"Are there bears in Scotland?"
Translation:A bheil mathain ann an Alba?
In both your examples there is the preposition "in". The difference is that "ann an" is the preposition "in" used where there is no article (in Gaelic) and "anns" is the preposition "in" used in front of the article. The confusing thing is that the "an" in "ann an" looks like the Gaelic article but it's not, it's simply a part of the preposition. You might ask why then is "ann an" written as two words. Search me. Some historical reason I guess.