Question

In an aquarium two herbivorous fishes are living together and feeding on phytoplanktons. As per the Gause principle one of the species is to be eliminated in due course of time but both are surviving well. Give possible reasons.

Answer 1

Hint:-Georgy Gause proposed the theory of competitive exclusion based on a series of experiments that he performed on 2 species of Paramecium, P. aurelia, and P. caudatum. According to this theory, two species sharing a common niche cannot co-exist provided all other external factors remain unchanged. In short, only one of the two species can survive.

Complete Answer:-In this case, two herbivorous fishes are living in the same niche and feeding on phytoplankton. In the aquarium, unlimited food resources are available in the form of phytoplankton. Moreover, the population inside the aquarium is very less as there are just 2 fishes inside. In short, there is sufficient food and less number of individuals, which means that the competition is also less.

Apart from this, as both the fishes are herbivorous there is no danger of predators in that niche. This can ensure better survival of both the fishes. And as neither of the species has been eliminated, niche overlapping may affect the expansion and development of individuals. However, studies have shown there is a fair chance that two species in the same niche can co-exist depending upon the fact as to how they segregated their use of the available resources.

Note:- Each species has a particular position as well as function in the community or environment in which it lives. According to the Gauss's principle, no two species can survive in the same niche. However, the competitive exclusion principle is rarely observed in natural ecosystems, and many biological communities appear to violate this law.