Evolution is the process by which different kinds of living organisms are thought to have developed and changed from earlier forms during the history of the earth. These changes take place at the genetic level when the organisms reproduce. Sometimes the evolution process is positive and sometimes it is negative.
Darwin's Theory of Natural Selection has been divided into three parts to explain clearly how evolution happens in nature. 1. variation in traits. 2. differential reproduction. 3. DNA. Resulting in one species being stronger than the other.
New traits of species can also come from transfer of genes between populations, for example through migration, or between species.
Evolution occurs when these passed on traits become more common or rare in a population, either non-randomly through natural selection or randomly through genetic drift.