Hi Naresh,

Biology questions are not asked in any separate section in NDA Exam. There is a section called General Ability Test (GAT). In that section there are two parts, part A and part B. In part B, there are almost 10 questions from General Science that are likely to be asked from biology subject.

Refer here for more info - https://competition.careers360.com/articles/nda-exam-pattern#NDA-Exam-Pattern-2020-for-General-Ability-Test-GAT

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!