Experiments and observations indicate that natural selection acts:

• A. to create new genetic mutations in response to environmental changes
• B. equally on all traits, regardless of their effect on fitness
• C. on existing heritable variation within a population
• D. only at the level of individual organisms, not populations

Answer: (C)

Verified step by step guidance

1. Understand the concept of natural selection: Natural selection is a mechanism of evolution where individuals with traits that increase their fitness (ability to survive and reproduce) are more likely to pass those traits to the next generation.
2. Clarify the role of genetic mutations: Natural selection does not create new genetic mutations. Mutations occur randomly, and natural selection acts on the variation that already exists within a population.
3. Recognize the importance of heritable variation: Natural selection requires heritable traits—those that can be passed from parents to offspring. It acts on existing genetic variation within a population, favoring traits that improve fitness.
4. Distinguish between individual and population levels: While natural selection acts on individual organisms (those with advantageous traits survive and reproduce), its effects are observed at the population level over generations as the frequency of beneficial traits increases.
5. Reject misconceptions: Natural selection does not act equally on all traits. Traits that negatively impact fitness are less likely to be passed on, while traits that enhance fitness are favored.