Final answer:
Dioecious species have separate male and female reproductive structures on different plants, such as in aspen, cannabis, and holly. This is in contrast to monoecious and hermaphroditic or bisexual species, which contain both male and female reproductive structures within the same individual or plant. The correct option for this species separation is 3) Dioecious.
Step-by-step explanation:
The species characterized by having either male or female reproductive structures, but not both, is dioecious. Dioecious plants have their male and female reproductive organs on separate plants, thus requiring cross-pollination between individuals to reproduce.
This mode of reproduction can be contrasted to hermaphroditic or bisexual organisms, which possess both male and female reproductive organs within the same individual or flower, and monoecious plants which also bear both male and female flowers but on the same plant.
Examples of dioecious plants include aspen, cannabis, and holly. In contrast, monoecious plants such as corn, cattail, and most species of squash bear both types of unisexual flowers on the same plant. Hermaphroditic or bisexual flowers have both male and female reproductive structures, either in the same flower or with parts maturing at different times, enabling pollination.
Therefore, the correct option for a species that has exclusively male or female reproductive structures and is not hermaphroditic or monoecious is the third option: Dioecious.