Hello aspirant,
As per your query Admission criteria in Madras Christian College for B.sc biology and plant biotechnology is MERIT BASED  but for various other courses it may be merit based or entrance based (MCA).
Applicants for B.Sc must have minimum 50% aggregate marks with mathematics, physics, and chemistry in higher secondary examinations or equivalent.
The Application form commence date is May 16, 2019.
Hope it helps,thank you.