[trumandogz]

In my Constitutional Law class, the subject of 'naturalized citizen' came up and the professor wondered openly to the class why the founders put that in there....

While I am not a professor of Constitutional law, I am pretty sure that the term 'naturalized citizen' is not in the Constitution.

I would be quite dubious if your professor's open wonderings.

[Non-Sequitur]

While I am not a professor of Constitutional law, I am pretty sure that the term 'naturalized citizen' is not in the Constitution.

Indirectly. The Constitution says that Congress will establish a unified rule of naturalization. Naturalized and natural-born are the only two forms of citizenship identified.