Question

You observe that body mass and femur diameter are tightly and linearly correlated. What can this tell you about the propensity of natural selection to act on femur length and diameter?

A Nothing. Natural selection can produce any phenotypic outcome as long as it increases fitness.
B Femurs are important components of fitness.
Natural selection acting on body mass (or femur diameter) is constrained by physical laws dictating how biological organisms support their mass.
C Selection upon femur diameter will eventually produce an elephant with the femur diameter of a mouse.
D Nothing since most of life on this planet does not femurs.

Answer 1

Option (C), The tight correlation between body mass and femur diameter indicates that natural selection is moderated by the biomechanical needs of the organism, with directional selection favoring smaller body sizes in field mice to evade predators.

Step-by-step explanation:

The observation that body mass and femur diameter are tightly and linearly correlated suggests that natural selection is constrained by physical laws relating to how biological organisms support their mass. This correlation implies that there's a balance to maintain between femur strength and the body mass it has to support, making it unlikely for extreme deviations such as an elephant with the femur diameter of a mouse to be favorable or even viable.

In the context of field mice, predators targeting larger mice will cause a change in the population. A histogram displaying body sizes with the new population skewed towards smaller sizes would show directional selection, where the average trait shifts towards a more favorable phenotype (small body size).