Learn about the math behind predator-prey population cycles in this video [4:28] from NOVA Digital. In this example, zombie and human populations fluctuate. The zombie population increases as zombies convert humans into zombies. However, without enough humans to eat, zombies die and the population shrinks. The human population increases as humans reproduce but decreases as zombies eat humans. The populations of humans and zombies change through time according to a pair of differential equations. Because human and zombie populations are related, the growth rate of each population depends on the current numbers of both humans and zombies. Zombies and Calculus, Part 1 - Discussion Questions are provided.