CBSE – 9th Standard Science

Class 9 Question Bank Chapter 13 – Why do we fall ill


Q1. What is Health?

Ans. Health is a state of being well enough to function well physically, mentally and socially.

Q2. Health of organisms depends on what factor?

Ans. The health of all organisms will depend on their surroundings or their environment.

Q3. What plays an important factor in our individual health?

Ans. Our social environment is an important factor in our individual health.

Q4. What is Disease?

Ans. The word is actually self-explanatory ‘disease’ – disturbed ease. Disease, in other words, literally means being uncomfortable.

Q5. What is the most obvious factor of disease?

Ans. One of the most obvious factors that determine how we perceive the disease is its duration.

Q6. What are acute diseases?

Ans. Some diseases last for only very short periods of time, and these are called acute diseases.

Q7. What are chronic diseases?

Ans. Other ailments can last for a long time, even as much as a lifetime, and are called chronic diseases.

Q8. What is Infectious disease?

Ans. Diseases where microbes are the immediate causes are called infectious diseases. This is because the microbes can spread in the community, and the diseases they cause will spread with them.

Q9. What are non infectious diseases?

Ans. On the other hand, there are also diseases that are not caused by infectious agents. Their causes vary, but they are not external causes like microbes that can spread in the community.

Q10. Give examples of diseases spread by viruses?

Ans. Common examples of diseases caused by viruses are the common cold, influenza, dengue fever and AIDS.

Q11. Give examples of diseases spread by bacteria?

Ans. Diseases like typhoid fever, cholera, tuberculosis and anthrax are caused by bacteria.

Q12. Why skin infections take place?

Ans. Many common skin infections are caused by different kinds of fungi.

Q13. What protozoan microbes cause?

Ans. Protozoan microbes cause many familiar diseases, such as malaria and kalaazar.

Q14. What are communicable diseases?

Ans. Many microbial agents can commonly move from an affected person to someone else in a variety of ways. In other words, they can be ‘communicated’, and so are also called communicable diseases.

Q15. What are vectors?

Ans. These animals carry the infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are called vectors.

Q16. What are the most common vectors?

Ans. The commonest vectors we all know are mosquitoes.

Q17. On which factors signs and symptoms of disease depends?

Ans. The signs and symptoms of a disease will thus depend on the tissue or organ which the microbe targets.

Q18. What is inflammation?

Ans. An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes. This recruitment process is called inflammation.

Q19. Why anti viral medicines are harder to make than anti bacterial medicines?

Ans. One reason why making anti-viral medicines is harder than making antibacterial medicines is that viruses have few biochemical mechanisms of their own. They enter our cells and use our machinery for their life processes.

Q20. On what factors immune system depends?

Ans. The functioning of the immune system, like any other system in our body, will not be good if proper and sufficient nourishment and food is not available.

Try these:-

  1. Why are we normally advised to take bland and nourishing food when we are sick?
  2. What are the different means by which infectious diseases are spread?
  3. What precautions can you take in your school to reduce the incidence of infectious diseases?
  4. What is immunisation?
  5. What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?