Which of the following best describes the effect of natural selection?

• A. It changes the genetic makeup of entire populations over generations.
• B. It causes immediate changes in individual organisms during their lifetime.
• C. It only affects non-heritable traits in individuals.
• D. It prevents any genetic variation from occurring in populations.

Answer: (A)

Verified step by step guidance

1. Understand the concept of natural selection: Natural selection is a process where individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to the next generation.
2. Clarify the scope of natural selection: It operates on heritable traits, meaning traits encoded in an organism's DNA that can be passed to offspring. Non-heritable traits, such as acquired characteristics during an organism's lifetime, are not affected by natural selection.
3. Examine the time frame of natural selection: Natural selection does not cause immediate changes in individual organisms during their lifetime. Instead, it works over many generations, gradually altering the genetic makeup of populations.
4. Evaluate genetic variation: Natural selection does not prevent genetic variation. In fact, genetic variation is essential for natural selection to occur, as it provides the raw material (different traits) for selection to act upon.
5. Conclude the effect of natural selection: The best description of natural selection is that it changes the genetic makeup of entire populations over generations by favoring advantageous heritable traits.