Describe the process of speciation.

A population is split into two groups by some form of barrier, either physical, such as a mountain range, or behavioral, like looking for food at different times of day. This means that the two populations cannot interbreed. There is variation in each of the populations, and each of the different environments causes them to have different selective pressures acting upon them that causes the selection of different attributes. Over time this causes the 2 populations to become so different that when reintroduced to each other, they can no longer interbreed to proudce fertile offspring, showing that they are now different species