PROCESSES AND MECHANISMS OF EVOLUTION

 

MAIN PARAMETERS OF EVOLUTION

 

Darwin described evolution as “evolution by natural selection.” However, the two main parameters of evolution are variation and natural selection pressure. Since DNA was not known in Darwin’s time, he made such a definition. In fact, variation and natural selection pressure work together to enable evolution, that is, speciation.

 

How does this mechanism work?

 

As a result of a change in the habitat of a population of living organisms, for example, due to drought on one of the Galápagos Islands, the finches living there are forced to crack hard seeds. As a result, their beaks become thicker and change shape to break these hard seeds. When drought begins on the island, natural selection pressure favors the formation of thicker beaks. At the same time, within the population on the island, newborn individuals whose genetic sequences (genomes) are predisposed to having thicker beaks are advantageous and therefore selected by natural selection. Gradually, the gene frequencies of these variations within the population begin to increase. In other words, 70% of the population comes to have a genetic structure suitable for thick beaks. This continues to increase over time.

 

This process of developing thicker beaks accumulates small changes over a long period. When this accumulation of quantitative changes reaches a certain level, a qualitative transformation occurs, and the thick-beaked finches no longer interbreed with the thin-beaked finches. In other words, speciation occurs. Evolution already means the transformation of one living organism into another, the formation of a new species—that is, speciation.

 

In summary, there are two main parameters of evolution: natural selection pressure and variations with genomes predisposed to this selection pressure. Unless these two dynamics work together, speciation—that is, evolution—does not occur. As long as these two dynamics work together, speciation occurs and a new species emerges. This is what we call evolution.