What sacrifices do people make to ensure their own or someone else's survival?

In cases where we are talking about ensuring survival, we can assume that lives are at stake. This means that people will behave in extreme ways.
The idea of a "sacrifice" suggests selflessness, and indeed people will sometimes behave selflessly in order to protect their loved ones, particularly their children. There have been many recorded instances of parents sacrificing their own lives so that their children can live, from the sadly mundane—women choosing to give birth to their children under dangerous circumstances, knowing they are likely to die in the process—to the disastrous and unexpected. When a child can only escape from a home made unstable by an earthquake if a parent steadies the building for them, parents have repeatedly sacrificed themselves to secure their children's escape. Where there is a limited supply of food or water, parents will sacrifice their own share for their children. This is a natural instinct.
Arguably, however, parents' overwhelming need to provide for their children can be selfish, too. If there are two children and enough food only for one of them, will a parent feed their own child over someone else's? Often, yes.
In the same way, what we will "sacrifice" to save our own lives, where no loved ones are involved, is sometimes selfish, too. People sometimes sacrifice their moral compass, choosing to make decisions which result in someone else dying first. Or we may sacrifice the laws of society: in order to survive, humans have resorted to cannibalism. Humans have also tried to ensure their own survival by sacrificing parts of their own bodies, as when the climber Aron Ralston amputated his own right arm with his pocketknife in order to escape a rock which was trapping him.
So, humans have been known to sacrifice both selfishly and selflessly in order to ensure the survival of themselves and their families. What precisely is sacrificed depends on the extremity of the circumstance.