Question

Scientists collected data about one bird population for five generations. The scientists determined the percentages of birds in the population that had specific beak shape traits, 1-6. The data are represented by the graph shown below.



The line graph titled 'Percentages of Beak Shape Traits in a Population' shows Generation from 0 to 5, in increments of 1, on the horizontal axis. The percentage of population with trait is shown on the vertical axis from 0 to 70, in increments of 10. A solid line labeled 'Beak shape Trait 1' starts at about 15%, gradually falls to 10% in generation 1, slightly rises then falls to below 10% in generation 3, then remains steady through generation 5. A solid line labeled 'Beak Shape Trait 2' starts at about 15%, gradually falls to 10% in generation 2, remains steady at 10% in generation 3, and falls to 0% in Generation 5. A solid line labeled 'Beak Shape Trait 3' starts just below 20%, falls to 10% in Generation 2, rises sharply to about 15% in Generation 3, then falls to slightly above 0% in Generation 5. The dashed line labeled 'Beak Shape Trait 4' starts at 20%, falls to below 10% in Generation 3, and continues to gradually fall to about 5% in Generation 5. Two dashed lines labeled 'Beak Shape Trait 5' and 'Beak Shape Trait 6' start slightly above 20%, rise to above 30% in Generation 1, then gradually rise to about 40% in Generation 3. At generation 3, the beak shape traits diverge. Beak shape trait 5 remains steady at about 40% in Generation 4, then falls to about 35% in Generation 5. Beak Shape Trait 6 sharply rises to 70% in Generation 5.



The birds in the studied population use their beaks to gather nectar from deep inside flowers. The scientists observed that during the five generations of the bird population, these flowers changed. The average depth of the section of the flower that holds the nectar increased during this time.



Using this information and the data from the graph, which group of birds is most likely to have the longest beaks? Identify this group and the graph that best reflects the change in average beak length over time for the total bird population.


The group of birds with Trait 6 are most likely to have the longest beaks.



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The group of birds with Trait 6 are most likely to have the longest beaks.



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The group of birds with Trait 3 are most likely to have the longest beaks.



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The group of birds with Trait 3 are most likely to have the longest beaks.



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Answer 1

Correct choice: the birds with Trait 6, and the graph that shows the population's average beak length increasing over time — especially a gradual rise followed by a sharp increase by generation 5.

Reason: flowers got deeper, so longer-beaked birds were favored. Trait 6 rises from low to ~70% by generation 5, so Trait 6 is most likely the longest‑beaked type. As Trait 6 becomes more common the population mean beak length should increase, with the biggest jump when Trait 6 becomes dominant (a gradual rise with a sharp increase at the last generation).