Darwin hypothesized that there are definite steps to natural selection. consider the model of bacterial resistance to antibiotics. use the roman numerals (i - iii) to guide you through the steps to describe how darwin would explain antibiotic resistance. a) there is a change in the environment: an antibiotic is added. some of the bacteria adapt to the new environment. they survive and reproduce. b) in any population, variation exists. some bacteria are resistant to antibiotics. most bacteria die, but the bacteria that are resistant survive and reproduce. c) sexual reproduction of bacteria cause variation. some bacteria survive antibiotics and some do not. regardless, over time all of the bacteria should become extinct. d) in a population of bacteria that are exposed to antibiotics, some bacteria are able to change their genetic make-up and survive. the new genotype is passed on to offspring.