What is the effect of selection pressure on a population's genetic variation?

Selection pressure refers to external factors that influence which individuals within a population are more likely to survive and reproduce. When selection pressure is present, individuals with advantageous traits tend to thrive, while those with less favorable traits may not survive long enough to pass on their genes. This process can lead to a decrease in genetic variation over time.

As certain traits are favored, the alleles associated with those traits become more common, while alleles for less advantageous traits can diminish in frequency or even be lost from the population altogether. This results in a population that is more homogenous in terms of the genetic traits that confer survival and reproductive advantages, thereby reducing overall genetic diversity.

In summary, the effect of selection pressure is to selectively favor certain genetic traits, leading to a reduction in genetic variation within the population as those traits become more prevalent.