Jfkaua, I think you'll never get a definite answer to that question, when ethics are concerned. Why? Because there is no definite answer. As for me, I think what defines life is that a living being has a will to survive. We can do anything we want to the most "intelligent" robot, and if it doesn't have any kind of "I will survive!" programme, it will simply not defend itself. That brings us to "And if it does have that kind of software?" Well, then it's still not living because it needed to get that software written on its harddrive. However, that's my point of view.
You could also say that if "something" is able to feel emotions, it lives; I'm sure that you can find some kind of emotion in any plant. Again, there is no definite answer.
Don't cry because it's over, smile because it happened.