The soapberry bugs shown in the figure below adapted to a change in food source in as fast as 30 years.
For evolution to occur this quickly,

Question

The soapberry bugs shown in the figure below adapted to a change in food source in as fast as 30 years. 
For evolution to occur this quickly,

Quizplus · Accepted Answer

The fact that the soapberry bugs adapted to the new food source in as fast as 30 years suggests that the mutation creating alleles for shorter beaks was already present in the population before the change in food source occurred. Without pre-existing genetic variation, evolution cannot occur. Therefore, option A is the best choice. Option B is incorrect because mutations occur randomly and are not in response to environmental changes. Option C is irrelevant to the scenario and not mentioned in the passage. Option D is also incorrect because the presence of other food sources does not guarantee that they will provide the necessary selective pressure for evolution to occur.

The Soapberry Bugs Shown in the Figure Below Adapted to a Change