"This is a biology laboratory."
Translation:Bu bir biyoloji laboratuvarı.
I think you have to break it down as "a laboratory of biology" to understand that here, biology counts as a noun. That's why it's "biyoloji laboratuvari", with the "i" at the end of "laboratuvar". If it were an adjective, it would be "biyoloji laboratuvar" (as in "küçük laboratuvar"), but apparently it doesn't work like that.