Which is a key requirement for natural selection to operate?

• A. The environment is static
• B. All traits are non-heritable
• C. Variation in heritable traits
• D. Random mutation

Answer: (C)

Variation in heritable traits is what makes natural selection work. For selection to change a population over generations, individuals must differ in traits that can be passed from parents to offspring. Those differences in inherited traits allow the environment to “select” certain variants, so they become more common as generations pass. If the traits aren’t heritable, advantageous differences won’t be passed on, and the population won’t evolve in response to the environment. An environment doesn’t have to be changing for selection to occur, and while mutation is a source of new variation, the key requirement is that the variation is heritable so it can be acted on across generations.