What is the central claim of Darwin's theory regarding variation and natural selection?

• A. All species were created individually
• B. Traits are not inherited
• C. Evolution occurs via sudden leaps only
• D. Variation exists within populations and natural selection favors advantageous variations

Answer: (D)

The main idea being tested is that variation exists within populations and natural selection favors advantageous variations. Darwin argued that individuals in a population vary in heritable traits, and those variations that improve survival and reproduction tend to become more common over generations. Because resources are limited and environments differ, some variants are better suited to the conditions, so they leave more offspring. Over long periods, this differential success leads to adaptation and, from common ancestry, the emergence of new species. This frames evolution as a gradual process driven by heritable variation and differential survival, not by sudden, isolated creations. The other statements conflict with this view: imagining each species was created separately contradicts descent with modification; claiming traits aren’t inherited ignores the heritable basis of variation; and asserting evolution happens only in sudden leaps misstates Darwin’s emphasis on gradual accumulation of small, advantageous differences.