Ecosystems, organized entities resulting from the action of ecological factors: the structure of ecosystems

More about ecological niche :

In this picture you have an example of niche differention with bacteria.

Source of the image : bioninja.com

<!> Some species may not be able to occupy their entire niche due to the presence or absence of other species.

Ecologist Joseph Connell studied two species of barnacles - Balanus balanoides and Chthamalus stellatus - that have a stratified distribution on rocks on the Scottish coast. 

In nature, Blanus species does not survive on the top of rocks because Balanus does not resist to desiccation (drying) incurred at low tide. Its niche is similar to its fundamental niche. However, Chthamalus species is usually concentrated on the upper rock strata. To determine the fundamental niche of the species, Connell he took back Balanus species from lower rock strata.

When Connel took back Balanus population from lower rock strata, Chthamalus population spread in this area.

The fact that Chthalamus had invaded this area, free from Blanus population indicates that the real niche of Chthamalus species is smaller compare its fundamental niche because of competitive exclusion.