The term used for the development of new species from a common ancestor is called speciation. This evolutionary process occurs when populations of a species become reproductively isolated, leading to genetic divergence due to natural selection, mutation, and genetic drift. Over time, these genetic changes accumulate to the point where the populations can no longer interbreed, resulting in the emergence of distinct species. Speciation can occur through various mechanisms, including allopatric speciation (due to geographic isolation) and sympatric speciation (through behavioral or temporal isolation), contributing to the rich diversity of life observed on Earth.