Hii aspirant..

The Indian Air Force basically comprise of the following branches:

• Flying Branch
• Technical Branch
• Administrative Branch
• Logistics
• Accounts Branch
• Meteorological Branch

Now, specifically for a graduate in Biology, there isn't any particular branch but being a graduate, you may apply for the Administrative Branch as well as for Logistics, provided you have scored a minimum of 60% in the bachelors degree examination. To get into any of the two branches, you will have to write Air Force Common Admission Test which is conducted twice a year by Air Force Selection Board. Apart from these two branches, you may also be considered eligible for the Flying Branch provided you have studied Physics and Mathematics in the +2 level. The entrance examination for the Flying Branch of Indian Air Force is conducted by Union Public Service Commission, known as Combined Defense Service Examination 

Hope this helps. 

Best of luck.