Hello student no it's not mandatory to have a graduate degree in Bsc ZBC.

As per eligibility criteria student should be graduate with one of the following subjects to be eligible - Chemistry, Botany, Animal Husbandry & Veterinary Science, Geology, Mathematics, Physics, Zoology and Statistics.

If you hold a bachelor degree in any one of the subjects mentioned above then you're eligible for UPSC IFS.

Age eligibility - Minimum 21

Maximum 32 (General category)

Feel free to comment if you've any doubt

Good luck