Ecosystem- the biotic and abiotic conditions and relationships with in a community in a given area.
Biotic- living organisms.
Abiotic- physical conditions (e.g. soil PH/temperature)
Ecology- the study of interactions which determine where organisms are, what they do and how many there are.
Habitat- the area in an ecosystem in which an organism lives.
Population- group of individuals of the same species (in the same habitat at the same time).
Community- a collection of populations (in the same habitat at the same time).
Niche- the role that an organism plays in an ecosystem, both in terms of what it brings to and takes from the community.