I think a lot of people also confuse intelligence with consciousness. From what I've read about the neocortex and how it relates to consciousness... I'm under the impression that mammals (and birds to an extent) could be the only conscious lifeforms on the planet.
Conscious thought takes a great deal of energy, and it doesn't make evolutionary (uh oh, e-word) sense for a creature's body to be gathering all of those extra resources for a trait they do just fine without. It's a very recent evolutionary development, but we myopically have trouble envisioning a life without it.
A computer isn't conscious (yet), but it can be programmed to do some very complex and seemingly intuitive things. It's the same with biological life... the lower lifeforms could be considered biological robots. If you read into artificial intelligence, you find that there are a lot of things we consider 'intelligence', until we figure out how they work, and then it just becomes an algorithm. It's weird how studying AI taught me more about evolution and biology than most things I've read.
Watching things in my backyard actually got a little more interesting after I started asking myself those question. Somehow an ant is a lot more interesting when you picture it as a little self-sustaining procreating networked microbot.
I believe this is also what the debate on what feels pain and what doesn't is lacking. Creatures that don't make conscious choices don't need to feel pain to stay safe... their bodies simply need to automatically cause them to escape. They aren't going to resist. And even if some of them appear to experience pain biologically, how much does it matter if there's "nobody home" to feel it? I'm not advocating abuse whatsoever, but there's no point in going out of your way to protect something for its own sake when it doesn't care either way.