Final answer:
The principle stating that two species with identical niches cannot coexist in the same habitat due to competition for resources is called the Competitive Exclusion Principle. An example is between Paramecium aurelia and Paramecium caudatum, where the former outcompetes the latter when they share the same environment.
Step-by-step explanation:
When two species have identical niches, the principle that one will be outcompeted and potentially excluded from the habitat is termed the Competitive Exclusion Principle. This principle indicates that two different species cannot sustainably occupy the same niche within the same environment because they would compete for the exact same resources. Consequently, one species will outcompete the other, which may lead to the local extinction of the less competitive species or result in the necessity for one species to evolve different adaptations.
An example of the Competitive Exclusion Principle in action involves two protozoan species, Paramecium aurelia and Paramecium caudatum. In laboratory experiments where these two species are placed together in the same habitat, Paramecium aurelia outcompetes Paramecium caudatum for food resources, eventually leading to the extinction of the latter.