This principle, first proposed by Charles Darwin and Alfred Russel Wallace, states that:

* Variation exists: Individuals within a species have different traits.

* Heritability: These traits can be passed down from parents to offspring.

* Survival and Reproduction: Individuals with traits better suited to their environment are more likely to survive and reproduce.

* Change over time: Over many generations, the advantageous traits become more common in the population, leading to gradual changes in the species.

This process of gradual change over time driven by natural selection is what leads to the diversity of life we see today.