Question

question 37
1 point
a thin - shelled crab can more readily move to escape a predator than can a thick - shelled crab, but it is more vulnerable to predators that drill through the shell. because of these opposing forces, shell thickness for many types of crabs has remained within a narrow range over a long time. this would be an example of __.
a dispersive
b delayed
c directional
d stabilizing
e disruptive

Explanation:

To solve this, we analyze the types of natural selection:

• Stabilizing selection occurs when intermediate phenotypes (here, moderate shell thickness) are favored, reducing variation and keeping traits within a narrow range. The crab's shell thickness is maintained due to opposing selection pressures (thin shells help escape, thick shells resist drilling), favoring an intermediate thickness.
• Dispersive (disruptive) selection favors extreme phenotypes, directional selection shifts towards one extreme, and "delayed" is not a standard selection type. Thus, this is stabilizing selection.

Answer:

D. stabilizing