What is the primary evolutionary consequence of natural selection acting on heritable variation?

• A. No changes in allele frequencies
• B. Changes in allele frequencies over generations (adaptation)
• C. Random genetic drift exclusively
• D. Immediate appearance of new mutations

Answer: (B)

Natural selection acting on heritable variation changes allele frequencies across generations. When certain genotypes have higher reproductive success, their alleles appear in more offspring, increasing those alleles in the population while less advantageous alleles decline. Over time, this shift in allele frequencies leads to adaptations that better fit the environment. This is different from random genetic drift, which changes frequencies by chance rather than fitness differences, and it’s not about new mutations appearing immediately—mutations arise randomly, and selection acts on the variation that already exists.