Community is any group of organisms belonging to a number of different species (a population of different species) that coexist in the same habitat or area and interact through tropic and spatial relationships. Ecosystem is a community of organisms and their physical environment interacting as an ecological unit. Niche is the totality of an organism adaptation, its use of resources, and the lifestyle to which it is fitted in its community. How an organism uses materials in its environment as well as how it interacts with other organisms (i.e. it functional role) is also called its ccological niche.