Firstly this is kinda not feasible. Actually I guess you could do it , only in a way that would mean you have a limited and inadequate understanding of the course.The bio course is quite extensive and you do require understanding and sometimes some rote learning.
Just as everyone else has said , if you are going to do it , do it properly.I was planning to do the whole unit 3 , but only ended up finishing AOS1, which kinda sucked because AOS1 is basically revision of year 11 bio.
Re :difficult concepts in bio
This is a list of things that I struggled with :
-immunity
-genetics (I kinda struggled with this initially but once i got the idea , it became pretty straight forward. )
-human evolution ( only cause I hated the topic and it entailed a lot of memorising , which made it more boring.But, as in every topic there are stuff that u need to understand in this topic.Also , the study design dot point for this topic is quite ambiguous , well in my opinion )
-immunity
-did I mention immunity ( k maybe I over exaggerated this , but it was something that took me forever to understand.And it was only after some amazing ppl on the bio thread explained it in a simple manner that I understood it )
And , I know u have probs heard this a million times but pls do have a break too.I wish I had enjoyed my holidays more.
Anyways good luck and enjoy bio( it is amazing )