Final answer:
The principle of competitive exclusion, stating that two species cannot occupy the same ecological niche, was first formulated by G. F. Gause. It emphasizes that coexisting species must have different niches to avoid direct competition for the same resources.
Step-by-step explanation:
The principle of competitive exclusion was first formulated by 1) G. F. Gause. This principle states that two species competing for the same resources cannot coexist at constant population values if other ecological factors remain constant. Essentially, if two species are competing for exactly the same resources, eventually the one that uses the resources more efficiently will outcompete and eliminate the other.
According to the competitive exclusion principle, for two species to coexist in the same habitat, they must have different niches or ways of life. This often leads to an evolutionary divergence known as character displacement, which allows them to utilize different resources and thus live together without direct competition for the same resources.