Make a hypothesis about how you think the two species of Paramecium sp. will grow alone and how they will grow when they are grown together.

In a community, every species interact with each other. This results in the competition among them for food and habitat. The competition is more when the resources are limited and every species compete for it. Thus the efficient species will survive and the weaker one will perish. This is known as the competitive exclusion principle.

According to this principle, two species cannot live together in the same habitat and have the same niche. Niche is the resource used by individual species and it should not be shared by many species.  

If the species want to coexist in a community without any competition the niche should be different. Otherwise, it leads to evolution.

Because if resources would overlap in use, the species which less dependent on the resource will be selected for evolution. If both the species is unable to evolve and rely on the same niche, then there is rigorous competition. The species which is powerful and fit exploit the resource and this leads the other species to extinction.

This competitive exclusion principle has shown in the two paramecium species - Paramacium aurelia and Paramecium caudatum. When they are grown individually in the culture medium they thrive. But when they are grown together in the same culture medium, Paramecium aurelia extinct the Paramecium caudatum for food.