Natural selection occurs when inherited differences affect survival and reproduction. Gene variants are alleles; changing their frequencies across generations is genetic evolution. Selection is one mechanism of evolution. Individuals do not turn into a needed type. Limited resources create competition, but a helpful trait never guarantees survival. Safety: No live insects, outdoor lights or predator feeding. Stop: Stop after one model generation and a reversed-background prediction. Do not capture moths or test predation.

Materials: Paper; Pencil 1. Draw ten illustrative moths: eight light and two dark. Assume colour is inherited and the model tracks only these two forms. Draw a dark resting background and write birds can more easily see contrasting moths. Food and safe resting sites are limited. 2. Use this supplied model outcome, not a catching game: the light-colour parents together leave four adult offspring; dark-colour parents together leave six. Draw the next generation as four light and six dark. Do not recolour the original moths. 3. Compare the dark share: two of ten before, six of ten after. Write four headings—variation, inheritance, competition, differential reproduction—and place one stated model fact under each. 4. Explain how colour-related differences in reproduction changed the population. Then change the background to light and predict how the advantage might change. Write one limitation: real moth inheritance, predators, movement and chance are more complex than this fixed count model. Done: Complete both generations, the two dark shares and the four-condition explanation. Proof: Keep the generation drawing and explanation. Note whether the adult supplied counts, labels or causal links; the outcome counts are provided support. Stop: Stop after one model generation and a reversed-background prediction. Do not capture moths or test predation.