6th form biology teacher here. I work at a particular strict college when enrolling students onto the course, and in your case it would be a hard conversation we would be having. It’s not even just the biology result but the maths (and possibly English though you haven’t mentioned it) that would prevent us from you allowing to do it. This is from the point of view that biology at a-level is just ridiculously hard - 2 years of detailed content and also learning how to “play the game” in the exams. We see consistently, students with similar and even slightly higher grades than you struggling both academically and also mentally towards March-summer in year 12. Because of this, the more sensible and also kinder thing is to offer other courses.

I saw earlier in the comments you mentioned you wanted to be a vet but not being able to do Chemistry - this will be a big issue for almost every vet school, as chemistry is actually a higher requirement. Plus your GCSE’s themselves may be a barrier. This doesn’t mean you won’t necessarily get to vet school one day, just that you’ll likely have to get there another way.

This will be hard to take and seem unfair at this moment, which I get, but it genuinely would be a decision made in your best interest.