Biology as we know it would only occur on a planet such as Earth. But earth-like planets are probably so distant from each other that we will never encounter, or even observe possible effects of, life that lives on them. And what would be the point if most of it was just microbial life? Certainly would be a fantastic discovery, but wouldn't change anything for people on earth.

I think the real question on people's minds is: what are the requirements for consciousness? Most people would think that a highly developed brain is needed, and that follows from the same biology that all life on earth possesses. So most would think that consciousness could not occur where there is no earth-like biology.

I am hoping to avoid a religious discussion, but could consciousness arise in other ways? Beings of energy, or semi-static electromagnetic fields? Sentient beings that exist in the gaseous state? What about collective consciousness, many otherwise separate component, biological or otherwise, which can come together and form a sentient mind?

Is it possible that humans are only at the top of the biological food chain? Is it possible that there are other parallels, achieving equivalent or even higher intelligence? Is it possible that we coexist on Earth with a parallel non-biological chain of life?

If biology is not necessary for conscience, then how does that affect the Habitable Zone?