* Natural selection acts on variation within a population: Natural selection operates on the differences in traits among individuals within a population. Some individuals will have traits that make them better suited to their environment, allowing them to survive and reproduce more successfully.
* Individuals don't change: Individual organisms have a fixed set of genes. They don't evolve during their lifetime. They may change slightly due to environmental factors, but these changes are not heritable.
* Evolution happens over generations: Natural selection leads to changes in the *frequency* of different traits within a population over multiple generations. As individuals with favorable traits reproduce more, their offspring inherit those traits, causing the overall population to become more adapted to the environment.
Think of it like this: A single organism can't evolve, but a population can change over time as individuals with advantageous traits become more common.
