Question

read this passage about a variable inherited trait in alewives.
alewives are small fish found in oceans and lakes. alewives eat prey such as zooplankton, which come in different sizes.
alewives with a bigger gape width, which is the distance between the corners of the fishs mouth, are better at catching bigger zooplankton. alewives with a smaller gape width are better at catching smaller zooplankton.
an alewife with its gape width shown
the average size of zooplankton in the alewives’ environment decreased. after this change, over a time period long enough for natural selection to occur, the average gape width decreased in the alewife population.
use the theory of natural selection to construct a possible explanation for how the alewife population adapted to its changed environment.
having a larger gape width was advantageous than having a smaller gape width after the environment changed. so the alleles contributing to smaller gape widths were passed on with frequency than the alleles contributing to larger gape widths. as a result, alewives with smaller gape widths became common. over time, the population adapted such that the average gape width moved a size best suited for eating large zooplankton.

Explanation:

1. After the zooplankton size decreased, alewives with smaller gape widths were better at catching prey (since smaller gape is good for smaller zooplankton). So a larger gape was "less" advantageous.
2. Alleles for smaller gape would be passed on more (higher frequency) because those alewives survived/reproduced better.
3. With more alleles for smaller gape, alewives with smaller gape became "more" common.
4. The average gape width would move "away from" a size for large zooplankton (since the environment now has small zooplankton, so selection favors smaller gape).

For the first dropdown: Since smaller zooplankton are now more common, a larger gape (good for large zooplankton) is less advantageous. So "less".

For the second dropdown: Alleles for smaller gape (which is now advantageous) are passed on with "higher" frequency (because those alewives are more successful at surviving/reproducing).

For the third dropdown: As more alleles for smaller gape are passed on, alewives with smaller gape become "more" common.

For the fourth dropdown: The average gape width moves "away from" a size suited for large zooplankton (since the environment changed to favor small zooplankton, so selection pushes the average gape to be smaller, away from the large - suited size).

Answer:

1. less
2. higher
3. more
4. away from