The experiment investigates the survival of Caenorhabditis elegans host populations when exposed to a bacterial parasite, Serratia marcescens. Exposed host populations were either large (500 individuals) or small (25 or 50 individuals) and were either susceptible or resistant to the disease. Populations of C. elegans were evolved against either heat-killed or live bacteria. After 13 generations of host evolution, we exposed the worms again to the bacteria to determine whether the worms lost, gained, or...