Though we may think of the scientific definition of life as objective, it is as human a construct as any other. In this case, it can even be an obstacle to noticing – and internalizing – that Judaism has a very different take. From the beginning, the Torah refers to animals as living; plants, however, are never described as such. The main difference between animals and plants is free movement. (Interestingly, though plants are not described that way, moving water sometimes is. Of course, it is a figurative non-literal use of the term since water does not move itself.)
The reason movement is so important is that it is the basis of action; and it is ultimately this G-d-like ability to act that is equated with life. True, we generally don’t hold animals accountable; yet their ability to act is what prompts the Torah to occasionally speak about evil animals (as in Bereshit 37:19). That must be why the Torah concerns itself so much with animals. And that is also why, no matter how valuable a stone or plant might be, the main sacrifices have always been animals. By ascribing life to them and thereby placing them in a separate category that also includes people and G-d Himself, the Torah is telling us that even the smallest, simplest animal is fundamentally more important than anything the Torah does not describe as living.
Among other important lessons from this is that the only way to measure the importance of something is by its resemblance to G-d. And in the case of man, that is often up to us.
