All the plants, animals and people in an area and their relationships.
The quality of being acid.
Combination of substances.
The action of contaminating.
The top covering of the Earth where plants grow.
A structure with a roof and walls.
Unhealthy condition caused by an infection or disorder.
Likely to cause harm.
Animals and plants living in a natural conditions.
A covering on a surface.
Adjective related to the natural conditions.
