A female fly, full of fertilised eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly, and their balancing organs (halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.
In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s) that led to the flightless condition could have ________.

Question

Quizplus · Accepted Answer

The loss of flight and the absence of the body segment that gave rise to flight wings suggest alterations in the development of the flies. Hox genes are known to play a major role in determining the identity and development of specific body segments in arthropods. Therefore, alterations in the expression of a Hox gene could have resulted in the missing segment and the loss of flight. Option A, duplicating all Hox genes, is unlikely to be the cause of these alterations as it would lead to a global change in body segmentation, rather than the specific loss of a single segment. Option B, paedomorphosis, involves the retention of juvenile characteristics in adult organisms, which is not consistent with the fly species described in this scenario. Option D, originating in another species, is not a plausible explanation as the scenario explicitly states that the female fly was the only one to arrive on the island.

A Female Fly, Full of Fertilised Eggs, Is Swept by High