Final answer:
To prove that male and female fruit flies are the same species, one must observe if they can produce fertile offspring when they mate, as per the biological species concept. Physical traits like body color and eye color can suggest they may be the same species, but mating results are definitive. Genetic analysis and cladograms can clarify their relationship if they are not the same species.
Step-by-step explanation:
To prove that a male and female fruit fly are the same species according to the biological species concept, one would need to see if they can successfully mate and produce fertile offspring. This concept defines a species as a group of living organisms that can interbreed and produce viable, fertile offspring. Since all fruit flies (Drosophila melanogaster) with a wild-type phenotype have gray bodies and red eyes, with some mutations causing changes to black bodies and/or cinnabar eyes, one can initially infer that they are the same species by their phenotype. However, to be certain, mating them would provide definitive evidence of being the same species. Genetic makeup and traits are important, but the production of fertile offspring is the key proof for the same species under this concept.
In cases where they do not produce fertile offspring, scientists can perform genetic analysis to evaluate how closely related the two flies are. Evolutionary relationships can be demonstrated using cladograms. Over time, if one type of fruit fly possesses an advantageous trait such as a more acute sense of smell, natural selection would likely favor those individuals, potentially leading to a change in the population.