A niche is the role or position an organism plays in its environment. The niche or ecological role of the flower above is to receive sunlight so it can grow. Another role it plays is the food source for many pollinators that come and go. Flowers, like the one above, provides food for many herbivores. In a community, two species cannot exist together if they have the same niche but similar species can coexist if there are at least some major differences in their niches.