Environmental factors can influence natural selection because they can increase or decrease the amount of genetic variation in a population.
Explanation:
Natural selection is a process that involves the survival of species through changes in the expression of their genes, making possible the process of adaptation to environmental changes. It is one of the explanations for the biological evolution of species.
The second premise, necessary for natural selection to be possible, implies the existence of a variability (genetics) of traits among individuals in a population.
The other premises of natural selection are the faculty of traits to be inheritable and that genetic variability should lead to reproductive success and survival.
<em>The other options are not related to the process of natural selection, since it is not possible for natural selection to increase or decrease the number of chromosomes, in addition to the fact that genetic variability must be observed in a population, not in a single individual, to be considered natural selection </em>
