I personally don't think high school marks are indicative of what you will or can get in university. If you really put your mind to it, you CAN achieve high marks! Never mind that other students going into life sci may be walking in with a high average. As mentioned before, this just means they've developed some sort of studying technique to achieve those marks in high school. The reality is though, those techniques will drastically change once you enter university. I almost feel like everyone gets a fresh new start in university. You have to tweak your studying habits and techniques because what may have worked in high school may not work in university (which is exactly what happened to me).
Honestly, keep up with the readings and the work load. Don't fall behind. Of course, make sure to take some time for yourself but make sure to utilize all the resources university offers! Go to office hours if you need help - don't wait till a week before the midterm to get your questions asked. Ask questions in class, get to know other peers in your classes/tutorials/labs so you can form study groups and help each other out!
I just want to re-iterate that everyone pretty much starts on a new playing field when getting into university (in my opinion). I've seen people do complete 180's - in high school someone i knew was pulling off really low marks but got relatively high marks in university once they buckled down and realized they wanted to change.
You can do it!! breathe
and enjoy your university experiences! Hope this helped