CBSE 12th

Hello Sajas,
A wide range of options are available for students after 12th grade in India. Since you wish to stay in the field of Biology / Science, these are some courses that you can look into.
1.Biomedical Engineering or Biotechnology Engineering. Engineering in the field of Biological Sciences is a relatively new and exciting interdisciplinary field. The industry is fast growing in India and abroad, with various opportunities available after undergraduation. Apart from these 2, programs likeEnvironmental EngineeringandAgricultural Engineeringare also available in a selected few institutions. All B.Tech programs are 4 year courses unless you opt for Dual Degree programs in places like BITS, IIT, etc which are for 5 years.
Since these courses are nothing like B.Tech in Computer Science or Electronics (mainstream), it is highly recommended that you join a REALLY GOOD college if you opt of these courses.
2. A Bachelor of Science degree if you are particular about wanting to pursue pure sciences. There are many B.Sc degree options in the field of Biological Sciences like,B.Sc in Biology, Microbiology, Genetics, Biotechnology, Zoology, Botany, etc. This program is for 3 years and is usually taken up with a M.Sc degree after that for 2 more years. It is highly research oriented (B.Tech is application / job oriented) and you should be prepared to spend your years in the field of scientific research.
3. A 4 year BS Programme at IISc. If you really want to aim high in this field, this is what you should be aiming to get into. It is a newly introduced undergraduate programme at IISc and is created to be on par with the 4 year BS undergrad courses available in countries like the USA. The courses are structured in a similar fashion, and what more, you get to do your internships and research under some of the best professors and students in the field of pure sciences!
4. A Bachelor of Pharmacy course. The Pharmaceutical industry is one of the richest industries in the world, with billions of dollars being spent on Drug Discovery, Toxicology, Delivery, and other R&D every year. One usually tops it with an MPharm course to get into the industry as a research scientist, or an entrepreneur. Many new pharmaceutical companies are emerging around the world with the increasing application of computers and technology in the field.
5.IISERs also offer good options for studies in Biological Sciences.
All the best.