In which of the following organisms does niche differentiation serve as a means of reducing intraspecific competition?

Niche differentiation (also called niche partitioning) occurs when members of the same species exploit different parts of the environment or use different resources at different times, thereby reducing direct competition among themselves. The question specifically asks about intraspecific competition, meaning competition within the same species.

The toad is the classic example used in WAEC/JAMB biology. Toads undergo metamorphosis: the larval stage (tadpole) is aquatic, breathing through gills and feeding on algae and plant matter in water, while the adult toad is terrestrial, breathing through lungs and moist skin and feeding on insects. Because the juvenile and adult stages occupy entirely different ecological niches - one aquatic and herbivorous, the other terrestrial and carnivorous - they do not compete with each other for food, space, or oxygen. This is niche differentiation within the same species.

Deer, pigeons, and tilapia do not show this pattern as distinctly. Adults and juveniles of these species occupy essentially the same habitat and feed on similar resources, so there is no dramatic niche shift between life stages that would reduce intraspecific competition.

Exam tip: Organisms with distinct larval and adult stages (such as toads, frogs, and many insects) are the standard examples of niche differentiation reducing intraspecific competition.