An ecological niche is the relational position of a species or population in an ecosystem. The term fundamental niche describes the position of a species solely determined by environmental conditions. A realized niche is the position the species actually occupies, determined by competition for resources. The concept of a niche is related to renewable and nonrenewable resources because a species niche is dependent on the availability of such resources. Reducing or increasing the abundance of resources will directly effect the niche of a particular species.
http://www.sciencedaily.com/articles/e/ecological_niche.htm
http://www.physicalgeography.net/fundamentals/images/niche.gif
http://resource.rockyview.ab.ca/t4t/bio20/images/m3/004_zebra.jpg