Again, it seems to me you're putting some special significance on life, possibly from a religious outlook. The fact is, all of these questions fall away if you just accept that life is no more than one more scientific, physical process. It's a ton more complicated than a rainbow, but it all obeys the laws of physics at the core of it (with a little Quantum Mechanics, even, to spice things up).
Many "organisms" have been created throughout the history of the universe. Most just died off. A few had the peculiar property that they could reproduce, so more of them keep coming up.
At least, that's my preferred theory.
It essentially boils down to which of two explanations you choose to believe:
1) Some god designed us, and loaded us with this wish so we'd stick around.
2) It's all random, all natural. We have this instinct simply because having it in the past is what allows us to be here now. There is no other reason behind it.
Again, choose what you'd wish (including some alternative I didn't list here). I can give you evidence and explanations, even recommendations, but I won't tell you what to believe.
