Science Assessment

Which of the following correctly describes what happens when a population of bacteria becomes resistant to an antibiotic?  Note: a bacterium is a single individual in the population of bacteria.

1. During treatment with an antibiotic, each individual bacterium tries to become resistant to the antibiotic. Only some are able to become resistant, and these individuals survive to pass this trait to their offspring.
2. During treatment with an antibiotic, all of the bacteria gradually become more resistant to the antibiotic the more they are exposed to it.  They all survive and pass this trait to their offspring.
3. During treatment with an antibiotic, a population of bacteria usually dies.  Sometimes by chance, all members of the population become resistant at once, survive, and pass their resistance to their offspring.
4. During treatment with an antibiotic, only those individual bacteria that already have a trait that helps them survive the effects of the antibiotic will live.  Their offspring in the next generation will also have this trait.