Question

a certain population of birds can have one of three beak lengths: short, medium, or long. birds with short and long beaks can more easily eat seeds than birds with medium beaks. a scientist studies this population of birds for ten years. most of the birds at the beginning of the study have medium - sized beaks. how might natural selection change beak length in this population of birds over time? move the labels to the boxes on the graph. graph: y - axis is frequency of beak type, x - axis is beak length (mm); labels at the bottom: long beak length, short beak length, average beak length at the end of the study, average beak length at the beginning of the study

Explanation:

1. At the beginning, most birds have medium beaks, so the "Average beak length at the beginning of the study" corresponds to the peak of the initial (dotted) curve, which is the middle box (over the dotted peak).
2. Birds with short and long beaks are more fit (can eat seeds better), so over time, natural selection will favor them. The final (solid) curve has two peaks (short and long) and a trough at medium. So the "Average beak length at the end of the study" corresponds to the trough of the solid curve (middle lower box).
3. The left box (under the left solid peak) is "Long Beak Length" and the right box (under the right solid peak) is "Short Beak Length"? Wait, no—wait, the x - axis is beak length. Wait, short, medium, long. So the left side of the graph (lower left box) should be "Short Beak Length"? Wait, no, maybe I got left and right reversed. Wait, beak length: short, medium, long. So from left to right on the x - axis: short, medium, long? Or long, medium, short? Wait, the labels at the bottom: "Long Beak Length", "Short Beak Length", "Average...end", "Average...beginning". Wait, the lower boxes: leftmost is "Long Beak Length", middle lower is "Short Beak Length"? No, that doesn't make sense. Wait, let's re - analyze:

Initial population: most medium beaks (dotted curve, peak at medium). After natural selection, birds with short and long beaks are favored (disruptive selection), so the solid curve has peaks at short and long, trough at medium.

So:

• The dotted peak (initial average) is "Average beak length at the beginning of the study" (middle upper box).
• The solid trough (medium, which is less frequent at the end) is "Average beak length at the end of the study" (middle lower box).
• The left solid peak (longer beak length) is "Long Beak Length" (left lower box).
• The right solid peak (shorter beak length) is "Short Beak Length" (right lower box). Wait, but the labels at the bottom have "Long Beak Length", "Short Beak Length", "Average...end", "Average...beginning". So matching:

Left lower box: Long Beak Length

Middle lower box: Average beak length at the end of the study

Right lower box: Short Beak Length

Middle upper box: Average beak length at the beginning of the study

Because initially, medium (middle upper) is most common. After selection, medium (middle lower) is least common, and long (left) and short (right) are most common.

Answer:

• Left lower box: Long Beak Length
• Middle upper box: Average beak length at the beginning of the study
• Middle lower box: Average beak length at the end of the study
• Right lower box: Short Beak Length