if you have the following courses:

Physics
Biology
Chemistry
Calculus
Psychology

I don't think there is a number per se. However, if your overall average dips beyond a certain point (I believe a 3.0 on Mac's scale) you'll be put on academic probation. If you don't raise it by the end of the term you will be kicked out of Mac.

If you fall below a 3.5 cumulative average (cumulative, not sessional), you will be put on academic probation for one year. If you can`t get your CA up overthe 3.5 mark after that year, you`re cut.

Depends on the Faculty as well. I know for Commerce first years you cannot fail any required courses or else you are removed from the faculty.

But from the courses you are taking, it looks like your in the science faculty. I do not know if the faculty has any other requirements than the MAC ones.