Looking to Genesis to debate the science of life on this earth seems to be missing the point to me. It implies that the stories there are presented as an alternative to modern science. It ignores THE FACT that this is an ancient text, written by and for ancient people (under God's inspiration). It is a failure to listen to what is being communicated.
So revelation says that humans are in a position of responsibility in relation to the world. Genesis 1 seems to imply that it may be a struggle (subdue and have dominion). There is a parallel to the idea of God ordering the universe to subdue chaos. Humans have a battle on their hands keeping the world under control. Human choices were meant to make the world a better place. In Genesis 2 the language is less aggressive and combative, The man is a laborer who watches over, protects or keeps the garden. But once again there is an implication that all is not well, why else must the man watch and work? So from the beginning there is a deep sense of human vocation to work and even to struggle.
The question is "what is up with the tree?" Knowledge, in the biblical sense, includes experience. That is why "to know" is a euphemism for sexual intercourse. The knowledge of good and evil is not merely theoretical. There is a sense in which one must experience evil to know what it is. Knowledge is also understanding. It is the ability to think deeply into things. There are lots of explanations about the tree. I am sure that the tree was a multi-layered image even from the beginning. But whatever else it may represent, it is clearly a symbol for limits. In the garden, man (and woman) had all that they needed. They were provided for and they were occupied. But there were limits. True freedom is dependent upon our ability to choose to do the right thing. Obedience makes us better, it grows us and allows us to become disciplined, trustworthy and faithful.
Personally, I do not think that the tree was any different from any of the other trees. What made it a tree whose fruit gave the knowledge of good and evil was the simple fact that God said do not touch that one. Once it was forbidden it changed. Once a hand reaches out to touch this fruit, to take and eat this fruit, then the human person would experience and know doing evil. Being disobedient instructs us. Once we learn that we are not to be trusted it will effect our view of ourself and our view of others. Those who know the story know that Adam and Eve experienced shame (they saw they were naked; i.e. they experienced a need to "cover up" as they became more self centered and self focused) and shame led to blame (relational break down and finger pointing. Adam blames God and Eve: the WOMAN that YOU gave me, Eve then passes the blame to the snake).
I also think it is a micro-version of the history of Israel. They are in the promised land, sin, and are exiled. The story of Adam and Eve is also our story. We ruin it all by our choices and then seek to blame everyone else. Yes, this is a deep narrative told in simple form. And it is True. Truer than those who would reduce it to debates about biology. I will write about evolution later.