Consciousness ad Sentience

 I have concluded that consciousness is unique to everything that lives and that it is the result of brain activity.

Consciousness is generally defined by philosophers as our ability to be aware that we are aware, that we can think about our thoughts while sentience allows for feelings like pain, pleasure, fear, joy, etc. and emotional integration. So, they exist separately but dependently in the mind. Causality can be seen to work herein. For example, a felt pain (sentience at work) will produce a thought to act (consciousness at work) to reduce or eliminate the pain and plan how to avoid it in the future. Now we pretty much know through experience that this is how the Homo Sapien mind functions. How, though, can we know which animals, plants, insects, and AI possess consciousness and/or sentience? Again, we know from experience that most animals have some degree of sentience. When harmed physically, they react. As much as we would like to believe it, we cannot know if they are aware that they are aware. Higher order plants have also been shown to react to physical harm. Insects, I don't know about but expect that they, as well, have some degree of sentience. Even single-cell organisms appear to move to avoid harm. The thing is animals, plants, insects, and other organisms do not demonstrate or communicate their degree of consciousness, if any. We simply don't know. AI, as far as we know, has not yet achieved conciousness or sentience. If it did, would we be able to recognize it? We don't even know what human consciousness is or how it is developed.