This activity is a hands-on simulation using Skittles and mini-marshmallows to show how natural selection can act as a mechanism to increase the presence of antibacterial resistance in a population. Students simulate the effect of hand sanitizer on a population of bacteria, collect, record, graph and analyze their data. The bacteria that are affected by the selective pressure decrease and the population of bacteria evolves to be one that is largely populated by bacteria that are unaffected by the selective pressure. To begin the lesson students are given background information about natural selection and discuss how this can relate to their lives. Then students are given Skittles and mini-marshmallows and simulate the effect of hand sanitizer on bacteria. Since most of the “bacteria” are soft marshmallows they are caught more easily by a toothpick (the hand sanitizer) than the hard shelled Skittles. After a specified period of time the round ends and the remaining “bacteria” reproduce by fission for the next generation. The process continues for three generations. Possible follow-up lessons include watching videoclips and reading about antibiotic resistance having student role play scenarios to illustrate how antibiotic resistance happens in our world.