Life doesn't inherently "want" to survive. It's just that if it doesn't want to survive, then, ditto, it doesn't survive.

If it didn't try to avoid death, then it would be dead. The ones that are alive are the ones that avoid death.

The ones that don't replicate, go extinct. The ones that still exist are the ones that replicate.

Biologically, yes. 

But since we're sentient beings, I'm sure we can come up with some more specific reasons.

To a biologist, this question can be answered a priori. Biological life is defined by replication. The basis of all biological life are molecular structures which are templates to guide their own synthesis. From a chemical standpoint, this property is so fundamental it is often employed as a definitional guide for biology. This is not a matter of "intrinsic drive" to replicate. It is merely that the replication process is a consequence of the molecular structure of the fundamental molecules whose physiochemical properties are responsible for the existence of biological life. For modern organisms, this means DNA, which meets the above definition (it is a template to guide its own synthesis). Thus, if we are to consider this as a purely chemical property, the existence of such structures will guarantee that replication will occur. Furthermore it will also guarantee that a form (however primitive, if we are considering the dawn of life) will occur. The first processes that gave rise to the fundamentals of biological life were primitive evolutionary processes which were purely consequences of the chemical properties of the molecules that acted as replicator units. This is expounded upon by me here:

Chemical Evolution

It's not a matter of life having an intrinsic "drive" to replicate. This discredited idea of a vital essence has long since been refuted. The modern view is that because life is based on molecules that do replicate as a consequence of their physical properties, selection processes will occur even at primitive levels (i.e during the process of chemical evolution that constituted a 900 million year period after the formation of Earth) because, since the molecules do replicate then those that will proliferate more and thus become more frequent in a pool of replicators are those who traits imbue them with improved replicative success. Again, this is purely a discussion of physical properties and not some "intrinsic drive" of any sort. As time went on and the selection process created finer machinery by which replication processes could occur, the machinery sustaining the replicators had to be able to replicate as well. Since this machinery is all under the control of and is formed from, the actual replicators (in other words, those molecules with those physical properties), they are tools evolved by which the replicators can replicate more successfully. Again, this is a relatively modern view, and is largely based off the work of Richard Dawkins in the 1970s. Dawkins' key insight was that nucleotide sequences themselves constitute the units of selection. If we begin with replicators that replicate purely on the basis of their physical properties, and replicate in such a way that allows for the process of selection to occur, then we can see that as complex machinery to sustain and aid the propogation of replication units arises, this machinery will work in such a way as to maximize the replication potential of the DNA (or whatever molecular structure is being discussed). Again, this is not a matter of the DNA having an intrinsic desire to replicate. The replicators can program the machinery (like us) in such a way that if that machinery happened to be aware and have emotional capacity, that machinery could have the desire to do something like have sex (which would lead to the continuation of genetic material) but this only occurs because selection selects for DNA sequences which tend to program their machinery to do this, because it is stochastically favorable for replicators with this property to occur. That is the crucial point. Natural selection has nothing to do with intrinsic drive to replicate. It simply has to do with the fact that any replicator which replicates more successfully will proliferate with greater frequency (which is blindingly obvious). The reason that we have the desire to replicate is because we are programmed to. And the reason that our DNA sequences program us to do this is not because of some innate desire of them to replicate, but rather because, since they do replicate, those traits which replicate more successfully will be more frequent.

The first error is in the question in the use of want to. Without getting into a debate on the latest animal research only humans can form desires. One does not anthromorphize nature. Similarly concepts such as motive and why have no place in this discussion.

Why are all blue cars blue? Why do all rectangles have four sides? Why is it that all life we see survived? The simple fact of survival indicates "behavior" which is survival prone.

Such behavior is a characteristic of social species. It is seen in ants. It is a credible question regarding humans which came first, the belief or the enemy. Anyone who has followed the lead up to wars has seen the threat come first with the reasons the other side is no damned good coming after.

The answer is very simple. Life which does not do that does not survive.

The Darwinian theory of evolution explains what is. With it the principles of survival can be deduced. Why does the only life which has survived exhibit behavior which increases the likelihood of survival? Those which do not became food long ago.

Why is there air?

If you want to understand evolution you have to take a different perspective from the one you exhibit here.

Why pain? It aids survival. It works for the simplest multicelled animals. It requires no self-image, no comprehension of being injured or damaged.

You're onto something with this.  Actually, the term "species" is kind of a pain in the ass for a lot of biologists.  Remember, linnaean taxonomy was invented before the discovery of common descent and DNA.

E.O. Wilson, the biologist who literally wrote the book on sociobiology, has spent a good bit of his writing career trying to explain in layman's terms how life "builds up" to the point of sentience and the concept of self.  It's not so hard to imagine a single cell as surviving because it did things that made it survive.  That's pretty simple.  All the things that could have become cells if only they'd have tried to survive died billions of years ago.  What we have to remember is that human consciousness is built on billions of years of 100% successful survival.  In other words, you are a direct descendent of the first replicator that was ultimately responsible for life on earth.  Every single one of your ancestors -- billions of them -- survived long enough to reproduce.  (That's a pretty amazing thought, even if it is obvious on one level!)

Flip the question around.  Considering that every one of billions of ancestors of yours did things that made it survive -- and quite automatically, without the need for consciousnees -- would it make any sense at all that suddenly, when consciousness evolved, it would have a death wish?

I don't have much to add about a self-preserving and procreating instincts of sub-human life. These properties seems to be so fundamental laws of nature, that discussing their origin is almost philosophic.
In my opinion, humans are a different cathegory. They can also function on a biologic level, but once they satisfy these basic needs, the next priority is to find the sense of life.

I have a question about a survival of species. Let's say we have a population of birds on an isolated island in Pacific ocean, rarely visited by people. The birds are thus not afraid of them. When this island becomes suddenly an object of tourists' hunting trips, the birds who survives learns to be afraid of the humans.
The question is, how does the birds learn that, and their next generations, specifically? I could understand that if one of several birds survives a direct shooting, then he has a direct learning experience. But how is this taught to the young birds? Does the old ones somehow say it to their youngs? Or does they learn it by observing the older being aware when a human walks around? Can a population which learned to fear humans forget this fear in some time?

The answer to your question lies in the fact that it is not about learning at all, but the algorithmic process of natural selection.

The fact of the matter is, within any population of birds, there will be some that have more fearful tempraments, and who will run away from any large ground predator, and there are some who will ignore large ground predators, and many other variations inbetween.

Before humans came, the birds would have had only a few predators to worry about. Those with less fearful temperaments would have dominated in the population, because the sight of a dangerous predator would be so rare. Those with fearful tempraments would be more likely to miss out on oportunities for food, nesting, etc. The thus produce fewer young and become less prevalent in the population.

If there are no natural predators for many hundreds of thousands of years, this trend can sometimes lead to flightlessness in birds.

However, as humans arrive on the island, they become an extremely dangerous ground predator to the birds. Those with fearless tempraments now are more likely to be hunted, poached, or otherwise killed by humans. They are less likely to pass on their genes to their offspring, and over time, that minority population of birds that all had fearful tempraments would come to dominate on the island.

If I recall, it's his third (fourth?). I can't remember the first language - Lithuanian? He told me a while ago.

If you would've asked about moving 6 months ago (which was before I joined the site) I was actually looking for a roommate. But then Spartan took a huge blow and I lost my job and had to move. It was in the national news actually. Some of the people here that live in the states may have read about it in the paper. I wouldn't consider my town one full of intellectuals though. It's kind of a backwater town just south of Lansing, MI. As of the 2000 census the population was 8,389, as opposed to the Lansing area at 447,728.

I knew a guy who's mother was from the Czech Republic. As I hear it, he ended up quite the drinker...

If you'd like help with sentence structure or anything I'd be glad to help. The most common issue I've noticed with your writing is improper inflection.