Ecology And Ecosystems QBA Exam 1 Practice Test

The main idea is that a species has a potential range of environmental conditions in which it could survive and reproduce, but in the real world its actual distribution is narrowed by interactions with other organisms. The fundamental niche is this broader, abiotic tolerance—the full set of conditions under which the species could persist. The realized niche is the subset of those conditions that the species actually uses in nature, shaped by biotic interactions like competition, predation, and mutualism. A classic example uses barnacles on a rocky shore. One species can tolerate a wide range of salinities and moisture levels, so its fundamental niche would span much of the intertidal zone. In practice, however, competition for space with another barnacle restricts where it can persist, so it is found only higher up where the competitor cannot dominate. That narrower distribution represents its realized niche. Other statements that mix up the ideas—such as saying the fundamental niche is the actual distribution or that a realized niche is simply about energy flow—don’t fit how niches are defined, because they confuse potential tolerances with actual occupancy or swap abiotic limits with energy dynamics.