This silent animation created for Evolution: "The Evolutionary Arms Race" follows the progression of antibiotic resistance. When a sick person takes antibiotics, the drugs begin to kill off the bacteria. But if treatment stops prematurely, it leaves some microbes alive -- the ones with mutations that make them resistant to the drugs. As these survivors multiply, they pass along their protective mutations to all their descendants. In this way, the bacteria evolves into a new drug-resistant strain.