Mutations and evolution
The mutations have occurred over time, by causes natural as radiation from the sun or minerals from the earth's crust. Although they are not very frequent, since they cover very large periods of time and very large populations, the probability that a mutation will appear is considerable.
Most are lethal and disappear with their carriers, but when they are beneficial they remain in the individuals of the population and are transmitted to their offspring. If natural selection acts on these genotypesand they are favorable to those environmental conditions, it can even become incorporated as a single homozygous character, making the old normal character of the population disappear. If the mutation is harmful, if they are recessive, they will remain in the population.
If the mutation is beneficial, it can improve the function of the enzyme it encodes, for example, by improving biological activity, facilitating the life of the organism that carries that mutation.
Neutral mutations neither improve nor harm the conditions of the individual who is the carrier of the mutated gene, but can be passed on to descendants. It can serve as a biological clock to know how long two species have separated since they had a common ancestor.
All cells can suffer some mutation, but the mutations that affect the gametes will affect the zygote that is formed after fertilization with another gamete and the cells that derive from it to form the new multicellular being. In addition, he will transmit the mutation to his descendants. Therefore, beneficial germline mutations will be those that cause the evolution of the species. The individual carrying the mutation has an advantage over those who do not have it, so they will be more likely to have offspring and transmit this advantageous characteristic to their descendants.
Harmful mutations only remain in the population when they are recessive. If the mutation occurs in a somatic (non-germ) cell, it will not be passed on to offspring.
When mutations appear in a certain population, the genotype changes from generation to generation, appearing individuals with characteristics different from those of their predecessors. This is how the population evolves, being able to originate new species. An example is bacteria that evolve after being subjected to antibiotics, becoming resistant.
Mutations that are detrimental to the carrier individual will be eliminated by natural selection.
In addition to natural selection, man has made artificial selection on domestic plants and animals, modifying them according to his own interest. It has achieved this by selecting the most productive individuals and crossing them with each other, obtaining different breeds, as in the dog, for example.
The evolution occurs because people change their "pool" gene, the set of genes formed by all allelesexist among individuals. If an individual has the most favorable alleles, he has an advantage over the rest, being able to survive more easily. Thus, it is more likely that it is reproduced and that these genes remain in the population.
The evolution of species occurs because the changes produced by genetic mutations accumulate. Most mutations are harmful and their carriers die, but those that produce an improvement remain in the species and are essential in the evolutionary process.
When there is a separation between some members of a population, their genetic exchange is interrupted. Being in different environments, this differentiation is becoming more and more noticeable. With the passage of time, their genetic differences will be so great that they will have become different species, being unable to reproduce among them.