Gaia?
The subject has been touched on before but only briefly. I guess that there is first the matter of definition. That goes a long ways towards how the subject is addressed.
If you were talking a living, breathing, conscious, entity then I would say no. There are a couple of scientists who have put forth the idea that such might be possible but they have been laughed off as crackpots. It was some years ago that I read their theory so I can not give you a set of links over it.
If you are talking a collective of life, one that in some form nutures life and keeps it going, then I am on the fence on this one. Part of me says yes, that exists, but not to our benefit. We are a result not favored or in anyway placed above any other life form. I say this because if you look, you find that "contamination" of life in all the nooks and crannies of the earth. From places we would not believe life could exist to places where we know it does as a common happenstance.
In the earth, in the hot places where no oxygen is and the heat is unbearable to us, to the depths of the sea where light does not reach, to the depths of caves and caverns where to us there should be no life, life is found. So in that sense, yes, there is a collective of life. Is that Gaia that you speak of?