yes destoryer bio is random. also there is no real distribution on them. you will get blatantly obvious questions in succession, followed by completely random difficult ones.
the randomness part I guess similar to the dat. Biology is a broad subject. they probably have a pool of thousands of questions they can ask you.
as I mentioned in my breakdown, one of the answers to a question i got wrong is buried in Campbell's Biology. It was a tiny little blurb, only a sentence long.
my best advice over the next 3 weeks is not only know the right answers but know what the other choices wrong and what they actually mean.