Which of the following statements reflects the mechanism of natural selection?

Step 1: Analyze the question The question asks which statement reflects the mechanism of natural selection, the process Darwin proposed to explain how species change over time.

Step 2: Explain the concept Natural selection rests on a few key ideas:

1. Variation: Individuals within a species differ in their traits (size, speed, colour, disease resistance, etc.).
2. Overproduction: More offspring are produced than can survive.
3. Struggle for existence: Individuals compete for food, space, mates and so on.
4. Survival of the fittest: Individuals with favourable traits (selective advantages) are more likely to survive and reproduce.
5. Inheritance: The favourable traits are passed on, so they become more common in later generations.

Step 3: Evaluate each option

• A. There are variations within every species. Correct. Variation is the raw material for natural selection. Without differences between individuals, nothing could be "selected".
• B. Individuals of every species are genetically identical. Wrong. If everyone were identical, there would be no advantage to select for.
• C. No organism in a species dies before sexual maturity. Wrong. Natural selection depends on many individuals dying before they reproduce.
• D. Organisms with selective advantages are less likely to survive. Wrong. It is the reverse. Those with advantages are more likely to survive and reproduce.

Step 4: Answer Option A is the only statement that is true and part of the mechanism of natural selection.

Tip: For natural selection questions, remember V-O-S-I: Variation, Overproduction, Struggle/survival of the fittest, Inheritance. Eliminate any option that contradicts one of these, such as "identical individuals" or "the advantaged die more". Option A is the V in VOSI.