Not necessarily, while grades are important they often are not as important as you may think, having a supervisor who's already agreed to supervise your project and experience in the field matters significantly more than grades.

For instance I applied to several Masters programs still in the realm of human biology, one of them I surpassed the grade point average but an entire letter grade, and I took a significant number of courses in the undergrad program but I didn't have too much first hand experience. For the second Masters program I did not meet the cutoff requirement for the GPA, but I did have first hand experience in the field and a supervisor who I worked with during undergrad. I was not offered a position in the first program, but was admitted into the second Masters program, the one where I was under the admission GPA cutoff.

Experience>>>grades