Answer:
The medium ground finches with smaller beaks will gradually fade of the entire population.
Step-by-step explanation:
If a population of medium finches in which some members survive better as a result of being able to crack Tribulus cistoides fruits with their large, deep beaks colonizes a nearby island in which the fruit is the primary food round the year, one would certainly expect member without large, deep beaks to gradually fade off the population.
Natural selection will automatically select for members of the population that are better adapted to the environment while those that are less adapted are considered weak and gradually die off the population.
FInches that are better adapted to the environment seek out each other for reproduction and are able to contribute more to succesive generation unlike those that are poorly adapted. This is otherwise known as the survival of the fitest.