Dear Swarnendu,

After doing B.Sc in zoology, you can apply for appearing in IIT-JAM Biotechnology(BT) for pursuing M.Sc in Biotechnology, M.Sc-Ph.D Dual Degree in Environmental Science and Engineering or Joint M.Sc-Ph.D in Molecular Medical Microbiology. Each degree can be pursued in a different IIT. For joining these programs, you have to appear for IIT-JAM exam which is conducted by IITs and IISc every year. In 2019, JAM was conducted on Feb 10 by IIT Kharagpur. Next year, the exam will be conducted by IIT Kanpur. Keep checking the official website for latest updates. For more information regarding syllabus, eligibility criteria,etc. refer https://jam.iitkgp.ac.in/?id=p&n=100