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.
the penstemon plants environment changed to have significantly more hummingbirds. after this change, over a time period long enough for natural selection to occur, the percentage of the penstemon plant population with blue flowers decreased.
use the theory of natural selection to construct a possible explanation for how the penstemon plant population adapted to its changed environment.
having blue flowers was ____ advantageous than having red flowers after the environment changed. so the alleles for red flowers were passed on with __ frequency than the alleles for blue flowers. as a result, the proportion of the population with red flowers __. over time, the population adapted such that the percentage of plants with flowers that were easily seen by hummingbirds ____.
a hummingbird pollinating a penstemon plant with red flowers

Explanation:

1. After the environment had more hummingbirds, blue flowers were harder for the dominant pollinator to see, making them less advantageous than red flowers.
2. Red-flowered plants were pollinated more successfully, so their red flower alleles were passed on at a higher frequency than blue flower alleles.
3. More red-flowered offspring were produced over time, so the proportion of red-flowered plants in the population increased.
4. As red flowers are the ones hummingbirds see easily, the percentage of plants with visible (red) flowers for hummingbirds increased.

Answer:

Having blue flowers was less advantageous than having red flowers after the environment changed. So the alleles for red flowers were passed on with higher frequency than the alleles for blue flowers. As a result, the proportion of the population with red flowers increased. Over time, the population adapted such that the percentage of plants with flowers that were easily seen by hummingbirds increased.