How does Darwin's theory explain inherited traits?

Darwin's theory of evolution by natural selection emphasizes the role of variation within populations and the heritability of these variations. The correct answer highlights that a significant portion of the traits observed in individuals is heritable, meaning they can be passed from parents to offspring through genetic inheritance. This heritable variation is crucial for natural selection to operate because it allows for the differential survival and reproduction of individuals based on their inherited traits.

When certain inherited traits provide a survival or reproductive advantage in a given environment, these traits are more likely to be passed on to subsequent generations. This cycle leads to the gradual evolution of species, as advantageous traits become more common within the population over time. In summary, the understanding that much of the variation seen in traits is heritable is central to Darwin's explanations of how evolution occurs.