1. What is euthanasia? Why is this issue a controversy?

2. What is overspecialization? Why is this a problem?

I only can give an answer for Euthanasia. Sorry.

Euthanasia is the act of mercy killing. Killing for the betterment of that person. (to end the suffering mostly)

It's a controversy because it is about life and death. It's not natural, though it is for the betterment of that person, everything about it, the act of killing or assist in killing goes against our innate sense of moral. It's an ethical dilemma.