Question

Starlings produce an average of five eggs in each clutch. if there are more than five, the parents cannot adequately feed the young. if there are fewer than five, predators may destroy the entire clutch. this is an example of disruptive selection.
b. stabilizing selection.
c. directional selection.
d. none of the above. the occurrence of large or small beak sizes among seed crackers in the absence of medium sized beaks is an example of directional selection.
b. stabilizing selection.
c. disruptive selection.
d. none of the above. a scientist measures the circumference of acorns in a population of oak trees and discovers that the most common circumference is 2 cm. what would you expect the most common circumference(s) to be after 10 generations of stabilizing selection? 2 cm

Answer 1

Question number one:
The correct answer is B
In the case of the starlings and their offspring, we can observe the workings of a stabilizing selection. (Presented in image number one).
Stabilizing selection tends to eliminate the extremes and favor the medium value of a trait, in this case, the number of offspring.

Question number two:
The correct answer is C.
In this example, we can observe the disruptive selection.
This type of selection favors the extremes and eliminates the medium values. In our examples with seed crackers, this means that the birds with large or small beaks are favored and the ones with medium sized beaks are eliminated. ( see image number two)

Question number three:
The correct answer is 2cm.

As we have seen on the graph number one, stabilizing selection tends to favor the medium values of a trait.
In the case of the acorns, the stabilizing selection will favor the 2cm circumference acorn, and after 10 generations we could expect the most common cicrumference to stay 2cm, because it was favored by the natural selection.