Biosphere Contents

4. Interdependence

Organisms in ecological communities interact with each other

Types of ecological interactions and their consequences

No organism lives in total isolation from other individuals of its own species, nor from organisms belonging to other species. Rather, organisms live within the context of ecological communities, where they interact with a variety of other living things. A simple definition of an ecological community is "a group of interacting plant and animal populations that occur together in a particular area".

The consequences of ecological interactions between two individuals can be represented by a sign notation where '+' indicates that an organism benefits from the interaction, '-' indicates that it is harmed in some way and '0' indicates that it is unaffected by the interaction. Note that it is individuals, not populations, that do the interacting, even though there may well be population (or even species) level consequences.

Common types of interaction in which one individual benefits and the other is harmed include competition, predation and parasitism.

What is an ecological community?