The bacteria which had mutation became resistant to the antibiotic and survived and keeps on increasing, promoting natural selection.
Explanation:
The bacteria rapidly divide, the chances of mutation in the gene increases manifold.
The strains of bacteria causing tuberculosis and staph infection got mutated at DNA level such that they became resistant to antibiotics when tested those susceptible did not survive. These mutations were not harmful to bacteria and the resultant bacteria survived.
These bacteria which survived and proliferated as the environment was in their favour.
Thus, Darwin's Theory of Natural Selection is acceptable here as it says if a mutation is occurring towards the increase in population, they will be selected ones.
