Gaia

In Greek mythology, Gaia is a goddess personifying Mother Earth. The goddess came into ecological prominence with the publication of Gaia: A new look at life on Earth by James Lovelock. His "Gaia Hypothesis" portrayed our planet as a single, unified, living, breathing organism which self-regulates so as to maintain healthy conditions for life: "...a complex entity involving the Earth's biosphere, atmosphere, oceans and soil; the totality constituting a feedback or cybernetic sysstem which seeks an optimal physical and chemical environment for life on this planet."

In effect, this self-regulating acitivity is an emergeant property of the complexly interacting physical and biological systems on the planet.

Most Earth scientists believe this description to some degree. Certainly the various planetary subsystems interact in complex ways and in so doing are altered - in biological terms, you could say they are co-evolving. And we know of many "negative feedback" mechanisms where the planet's biosphere acts to dampen out secular changes (if CO2 levels rise, plants thrive and take more CO2 out of the atmosphere). Whether these instances add up to planetary scale homeostatic behavior, much less a truly "optimising" behavior, is still open to debate.

Still, the Gaia Hypothesis is an intriguing way to consider the planet in a holistic way.