The layers don’t stop because you choose one: you are biological, because you’re chemical, because you’re physical (which is more like saying you’re electrical).
Ie. Laws of physics govern the laws of chemistry and the first couple are chiseled in stone for the most part. Biology, that is to physics what psychology is to surgery (perhaps mathematics is a batter analogy).
You can’t choose that you are ‘just’ biological because it is the emergent property of deeper systems of rules.
Consciousness, now that is a debate for the philosophers.