Following an approach of explaining biological processes on earth the Gaia theory says (the surface) of planet earth including its biosphere can be viewed as a single living organism that every life form is a part of. Sounds familiar? Yes, I bet you’ve watched Avatar in cinema.
The Gaia theory has been developed by biologists Lynn Margulis and James Lovelock in the 1960s. According to them the biosphere as the whole of all organisms creates and maintains conditions required for life and evolution.
Lovelock, however, defines life as a self-preserving, self-similar system of feedback loops like Humberto Maturana’s autopoiesis; as a self-similar system, life could be a cell as well as an organ embedded into a larger organism as well as an individual in a larger inter-dependent social context.
» Wikipedia.org: Gaia Hypothesis…
» Ecolog.org: Lovelock…
The Open University has compiled a documentary about that theory featuring Lovelock himself: