1.a.3 – What is the role of natural selection in the evolution of species?

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December 5, 2009 — Riccardo Sabellotti - Giacinto Sabellotti


What is the role of natural selection in the evolution of species?

To understand the concept of natural selection we should start by noting that, like human beings, specimens of an animal species have many individual characteristics and therefore are not perfectly equal to one another. The elements in common are distinctive of species, others are peculiar to the individual (for example, among equines, white coat with black stripes characterizes the species of zebras, but two zebras can be distinguished for the different height, different strength, difference in quality of teeth etc.).. Another fundamental and easily observed phenomenon is that some of the individual features can be inherited.
The variability of individual characteristics and their inheritance are objective facts always exploited by farmers to select particularly valuable breeds of livestock. Specimens with distinctive features considered positive are isolated from others and made inbreed between them; those cubs who inherit the desired qualities will remain in the group while the others  will be sent away. This way, the positive characteristics will be increasingly common in the group and, after a number of generations, the distinctive elements of a few individuals shall have become common features of the whole group, now become a variety of their particular species.
The animals in their environment form a sort of natural breeding in which each individual has numerous special features that can be transmitted to the offspring. Some quality of individual animal can, in a special environment, increase the survival of his offspring, compared to their own kind; these characters, generation after generation, will inevitably spread in the population and become common to the entire population itself, forming a new variety. This phenomenon is called natural selection.
It is important to note that, to spread the distinctive elements of an individual, it is not necessary that all the others are either eliminated or being prevented from reproducing: just their reproduction has less success, i.e., there will be a minor number of offspring able to reproduce. In nature the role of breeder is done by the environment, since they are the characteristics of the same to determine the probability of reproductive success. This is exactly the same for plants and fungi.



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