What defines the fundamental niche of a species?

The fundamental niche of a species refers to the complete range of environmental conditions and resources that a species can potentially utilize in the absence of any limiting factors such as competition or predation. In other words, it defines the full theoretical spectrum of ecological roles and conditions under which a species can survive, grow, and reproduce.

When considering the options, the one that aligns with this definition is the one that describes the full potential range of factors a species can use. This broad inclusion encompasses not only the physical space but also the resources and environmental conditions necessary for the species’s survival.

The other options either focus on specific aspects of ecosystems or are too narrow in scope. One option relates to the carrying capacity of an ecosystem, while another discusses the actual niche a species occupies, which is more about the realized niche rather than the fundamental niche. The final option addresses interactions within an ecosystem, which are important but don't define the fundamental niche itself. Thus, the correct answer captures the essence of what defines a species’ fundamental niche comprehensively.