DAT Ecology Practice Exam

The main idea is understanding how wide a species could potentially survive given its physiology and resource needs, without other factors getting in the way. The fundamental niche is the full set of environmental conditions under which a species can survive, grow, and reproduce, including the range of tolerable temperatures, moisture, salinity, pH, and the resources it can use, assuming no biotic interactions limit it. In other words, it’s the theoretical space defined by the species’ biology. Biotic interactions like competition, predation, and parasitism can shrink that potential space in the real world, producing the realized niche, which is smaller and actualized within a community. That’s why wording about the portion actually occupied due to interactions describes the realized niche, not the fundamental one. Similarly, geographic range and the actual area used in a community can be influenced by dispersal and historical factors, not just environmental tolerance. So the correct concept is the full range of environmental conditions under which a species could survive and reproduce.