I would say that the sentence which provides supporting evidence for that statement is the second one - <em>Each gene has a specific code of base cells responsible for telling the body how it will look, how it will digest food or battle infection, and sometimes even how it will act. </em>It is the only sentence which talks both about the evolution and mentions diseases.<em> </em>
As a former slave, Frederick Douglass felt that education is the only way to break the chains of slavery. An educated man is free from ignorance and cannot be enslaved, so slaves should strive to get educated by any means possible.