What describes the potential extent of a species based on adaptations and tolerance limits?

The fundamental niche refers to the potential range and conditions under which a species can thrive based solely on its physiological and ecological adaptations, without the influence of competing species or other biotic factors. This concept encompasses the full spectrum of environmental conditions, resource availability, and interactions that would allow a species to survive and reproduce optimally. It reflects the idealized habitat and lifestyle of the species, determined by its tolerances to factors like temperature, moisture, food resources, and habitat type.

In contrast, the realized niche is more specific and represents the actual conditions and resources used by the species in the presence of competition and other biotic interactions. Although habitat refers to the physical environment where a species lives, and population density describes how many individuals occupy a specific area, neither conveys the broader potential adaptations inherent in the fundamental niche. Thus, focusing on adaptations and tolerance clearly leads to the understanding that the fundamental niche best describes the potential extent of a species.