Rapid reproduction in bacteria leads to rapid mutations and thereby they cause evolution to occur.
Step-by-step explanation:
Bacteria are the organisms that can reproduce as early as 20 mins in this universe, when every organism reproduces it does make small changes in the genetic make up so as to survive through the evolution.
Thus when a bacteria reproduces in 20 mins in about 1 hours nearly 2 positive mutations happen thereby causing them to evolve quickly . This is the major reason for antibiotic resistance to build up.