes as the Earth evolved and grew as a planet. But some scientists believe that the Earth's atmosphere would never have contained the oxygen we need without plants.