During the process of cell division, spontaneous changes within the genome can arise, called mutations. These are errors occur when copies of the DNA within the cell are made; mutations may range from small changes called single nucleotide polymorphisms, to large scale deletions, and additions which span multiple genes.
These mutations form variants which become stable within a population, leading to the formation of separate, genetically distinct populations called species. New species arise through several evolutionary mechanisms such as:
allopatric speciation- physical barriers to gene flow ; isolation of groups which evolve separately in their environments by accruing suitable traits, to become a new species
peripatric speciation- similar to allopatric speciation, but one group is much smaller, making the unique traits more notable, or distinct
parapatric speciation- subpopulations in a large geographic region evolve reproductive isolation by mating with those nearby, however they continue to undergo gene exchange along a common border region
and sympatric speciation- absence of physical barriers which hinder gene flow; reproductive isolation arise through many forms of the same genes called polymorphisms
