Question

read this passage about two inherited traits in penstemon plants.

penstemon plants are known for their tube-shaped flowers. some penstemon plants have red flowers, while others have blue flowers.
these plants rely on animal pollinators to reproduce. if pollinators do not find and pollinate a plants flowers, the plant cannot reproduce.
some flower colors are easier for certain pollinators to see. hummingbirds can see red flowers more easily, and bees can see blue flowers more easily.

a hummingbird pollinating a penstemon plant with red flowers

the graphs below describe flower color in an isolated population of penstemon plants at the start and end of a time period long enough for natural selection to occur. at the start of this time period, the penstemon plants environment changed.

population at start
population at end

■ plants with red flowers ■ plants with blue flowers

describe how the penstemon plant population changed over this time period. use the theory of natural selection to construct a possible explanation for this change.

the percentage of plants with blue flowers in the population. this suggests that plants with red flowers were likely to reproduce than plants with blue flowers. this may have occurred because there were significantly hummingbirds after the populations environment changed. so plants with blue flowers were pollinated often than plants with red flowers.

Explanation:

1. Compare the start and end percentages: blue flowers dropped from 88% to 30%, so their percentage decreased.
2. Since red flowers became more common, they had higher reproductive success, meaning they were more likely to reproduce than blue-flowered plants.
3. Hummingbirds see red flowers better; the rise in red flowers means there were significantly more hummingbirds in the changed environment.
4. With more hummingbirds (who favor red), blue flowers were pollinated less often, leading to lower reproduction.

Answer:

The percentage of plants with blue flowers decreased in the population. This suggests that plants with red flowers were more likely to reproduce than plants with blue flowers. This may have occurred because there were significantly more hummingbirds after the population's environment changed. So plants with blue flowers were pollinated less often than plants with red flowers.