The genes to be resistant to an antibiotic already exist in the bacteria's genes. Those whose phenotypes are resistant to the antibiotic will survive the antibiotic which kills the other non-antibiotic-resistant bacteria. The surviving bacteria will then asexually reproduce, producing more antibiotic-resistant bacteria.
Answer;
Mendel's work was not well known until many years after Darwin published his theory of evolution
Explanation;
-Mendel's work was ignored because it was not widely distributed, and he didn't make an effort to promote himself. In actual fact, the reasons are more complex.
-Gregor Mendel had the answer to Darwin's problem. Traits were not blended, but inherited whole. And according to Mendel's laws of inheritance, a trait that might disappear in one generation might reappear in the following generation. Modern Neo-Darwinism combines both Darwin's and Mendel's work.