Question

According to the principle of competitive exclusion
A. Two species cannot coexist in the same habitat
B. Extinction or emigration are the possible results of competitive interactions
C. Intraspecific competition results in the success of the best-adapted individuals
D. Two species cannot share the same realized niche in a habitat

Answer 1

Constant populations cannot exist which were competing for the same limiting resources. This concept is proposed by experimentally testing mathematical models. Two species in the same niche cannot coexist stably.

Complete solution: The competitive exclusion principle states that the two different species competing for the same natural resources that are limiting in the environment cannot stably coexist. The species having a slight advantage will dominate over other species and ultimately will lead to its distinction. In nature, this phenomenon is rarely observed. It is also known as Gause’s law of competitive exclusion because it was proposed by G. F. Gause. Competitive exclusion of red squirrels by the grey squirrels in Britain. The red squirrels disappeared because of the scarcity of hazelnuts whereas the grey squirrels adapted to the new environment.

Additional information:
As a consequence of competitive exclusion, the competing species often evolve some distinguishing characters in the areas where they coexist. It also helps in exploiting different ecological niches by maintaining each species. The inferior competitor shifts towards a different ecological niche during evolution.

Hence, the correct option is (D) Two species cannot share the same realized niche in a habitat.

Note: In competitive exclusion one species drives off the other one and if some members of the other species survive it’s just because they have adapted themselves to the new conditions.