Population: It is a grouping of individuals of the same species inhabiting a given area.
Biological Community: It is an assemblage of the population of different species present in an area which show interdependence and interaction like competition, predation, host-parasite, amensalism etc.
Ecosystem: It is composed of a biological community, integrated with its physical environment through the exchange of energy and recycling of the nutrients.
The ecological niche of organisms represents, the range of conditions that it can tolerate, the resource it utilizes and its functional role in the ecological system. Each species has a distinct niche and no two species are believed to occupy reproduction in its habitat through natural selection.