Speciation
Speciation is the development of one or more species from an existing species. It occurs when two populations are isolated( both geographically and reproductively) leading to almost no gene flow between the two populations.
However, inbreeding continues within the isolated populations producing more and more generations. Eventually, the members of these two groups will be incapable of reproducing with each other even if they happen to meet. In other generations, the genetic drift accumulates different changes in a subpopulation. Also, natural selection may also operate variably in these different geographic locations. For example, in the territory of one sub-population, crows may get eliminated by eagles.
But this may not be the case in the other sub-population, whereas as a result, the crow numbers will become very high. As an outcome of this, the green variation will not be selected at the first site, while it will be strongly selected at the second.
Together, the process of genetic drift and natural selection may make two isolated sub-populations more and more different from each other. This will lead to the generation of new species.
These new species may be developed:
- If DNA changes are severe enough, such as change in the number of chromosomes, eventually the germ cells of the two groups cannot fuse with each other.
- If a new variation emerges in which females are only able to mate with a few males due to their specific traits. This allows very strong natural selection for that trait.
Speciation and Evolution
Through the process of reproduction, individuals give rise to new individuals that are similar (not the same) to the parents. This similarity in progeny or offspring or child is due to the transmission of characters or traits from parents to their progeny. The transfer of characters from parents to offspring is known as heredity and the process through which characters or traits pass from one generation to another is called inheritance.
But, according to practical basis offspring are never a true copy of their parents, e.g., in a sugarcane field that are differences among individual plants, similarly in all human beings have different characteristics, complexion, height, eye colors, etc., these differences among the individuals of a species are called variations. Variations in plants are much lesser than in human beings.
The long-term accumulation of variations leads to evolving of a new species and the process is called evolution. It is a complex process and occurs over a long period of time.