I think there may be a little bit of confusion here. A standard B.Sc. is a four year degree. Co-op programs that involve internships either have the students working over the summers or extend the program to five years.
Also, a master's degree is a graduate degree. Normally this takes about two years to complete after completion of an undergraduate degree. There are some programs that naturally extend undergraduate work into a master's degree for a fifth year. There are more popular in Europe, to my understanding.
As for careers from a "human biology" degree - biology in general is a fairly popular major, but it's not a professional degree. So you won't necessarily find positions that look specifically for that degree. Rather, it will be a stepping stone. If you want to get into academia, you'll have to do graduate school. If you want to do medicine, you'll have to go to medical school. You can use it to get into other medical areas too: physical therapy, ergonomics, health work, for example. A lot will depend on what you take within the progam itself. For example if you take several statisitics courses then you could open up career options in fields like data analysis, market research, and epidemiology.