Hello Science Tech

hope you are fine and doing good

As per your query , I would advise you in your case you dont need to worry at all. Its happen with many students that they suddenly want to take bio for increasing options in entrances like NEET and making percentage on a safe side if marks in one subjects comes low. You just need  to write the application to the concerned authorities that you are interested in  BIO and kindly add it my couse circulumm and problem will be solved easily as in 5 days not a large part of syllabus is covered

Hope you found this answer helpful. Good luck for your future