The document discusses key concepts in ecology, including:
1) Ecology is the study of living organisms in their natural environment and how they interact with each other and their non-living environment.
2) Key ecological terms defined include ecosystem, community, species, population, habitat, biodiversity, autotrophs, heterotrophs, detritivores, saprotrophs, feeding relationships, niche, and the competitive exclusion principle.
3) The niche of a species describes its role, tolerance limits, and requirements within an ecosystem, and niche overlap can lead to competitive exclusion of one species.