the bacteria streptococcus pneumoniae has a virulent s strain and a nonvirulent r strain. the s strain is lethal to mice. the s strain contains a chemical factor that can transform the r strain to be virulent. the diagram shows a series of experiments conducted by injecting combinations of these strains into mice to identify the transforming factor.

Smoking damages the respiratory system by inhalation of a foreign substance, that is absorbed and residue is left behind on our lungs sponge like substance. the gas that is inhaled also increase your blood pressure and dilates your blood vessels. also the process of inhaling and exhaling the smoke it causes irritation to the throat and mouth. smoking can cause lung cancer and other respiratory and circulatory diseases.