In sticklebacks across lakes with similar ecological pressures, parallel evolution is typically seen as:

• A. The same armor and body-shape traits are favored in each lake.
• B. Parallel evolution requires identical genetic backgrounds.
• C. There is no consistent pattern across lakes.
• D. Only random genetic drift shapes traits.

Answer: (A)

When separate populations face similar ecological challenges, natural selection tends to push them toward the same kind of solution. That repeated direction of evolution in independent groups is parallel evolution. In sticklebacks living in lakes with comparable pressures, the same kinds of armor and body-shape changes tend to be favored because those traits improve survival and performance under those conditions. So across different lakes, you see similar phenotypic outcomes even though the populations are separate. It’s about similar selection, not needing identical genetics, and it’s not a matter of random drift or no pattern at all.