Hh, sorry I know this was like months ago when you commented. But I wanted to say that Bisexuality isn't just correlated onto Male and Female, it's two genders on the spectrum you like. It can be Females and Males, or Agenders and Males, etc.
Pansexuality is used to say that any gender of the spectrum you accept, and are not limited to two. They're sister sexualities in a sense.