Yeah, they will. To be frank, I think you're stressing too much about this, which is normal for someone who is just starting out at uni (I was the same as you). As said previously by others, 95% of the time for bio labs, you will finish early, sometimes even an hour early for some courses, therefore giving you enough time for a break. In some bio courses, a tutor may even offer an hour during the week for those who missed out on their scheduled lab to catch up on stuff they missed. You could also find a buddy in bio who isn't doing chem to write up notes for you or to just give you the answers. Also, from my experience, most of the questions in your bio prac book can be answered through research on the internet; the prac is only for hands-on experience, in my opinion. In fact, answer as many questions as you can in your prac book from research on the internet before the lab, and I'm sure you'll finish way early for maybe even a 90 minute break.
OK, I don't know what happened there, but my gut feeling says that you over-analysed it. Perhaps the bloke was really lost (he's old), or maybe he is a lonely chap and just wanted someone to talk to. Or he might be a divorced dad who has children that don't contact him anymore, and maybe you just remind him of one of his daughters who he misses. Who knows? From my experience, especially in Campbelltown, old people are really nice, and never molesters (only those oafish 30-50 year old blokes are, I reckon, and they are rare and mostly drunk when doing really stupid s&?%). I've had some really wonderful conversations on the train with old people--they are really nice people who just want to have a chat. In my opinion, if he isn't touching/groping you in any way or asking you about your romantic life, just have a friendly chat with him (I'm pretty sure he only asked you about school or your career aspirations and something like that). I'm not having a go at you, by the way--maybe he was being really creepy on you and was hitting on you romantically--but it just seems weird for an old bloke with white hair to be trying to seduce a young woman. Old people are usually very gentle and kind.