Starting Population Count
Spine Density
Spine Density
3. Cacti with very few spines tend to be eaten by animals, and cacti
with many spines tend to be preferred by parasitic insects. This
causes cacti with an average number of spines to be preferred. How
would you explain this?
A. This is an example of a stabilizing selection in which the
intermediate form of a trait is advantageous compared to the
extreme forms of the trait.
B. This is an example of bidirectional selection in which
evolutionary pressures from multiple sources encourage an
► organism to adapt.
C. This is an example of a disruptive selection in which the
population of cacti is divided and well defined.
D. This is an example of directional selection in which one end of
the bell curve is better adapted to its environment than the other
end.