An ecological niche explains an organism’s role in his ecosystem. Roughly speaking it can explain what is the role that the organism plays in his ecosystem, i.e. it’s job or it’s contribution to ecosystem. Or it is the mode of existence an organism has on his ecosystem. This term helps in the understanding of how organism’s interact with each other in an ecosystem. It can also be phrased as the sum of all activities and relationships a species has while obtaining and using the resources needed to survive and reproduce There were numerous definitions of ecological niche. Grinnell (1917) defined it as all the sites where organisms of a species can live (where conditions are suitable for life). This definition pertains to the “address” of the species in the ecosystem. Elton (1927) described the niche as the function performed by the species in the community of which it is a member. This definition pertains to the “address” of the species in the ecosystem. Hutchinson (1957) defined a niche as a region (n-dimensional hypervolume) in a multi-dimensional space of environmental factors that affect the welfare of a species. More info can be found from 1.http://en.wikipedia.org/wiki/Ecological_niche 2.http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/ecology/notes/niche.htm 3.http://www.purchon.com/ecology/niche.htm - With some nice examples