Yevamot 40: Inheritance Rules: A Key Element of Yibum

First, a timely comment on chametz on the altar, and matzah too, for that matter, for an episode release after the first day of Pesach (as that day's daf). Also, what is the goal of yibum, what is accomplished? Plus the implications for inheritance. Also, how doing chalitzah has impact on other potential relationships, prohibiting some relatives of each to the other.