In the virtual lab, why did you compare pelvic structures of stickleback populations from two different lakes?

• A. To test genetic uniformity across all lakes
• B. To compare the trait in populations living in two different environments
• C. To measure growth rate
• D. To study feeding habits

Answer: (B)

The main idea is that a physical trait can differ between populations because each environment imposes its own selective pressures. Pelvic structures in sticklebacks are a well-known example of how morphology can adapt to local conditions, such as predation risk or available resources in a lake. By comparing populations from two different lakes, you’re testing how the environment in each lake shapes the trait. If you see different pelvic forms between the two populations, that suggests environmental differences are driving that variation, pointing to local adaptation. It’s not primarily about growth rate or feeding habits, and it doesn’t require genetic testing to draw the same conclusion about how environment influences the trait.