When different genes that make for greater or lesser chances of survival become more frequent in a population, the phenomenon is called evolution by natural selection.
First, evolution is defined as gradual changes to the traits of organisms with time.
Natural selection refers to the tendency of nature to select for or against traits that confer adaptive advantages or disadvantages in organisms respectively.
In a population of the same organisms, the gene that confers greater chances of survival is selected among numerous similar genes. This gene becomes more frequent in the gene pool of the population with time.
Thus, we say that such a population has evolved through natural selection.
More on natural selection can be found here: https://brainly.com/question/2725702
