Hi

No, it is not mandatory to pass in your additional subject or optional subject or your 6th subject in your board examination

This is because,

Even if you fail in your additional maths subject you will you be still pass in your board examination in overall, provided you pass in rest of the 5 subjects and you will be eligible for taking admission in graduation.

Now that, you want to pursue your BSc in biology i. e bsc zoology/botany etc

For reference, eligibility criteria in Delhi University is provided below :-

*B.Sc (Hons.) Anthropology/ Biological Sciences/ Botany/ Microbiology/ Zoology:- to be eligible you must have passed your 12th board examination and must have got at least 50% marks in English and at least an aggregate of 60% marks in PCB i. e Physics, Chemistry and Biology or Biochemistry or Biotechnology .

So, it doesn't matter even to fail in your additional maths examination you will be still pass in your 12th board exam and will be able to take admission in graduation provided you meet rest of the criteria required for admission

Thank you