Question

two species of flies, drosophila melanogaster and drosophila simulans, can mate. they usually do not mate, however, even if they are kept together in a laboratory. males court the females of both species, but the females prefer to mate with males of their own species. which isolating mechanism does this describe?
artificial
behavioral
anatomical
temporal

Explanation:

1. Analyze "artificial": Artificial isolation is human - made, like separating species in a zoo. The fly mating preference is natural, so not artificial.
2. Analyze "behavioral": Behavioral isolation is about species - specific behaviors (like mating rituals, preferences) preventing inter - species mating. Female flies prefer their own species' males, which is a behavioral choice.
3. Analyze "anatomical": Anatomical isolation is due to physical (body structure) differences preventing mating. Here, no such physical barrier is mentioned.
4. Analyze "temporal": Temporal isolation is about different species mating at different times (seasons, times of day). The problem doesn't mention time differences.

Answer:

behavioral