Yes you can do Bca even if you have biology as your subject.  Some colleges do take admission according to Maths marks only , but some colleges allow non maths students too. BCA is related to computer , so for you it may be littel difficult as you have studied Biology.  If you have some basic knowledge  about computers then you can join Bca without a doubt . If you have mathematics as your extra subject and if you have scored good marks in it then you can join Bca without a harsh in top colleges. 

Dear Student,

BCA is a 3-year UG course that deals in basics of computer applications. The course eligibility is 10+2 from a recognized board with minimum aggregate marks as per the institutes’ requirement. BCA course graduates have a variety of career options after completion of the course. Apart from pursuing higher study course such as MCA or any related course, students can secure a job in diverse areas such as software development, banks, ITES, government departments, Education, etc. One can become Programmer, System Analyst, Network Designer, System Manager, etc.  and earn about Approx. Up to INR 2 to 20 Lacs per annum. So, yes you should go for it.