How does natural selection affect a population?

Natural selection is a fundamental mechanism of evolution that operates on the premise that certain traits can confer advantages that enhance an organism's chances of survival and reproduction in a given environment. When individuals with advantageous traits are more likely to survive and reproduce than those without these traits, these beneficial characteristics become more common in the population over time.

This process of favoring organisms with advantageous traits leads to adaptations that help populations become better suited to their habitats. For example, if a particular trait helps an organism evade predators or access food more effectively, those individuals are more likely to survive long enough to reproduce, passing those advantageous traits to the next generation. Over numerous generations, this selective pressure can significantly shape the traits of the entire population, leading to evolutionary change.

In contrast, the other options highlight misconceptions about natural selection. For instance, genetic diversity may decrease over time due to a preference for specific traits, but that is not the primary effect of natural selection itself. Furthermore, organisms without advantageous traits generally do not thrive under natural selection; rather, they are less likely to survive and reproduce. Lastly, natural selection does not lead to equal survival rates since it inherently favors certain traits and, consequently, certain individuals within a population.