Hello asirant,

A Biology student can not apply for B.tech . To get Admission for B.Tech you must have 10+2 with Mathematics and Physics as compulsory subjects.
With Biology, Chemistry, and Physics at 10+2 you can opt for career in Life Sciences. If you are choosing career in Life Science, then some of the courses that can be considered for graduation are: 
Bachelor courses (B. Sc.) in core Life Science subjects, that include specialization in Zoology, Botany, Geology, Microbiology, Immunology, Biochemistry, Biomedical engineering, Genetics
Bachelor courses in Applied sciences: Biotechnology, Forensic Sciences and criminology, Bioinformatics.
Bachelor course in Pharmacy (B Pharma).
Bachelor of Science in Agriculture: Agricultural Meteorology, Agronomy
Bachelor of Science in Food Technology
Bachelor of Physiotherapy

Hope this will be helpful...