I understand the argument you're making, but it feels misguided in my opinion. Other things don't need consciousness to be valid -- and more importantly, consciousness is not an inherently positive thing which needs to be extended other things. Ideally, consciousness is specifically defined such that we can draw relatively clear boundaries between what is conscious and what is not.

In any case to answer where consciousness comes from, consciousness arises from the brain. You can test this with anesthesia, which is markedly different from sleep in that it does remove conscious experience. Although I agree it would be hard to pin down exactly what spectrum of animal is, or is not conscious, I think the extremes are pretty obvious. Obvious, unless, you're trying to extend consciousness to anything which could sense and react to its environment. If you want to call that consciousness, that's fine -- the human experience of having a distinct identity which can feel self-conscious, proud, content, anxious, etc -- is then something different entirely.