A population of mice has been monitored for change over several generations.Following are five different bones and the changes to their means and extents of variation.
Tibia: Mean increased 0.14 units; variation decreased.
Femur: Mean increased 0.08 units; variation increased.
Ulna: Mean did not change; variation increased.
Clavicle: Mean did not change; variation decreased.
Radius: Mean decreased 0.12 units; variation decreased.
Which is most likely to be under stabilizing selection?
A) Tibia
B) Femur
C) Ulna
D) Clavicle
E) Radius

Question

A population of mice has been monitored for change over several generations.Following are five different bones and the changes to their means and extents of variation. 
Tibia: Mean increased 0.14 units; variation decreased.
Femur: Mean increased 0.08 units; variation increased.
Ulna: Mean did not change; variation increased.
Clavicle: Mean did not change; variation decreased.
Radius: Mean decreased 0.12 units; variation decreased.
Which is most likely to be under stabilizing selection?
A) Tibia
B) Femur
C) Ulna
D) Clavicle
E) Radius

Quizplus · Accepted Answer

Stabilizing selection favors traits that are already well adapted to the environment and therefore selects against extremes. The fact that the mean and variation of the clavicle did not change suggests that it is already well adapted and not undergoing significant directional or disruptive selection. Additionally, the decrease in variation could indicate the removal of deleterious mutations that would have disrupted the fitness of the trait.

A Population of Mice Has Been Monitored for Change Over