Which component best describes why selective pressures affect populations?

The correct response highlights the importance of biological variations among individuals within a population, which is central to the concept of natural selection. Selective pressures, such as environmental conditions or predation, act on these variations. For example, if certain traits confer advantages in survival or reproduction, individuals with those traits are more likely to pass them on to the next generation.

This process, driven by the existing differences among individuals, leads to the adaptation of populations over time. Without biological variation, there would be no differences for selection to act upon, and the population would lack the genetic diversity necessary to adapt to changing environments or challenges.

In contrast, changes in climate, nutritional resources, or geological events can certainly represent types of selective pressures, but they do not inherently account for why those pressures lead to changes in populations. It’s the variations among individuals that allow some to endure and thrive under selective pressures, so this option is fundamentally essential to understanding the mechanisms of evolution.