Yes. The candidates who have completed B.Sc in Biology are eligible to apply for CDS Exam.

But the thing is they are not eligible to apply for all the defence services through this Exam.

Here is the complete information in regarding to that.

Every year UPSC (Union Public Service Commission) will conduct CDS Exam twice a year to recruit the candidates into following defence services
Indian Military Academy
Indian Naval Academy
Indian Air Force Academy
Officers Training Academy

As you don't have Mathematics subject in your Graduation, you are eligible to apply for IMA and OTA.

To apply for IMA, the maximum age limit is upto 24 years and for OTA it is 25 years.

The nationality of the candidate should be India to apply for this Exam.

As you are pursuing your final year of B.Sc course, you can apply for this exam once you have done with your Graduation.

Have good preparation for this Exam and crack it.

No minimum percentage of marks are required for the candidates in Graduation to apply for this Exam.

Wish you all the best.