It will depend on the university and the specialization whether you need to appear for an entrance exam to get admission into a B.Sc. program. Most of the good institutions, such as Delhi University, Mumbai University, and so on, give admission based on Class 12 marks through merit. However, for specialized B.Sc. courses like Biotechnology, Agriculture, Nursing, or Hospitality, you may need to appear for an entrance exam, such as CUET, ICAR AIEEA, or state-level exams.
Private universities and deemed institutions can conduct their entrance tests or even grant direct admission on merit. Highly competitive universities like IITs for B.Sc. Data Science and IISc require stringent entrance requirements. If you target a very top-ranked institution, then preparation for an entrance test is a must. Check the admission criteria of your targeted college before joining it to see if you meet all the criteria. Understanding the process will help you decide whether to focus on entrance exam preparation or rely on merit-based admission.