Hello,
Yes, you can appear for the exam even if Biology is not your subject, but it depends on the exam rules and the course you are applying for. In some entrance exams, all subjects have sectional minimum marks, so not attempting Biology may reduce your chances. If the course requires Biology, then minimum marks in that section may be compulsory. If Biology is not required for that course, then it may not affect admission much.
You should check the official brochure of the exam to confirm the subject requirements and minimum marks criteria.
I hope this helps you.