Final answer:
The competitive exclusion principle states that two species competing for the exact same resources cannot coexist in the same niche. This leads to either extinction or the evolution of specializations to reduce competition. An example is provided by Paramecium experiments, where one species outcompeted the other, resulting in its extinction.
Step-by-step explanation:
Competitive Exclusion Principle
The competitive exclusion principle is a concept in ecology that explains the outcome of competition between different species. It states that two species cannot coexist if they occupy the exact same niche, as they will compete for all the same resources. This principle has profound implications on the dynamics of ecosystems. In situations where resources are limited and species compete for these, one of two things can happen: one species may drive the other to extinction, or specializations may evolve in both species, leading to different niches and reducing direct competition. For instance, the classic experiment with Paramecium aurelia and Paramecium caudatum demonstrates competitive exclusion; when both species were grown together, P. aurelia outcompeted P. caudatum, causing the latter to go extinct.
This principle does not promote coexistence between competing species directly; instead, it often leads to increased pressure to specialize and find unique ways to survive within an ecosystem, thereby decreasing direct competition for resources. This process can lead to decreased biodiversity if one species completely outcompetes another, or it can encourage biodiversity if species adapt by evolving different ecological niches.