No cell or neuron by itself is any more or less aware than another so no combination of it makes us "more" aware. With emergence it is the complexity that gives rise to self awareness, not that any human neuron is more aware than neurons of other animals.
I've moved this up as it is so vital.
Interestingly enough, within the human brain itself, some neurons are vastly "superior" than others. Just like certain brain regions have more to do with awareness and consciousness, so do certain types of neurons. Cortical neurons such as Purkinje neurons make all the difference in the world. This is because pyramidal neurons in general but those in the cortical regions especially are unbelievably complex. Cognitive abilities in animal species is not just a matter of brain size or number of neurons. Rather it has a lot to do with specific areas of the brain (cortical regions in particular) and how much the neurons in such regions are able to received input from sensorimotor regions.
When a single neuron can receive input from a few hundred thousand other neurons, and when you have a lot of these in areas devoted to integrating information from sensorimotor regions as well as the interactions between the cortical neurons themselves, it means that there is absolutely a difference in the types of neurons in a brain. The shape of a dendrite, the way that a dendritic tree branches, and a large number of other factors make some neurons capable of contributing much more to higher cognitive functions that others. No other animal known has anywhere near the complexity of the regions associated with such functions. None are capable of our ability integrating information from different regions because none have the types of specific neurons that are incredibly important for this process the way that humans do.
Recall that the emergent "hive mind" of the ants required that there be a certain number of ants and certain types of ants. There is a BIG difference between the emergent "hive mind" and the human mind (or a dog's "mind"). This is because even though there are a few different types of ants in a colony, each ant can "connect" only to ants that are in close proximity to it (in time and/or space). So for ant colonies, the right number is hugely important, because most of them are basically the same.
That's not true of neurons. A single neuron can be connected in millions of ways such that a small region of the brain is more complex, more connected, and processing information far greater and faster than an entire colony of ants.
Different cell structures of neurons are vitally important.
I wouldn't define consciousness that way but with defining awareness there is a bit of wiggle room.
There's actually less.
You might find these reviews of change blindness and attention worth reading.
Change Detection is the longer one, but it is still less than 30 pages and it is a good review of awareness studies.
Change blindness: Past, present, and future is shorter but misses a lot of stuff may even be more difficult to read.
We have run experiments on awareness from rats to humans for ~70 years. We have no such history of research on consciousness that even begins to compare.
That is because things like single celled organisms exhibit attributes of being aware of its environment and it is the emergence of these cells, which are also present in plants and insects, that gives rise to cognition.
You are equating reactions with awareness. Being unaware usually means not reacting. If you're in the middle of a conversation and don't hear the phone ringing, you are conscious and you are aware of e.g., the person you are talking to, but you are not aware of the phone ringing. So you don't react.
When e.g., a plant or cell can only react, then we know that they aren't aware. We have defined awareness in terms of attention, cognition, short-term memory, and all kinds of things we can test using experiments (including neuroimaging studies). We have good definitions that help us to understand everything from evolutionary processes to learning and memory (and how these relate to perceptual faculties).
Our self awareness must be harnessing this low level awareness somehow
Why? Plants, like all living things, require energy (fuel to keep them going). Should we assume that all living things use photosynthesis? No. More importantly, we have that low-level awareness: autonomic nervous system. If you accidently put your hand on a hot surface, or eat food that is way to sour, or any number of ways people automatically and unconsciously react all the time, you can compare this with the reaction that plants and cells have: a purely unaware reaction that the system has no control over at all.
We know the kinds of things that humans will react to in much the same way plants and bugs and so forth do. We can knock out genes in mice and make them incapable of being aware of certain things. There are disorders humans have that make them unable to react to pain (which is extremely dangerous) or which cause sounds to be interpreted as colors. We have spent decades studying the perceptual system and the conditions in which a person will be aware of X but not Y.
In order for us to function the brain must be aware of a lot more than what we are consciously aware of so there are other things to be aware of besides what we know about.
Think about all the things you or people you know do that they aren't aware of. Maybe the cat just broke a vase and you put down your class without being aware that you did this, and so you can't remember where you put it. Maybe in a rush to get to work, you grabbed the wrong set of keys. The things that we do all the time without being aware are all the ways in which we react unconsciously. Awareness requires the ability to perceive (through sight, sound, both, etc.) and to direct attention and cognitive resources to something (a lecture, a book you're reading, a forum post that is way too wordy, etc.), and also the ability to do things without being aware.
Reaction is being unaware.