Ans. Microorganisms can cause diseases by entering our body and multiplying rapidly. They can enter through various means such as inhalation, ingestion, or through cuts and wounds. Once inside the body, they can release toxins or damage our body tissues, leading to illness. Examples of diseases caused by microorganisms include tuberculosis, pneumonia, influenza, and food poisoning. Proper hygiene practices and vaccination can help prevent the spread of these diseases.