A particular population of bird exhibits variation in beak size. Several years ago, a change occurred in the environment where the bird population lives. The graph below shows how the distribution of beak size changed within the population from the point when the change occurred to the present.

Which of the following best describes the change that occurred?
A.
The change caused individuals with larger beaks to be less likely to survive and reproduce.
B.
The change caused individuals with larger beaks to be more likely to survive and reproduce.
C.
The change caused individuals within the population to grow smaller beaks.
D.
The change caused individuals within the population to grow larger beaks.

B.

The change caused individuals with larger beaks to be more likely to survive and reproduce.

Explanation:

Look at the graph: the current population shifted right from the original population. That means the new population generally has larger beaks. So A and C are wrong.

Now let's see - do they grow the larger beaks, or are they just more likely to survive and reproduce? Well remember this - they never grow them! This is called the acquired theory of evolution, and it's wrong. Lamarck was a biologist who disagreed with Darwin and thought that if giraffes just stretched their necks, the population could evolve. This isn't right; it actually happens Darwin's way, with survival of the fittest. So B is the correct answer.