Short Notes:

Whether it is the atmosphere, land, or water, nitrogen is often involved in chemical reactions. Factories and volcanoes spew out nitrogen, which is fixed, or converted into usable form, by interaction with sunlight and lightning. Rain brings nitrogen back to Earth. Nitrogen, essential to life, is used to form amino acids to build protein. Plants and animals ingest and excrete nitrogen. Other nitrogen compounds wash into rivers and oceans, where they go through further chemical changes. Together, these events make up the nitrogen cycle.