Definition of Realized Niche
Realized niche is referred to as the position of the environment that is being occupied by a species in an ecosystem. Unlike a fundamental niche that represents the conditions of an environment as a whole, the realized niche only tells us about where the species are living. This is also known as post competitive niche.
An organism in a fundamental niche takes advantage of all biotic as well as abiotic factors and they do not face any kind of pressure and competition from other surrounding species. But as soon as other organisms arrive, there begins the competition for food and space. the organisms, therefore, have to adapt to the new conditions of their realized niche. The realized niches are smaller in size than fundamental niches.