Question

bird beak variation
bird beak size is often related to the type of food the birds eat and the size of the food source. birds with small beaks eat food items with small beaks are better able to eat larger seeds, while birds with small beaks typically eat smaller seeds.
an environmental change occurred that resulted in a reduction in one type of food, namely sunflower seeds. the change caused a shift in the distribution of beak sizes in the population. the graph shows the distribution of birds of various beak sizes before and after the observed change.
which statement is best supported by the data in the graph?
a. the percentage of birds with smaller beaks increased because they were better able to find food and survive to reach reproductive age.
b. the percentage of birds with larger beaks increased because they were better able to find food and survive to reach reproductive age.
c. the percentage of birds with smaller beaks increased because there was less competition for food with the larger - beaked birds.
d. the percentage of birds with larger beaks decreased because there was increased competition for food with the smaller - beaked birds.

Explanation:

Step1: Analyze the graph

The graph shows a shift in the distribution of bird beak - sizes after an environmental change. The original population had a normal - distribution of beak sizes (small, medium, and large). After the environmental change, the percentage of birds with smaller beaks increased.

Step2: Evaluate each option

• Option A: If the percentage of birds with smaller beaks increased because they were better able to find food and survive to reach reproductive age, this would explain the shift in the population distribution. Small - beaked birds might be more suited to the new type of food available after the environmental change.
• Option B: The graph shows an increase in the percentage of birds with smaller beaks, not larger beaks. So this option is incorrect.
• Option C: There is no information in the problem to suggest that there was less competition for food with larger - beaked birds specifically causing the increase in smaller - beaked birds. The main factor seems to be the new food source.
• Option D: There is no indication that the decrease in the percentage of larger - beaked birds is due to increased competition with smaller - beaked birds. The change is more likely related to the new food source.

Answer:

A. The percentage of birds with smaller beaks increased because they were better able to find food and survive to reach reproductive age.