GX67: In snail shell polymorphism, which design best tests Explain how reproductive isolation can lead to speciation.?

The correct answer is: GX67: Use the snail shell polymorphism. Measure banded-shell counts. Change predator-abundance index; record the dependent variable from the data table; hold shell key blind check constant. Use random/systematic sampling, representative sample size and bias check. Compare observed and expected values; use critical value, significance and null hypothesis. Correlation means association; correlation does not prove causation. Keep locus-variant evidence separate from allele-frequency model evidence and selection evidence. Evaluate validity, reliability, limitation, conclusion and improvement.

For this question, start with the A-Level concept in Evolution may lead to speciation, then connect it to the scenario using speciation, reproductive isolation and a clear cause-and-effect chain. GX67: The correct option is supported by banded-shell counts, predator-abundance index, controlled shell key blind check, representative sampling, observed and expected values, and a cautious correlation judgement. Evaluate validity, reliability, limitation, conclusion and improvement. For exam-style wording, develop the link between structure, function and consequence rather than stopping after a definition.