In contrast, certain animals have such outward differences that people choose to believe they are different species altogether. For instance, most people will quickly think that Great Dane and Beagle are different species.
Therefore, scientists commonly group organisms to a given species if they can interbreed.
Szlacheta common hybridization is the process whereby organisms of two different species produce a new species through breeding of such different species.
For instance a mule is a product of breeding between a female horse and a male donkey. Now, this mule has no mixing of genes of the horse as well as that of the donkey; that’s why it cannot reproduce and is often referred to as sterile. This can explain why the donkey and the horse belongs to different species.
Today, such a condition known as biogeographic isolation leads to creation of new species that may have evolved from a single parent species of an organism.
Said to be allopatric speciation, the parent species of an organism becomes divided into two or more populations geographically. Sometimes the landscape is changed by shifting the course of a river or there occurs an earthquake that actually divides the population.
These groups, when separated, experience genetic differences. Their genetics remains dynamic and, with time, manifests more through the phenotype of the young. The kind of genetic changes mentioned above take place due to the organisms having been experiencing changes in their environment as a way of surviving.
That is, as each of the different populations continues to exist in their own unique groups they can evolve prezygotic or postzygotic isolations mechanisms that would render them unfit for mating. For instance one population could be new to newer sex habits, which are almost unlike those of the other population. They will not be compatible for breeding even though if the geographical isolation he or she is facing were to be lifted.
Indeed, it can appear that sometimes there is no need for geographical and building-up factors to have a separate species. At first, there is a paradox which concerns me: why do organisms of the same species living in the same territory do not attempt to reproduce? But let us examine the case of the North American apple maggot fly.
As the name would imply, the North American apple maggot flies parasitize with apples trees. However, formerly, it was the hawthorn tree that was their host as we shall see later in this paper.
As European settlers began cultivating apples in this region they formed part of the diet of some of these flies. The flies that hatched out from them also lay eggs only on the apple trees and never strayed into the hawthorn area. Thus, we see that two kinds of species of flies evolved – one that was associated with their prior diet of hawthorn tree and the other that endorsed the new diet the apple tree.
No barrier prevents the two species from hybridization. The apple flies can decide where to get their food from by themselves and the same goes for the hawthorn. But they don’t, this results in isolation even in absence of geographical barriers that usually hinder interaction.
