[?] relationships are relationships between living things from [?] species.
In some cases these relationships are [?] to one of the species and in others they are [?] for both species.
[?] is a relationship in which one organism kills and [?] another.
[?] is a relationship in which one organism lives in or another, called the [?].
is a relationship that brings benefit to both organisms.
[?] is a close relationship between two orgams where neiher could survive in its environment without the other