Entomology is the scientific study of insects. It involves the examination of the biology, behavior, ecology, taxonomy, physiology, and evolution of insects. Entomologists, the scientists who specialize in this field, study a vast and diverse group of organisms, which make up the largest class of animals on Earth. The knowledge gained through entomology has wide-ranging applications, from understanding ecosystems and biodiversity to pest management and forensic entomology.

All of these diseases are caused by bacteria i.e. Pneumonia, Cholera, Tuberculosis. Cancer is caused by uncontrolled cell division. Pneumonia is caused by a bacterium Streptococcus pneumoniae. Cholera is caused by a bacterium Vibrio cholerae.