Anyone else reminded of Quake2/Quake4 ... ?
This alien "lifeform" is pretty similar to the Strogg in Quake2 and Quake4 - in the way that they use remains of their defeated enemies to rebuild the next "generation" of themselves. Also Star Trek's "Borgs" come to mind.
I always liked this concept, and thought this movie was pretty good.. even though the rest of it was kind of cliché from beginning to end.