Question

Several bacterial colonies are placed on a petri dish that contains agar with antibiotics. After 24 hours, ninety percent of the original bacterial colonies die, but the remaining ten percent survive and later reproduce. Which of the following theories is demonstrated by this experiment?

Answer 1

The theory that is demonstrated by this experiment is natural selection.
Basically, only the strongest bacteria survived, and nature decided which of those bacteria were fit enough to get to live and reproduce in the future. Those bacteria that were "willing" and able to fight their way through a huge number of bacteria were the ones who ultimately won.