Hello,

Yes you can take Biology as additional subject which will be optional from a list of options. There will be other option like IT, electronics, Biotechnology, geology .. etc.

from that list you can take biology as your optional subject. keep PCM as your academic subject as Physics,Chemistry,Mathematics is required and make you eligible for many entrance exam.

There is end year exam for the both year. so there is end exam for 11th and you will qualify for 12th. end  year exam for 12th will be your board exam. There might  be some minor change in the usual process which will be notified by your 12th board where you will join.

Hope it helps!