Not to be drawn into the debate but I think the serpent in genesis is literal not symbolic. As we now know, satan can use anything or appear as anything even disguised as a person.
Mya, that's true. He can do that.
Yet it is narrated that God punished the serpent (the animal) by making him crawl on his belly. It is understandable that Adam and Eve could've been fooled by Satan's disguise, yet the same cannot be said for God. But if you read that literally, then it seems like God does not differentiate the animal from the tempter. I am therefore disinclined to treat that literally, but instead figuratively.
Remember, Genesis doesn't really tell us that it was Satan anywhere. This is something that has universally been understood regardless, that the serpent is the devil, who is called the deceiver and the tempter all over the scriptures. That tells me this was a symbol that everyone understood to be a reference to Satan as a tempter of humanity and not a literal occurrence involving a real snake. I see it the same way I see the dragon in revelation. These are generally symbols for Satan. St Peter also compares him to a roaring lion roaming the earth seeking whom he may devour. So satan is compared in many ways to animals deemed dangerous by the human psyche.
The punishment to crawl on the belly seems to represent some kind of punishment or curbing of his powers by God; some way that his leeway in man's world is diminished as a result of his causing man to fall.
Even the proto-evangelium--the curse God uttered to the serpent--has been historically interpreted to be a promise of salvation to Adam immediately after the fall of man. So God says "And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel" (Genesis 3:15). That clearly announces the coming of Christ who will crush the serpent's head. After all, he may have lost his legs but yet he still roams free and can even "bruise the heel" of man still.
The tree of life is unmistakably a symbol for Christ, the bread of life, and Christ speaks of himself in the identical terms in which the tree is described, "eat and live forever".
The tree of knowledge of good and evil represents some kind of independence from God, which is why Adam is told not to eat from it. Eating from it means deciding good and evil for oneself instead of placing filial trust in God as one's Lord. It's basically the essence of rebellion, or desiring/becoming one's own God.
So for me, and I understand for many early church fathers, the story of the fall as narrated is not a literal story but a symbolic narration of the fall of Adam and Eve from grace.