B Zhang

A survival curve looks like the profile of a crowd walking down a long corridor: at first everyone is together, then some fall behind, and finally only a handful remain. If the corridor ends in a steep cliff, the crowd falls almost simultaneously, which on a graph looks like a rectangle. If the exit is a gentle, long slope, people leave gradually and the curve stretches into a triangle.

The liver is an orchestra in which every cell plays its part from a shared score. Males and females have different scores: in males, the genes responsible for detoxifying foreign substances and steroid hormones sound louder, while in females, the genes for fat metabolism and bile acids do.