Nitrogen is important for all varieties of life on Earth. It is an element in all amino acids, as incorporated directly into proteins, and is present in the bases that define nucleic acids for instance RNA and DNA. The nitrogen cycle is the process by which nitrogen is changed between its a variety of chemical forms. This transformation can be executed through both biological and physical procedures. Important processes in the nitrogen cycle include: fixation, ammonification, nitrification and denitrification.