Question

question 1 of 20 : select the best answer for the question. image: two graphs (starting population: bell curve for neck length; after: short neck count has x, long neck peak) 1. giraffes with short necks tend to be unable to access enough food, while giraffes with long necks can reach more food at the tops of trees. this causes an advantage for giraffes with long necks. how would you explain this?
a. this is an example of bidirectional selection in which evolutionary pressures from multiple sources encourage an organism to adapt.
b. 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.
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 a stabilizing selection in which the intermediate form of a trait is advantageous compared to the extreme forms of the trait.
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Explanation:

• Analyze Option A: Bidirectional selection isn't a standard evolutionary selection type; eliminate A.
• Analyze Option B: Directional selection favors one extreme (long necks here, as short necks struggle for food). The bell curve shifts as one end (long necks) is better adapted, matching the scenario.
• Analyze Option C: Disruptive selection favors both extremes, but here only long necks are favored, and the example mentions giraffes, not cacti; eliminate C.
• Analyze Option D: Stabilizing selection favors the intermediate trait, but here long necks (an extreme) are favored; eliminate D.

Answer:

B. 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.