Review and connect the unit's big ideas -- alleles, Punnett squares, mutation, selective breeding, natural selection, fossils, and adaptation -- through one integrated finch case study.
This unit traced one continuous story: traits are controlled by genes and alleles, predictable with Punnett squares (weeks 19-20); brand-new variation ultimately comes from mutation (week 21); humans can deliberately reshape a population's traits through selective breeding (week 22), while nature reshapes populations through natural selection, using the exact same raw material of existing variation (week 23); and the fossil record, studies of adaptation, and multiple independent lines of evidence all document that this kind of change has really happened, repeatedly, across the history of life (weeks 24-26).
A famous real study ties every piece together: researchers Peter and Rosemary Grant spent decades directly measuring beak sizes in a Galapagos finch population. During a severe drought, small, soft seeds became scarce, leaving mostly large, hard seeds. Finches with larger, stronger beaks survived and reproduced better than finches with smaller beaks, and the very next generation measured had a noticeably larger average beak size -- natural selection, caused by a real environmental change, directly measured within a single population in real time.
Mastery looks like: They can correctly answer at least one question from each major idea in the unit and explain the Grant finch study as a real, directly observed case of natural selection.
Common stumbles: Mixing up selective breeding with natural selection; describing natural selection as something that happens to one organism rather than a change in a population's trait frequencies over generations.