The diagram documents a famous experiment by Diane Dodd. Dodd took an initial population of Drosophila fruit flies and separated them into two different containers. The first group was fed food containing mostly starch. The second group was fed food containing mostly maltose. After eight generations apart (about four months), the flies were re-introduced and could no longer interbreed. They had become two new species.
What is the most likely reason the flies evolved into two species?
Responses
A At least one of the groups of flies became sterile and unable to lay eggs.At least one of the groups of flies became sterile and unable to lay eggs.
B The two flies were really separate species to begin with, but it went unnoticed.The two flies were really separate species to begin with, but it went unnoticed.
C The two different food sources introduced many new DNA mutations very quickly and the flies changed drastically.The two different food sources introduced many new DNA mutations very quickly and the flies changed drastically.
D Separation with different food sources gave an advantage to mutant flies that could only digest starch or digest maltose. They survived and the species changed in these directions.
D Separation with different food sources gave an advantage to mutant flies that could only digest starch or digest maltose. They survived and the species changed in these directions.
D Separation with different food sources gave an advantage to mutant flies that could only digest starch or digest maltose. They survived and the species changed in these directions.
The most likely reason the flies evolved into two species in this experiment is option D: Separation with different food sources gave an advantage to mutant flies that could only digest starch or digest maltose. They survived and the species changed in these directions.
To arrive at this answer, let's analyze the choices:
Option A suggests that at least one group of flies became sterile and unable to lay eggs. However, this alone wouldn't be sufficient for the flies to evolve into two separate species.
Option B suggests that the two flies were already separate species to begin with, but it went unnoticed. However, this contradicts the information given in the question which states that the initial population was taken from the same group of Drosophila fruit flies.
Option C suggests that the two different food sources introduced many new DNA mutations very quickly and the flies changed drastically. While DNA mutations can potentially lead to evolution, the timespan of the experiment (about four months) is relatively short for such drastic changes to occur.
Option D suggests that separation with different food sources gave an advantage to mutant flies that could only digest starch or maltose. This option aligns with the information provided in the question, where the two groups were fed different food sources. The advantage provided by the specific food source leads to the survival of mutant flies specialized in digesting either starch or maltose. Over time, these specialized flies would have a selective advantage, and their populations would diverge, eventually resulting in two separate species.
Therefore, option D is the most likely reason the flies evolved into two species in this experiment.