evolution
Evolution occurs as organisms acquire and pass on new traits from one generation to the next generation. Its occurrence over large stretches of time explains the origin of new species and the great diversity of the biological world. Extant species are related to each other through common descent, and products of evolution over billions of years. Analysis of the DNA of different organisms indicates there is a similarity among very different organisms in the genetic code that help make proteins and other molecules. This genetic code is used by all known forms of life on Earth. The theory of evolution suggests that the genetic code was established very early in the history of life, and some studies suggest it was established soon after the formation of Earth. The timeline of the evolution of life, shown in Figure below , outlines the major events in the development of life.