2. Why is probability useful in biology?

It gives you the idea of what might happen (a mom has the allele pair Bb and dad bb; probability for the child to have the Bb allele is 50% and bb allele 50%)

Probability is the chance that a certain event will occur. For example, the probability of a head turning up on any given coin toss is 50 percent. Probability can be used to predict the chance of gametes and offspring having certain alleles.