NCERT Solutions For Class 9th Science Why Do We Fall ill ~ Free PDF Download


CBSE Class 9 Science Chapter Why Do We Fall ill NCERT Solutions PDF Download :- Welcome to today we are going to tell you CBSE Class 9 Science Chapter Why Do We Fall ill NCERT Solutions. These questions can help you a lot in the upcoming papers, so read all these questions carefully.

Why Do We Fall Ill ncert solutions

NCERT Solutions for Biology Chapter 13 – Why Do We Fall Ill

1. State Any Two Conditions Essential for Good Health. 

Ans: Two conditions essential for good health are: 

  • Availability of better health facilities to deal with problems. 
  • Basic necessary conditions to stop diseases must be present.  

2. State Any Two Conditions Essential for Being Free of Disease. 

Ans :- Two conditions essential for being free of disease are:

  • 1. Personal and domestic hygiene.
  • 2. Clean environment and surroundings.

3. List Any Three Reasons Why You Would Think That You Are Sick and Ought to See a Doctor. If Only One of These Symptoms Were Present, Would You Still Go to the Doctor? Why or Why Not? 

Ans: The 3 reasons why one would think that he is sick are—(1) headache, (2) cold and cough, (3) loose-motions. This indicates that there may be a disease but does not indicate what the disease is. So one would still visit the doctor for the treatment and to know the cause of above symptom. Even in case of single symptom one needs to go to the doctor to get proper treatment.

4. In Which of the Following Cases Do You Think the Long-Term Effects on Your Health are Likely to Be Most Unpleasant? 

  • (a) If you get jaundice, 
  • (b) If you get lice, 
  • (c) If you get acne. 


Ans: Lice and acne will not cause any long-term effects on the human body. The long-term effects on our health are likely to be most unpleasant if we get jaundice because the symptoms severely affect our internal organs and persist for a long time.

5. Why are We Normally Advised to Take Bland and Nourishing Food When We are Sick? 

Ans: Infectious disease show a lack of success of the immune system of the body. For the functioning of immune system properly, sufficient nourishment and easily digestible food is necessary for a sick person.

6. What are the Different Means by Which Infectious Diseases are Spread?

Ans: The different means by which infectious diseases are spread are as follows:

Diseases can be spread through various means such as air, water, sexual contact, blood and vector. 

  • Through Air – This occurs through the little droplets thrown out by an infected person during sneezing or coughing. For example, tuberculosis, pneumonia, etc. spread through the air. 
  • Through Water – This occurs if the excreta of an infected person who is suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby. 
  • Through Physical Contact – Sexual act is one of the closest physical contact two people can have with each other. 
  • Blood Transfusion – Certain diseases such as AIDS can spread via the blood to blood contact during a blood transfusion or pregnancy. 
  • Through Vectors – Diseases can spread through vectors. For example, mosquitoes spread malaria. 

7. What Precautions Can You Take in Your School to Reduce the Incidence of Infectious Diseases? 

Ans :- Some of the precautions that we can take in our school to reduce the incidence of infectious diseases are :

  • 1. Drinking clean and hygienic water.
  • 2. Preventing the accumulation of water in surroundings.
  • 3. Keeping the toilet neat and clean.
  • 4. Avoiding consumption of uncovered food and other eatables.
  • 5. Taking bath daily
  • 6. Have a balanced diet.
  • 7. Provide a clean environment which prevents the breeding of mosquitoes. This prevents the spread of vector-borne diseases.

8. What is Immunization? 

Ans: When the body attains immunity against any disease, due to vaccination. This process is called immunisation.

9. What are the Immunization Programmes Available at the Nearest Health Centre in Your Locality?  Which of These Diseases Are the Major Health Problems in Your Area?


  • DPT vaccine: it is for diphtheria, pertussis and tetanus in infants.
  • Pulse polio vaccine: it is to prevent polio.
  • BCG vaccine: bacillus calmette Guerin vaccine for tuberculosis.
  • Hepatitis vaccine
  • TAB vaccine for typhoid.
  • tuberculosis and diarrhea are the major health problems in our area.

Questions From NCERT Textbook for Class 9 Science

10. How Many Times Did You Fall Ill in the Last Year? What Were the Illnesses? 

  • (a) Think of one change you could make in your habits in order to avoid any of /most of the above illnesses. 
  • (b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses. 

Ans: It depends on the immunity system of the individual. Few might fall ill several times in a year whereas others do not fall ill at all.

  • Eating fresh, healthy food and drinking safe, pure or boiled water.
  • There should be no accumulation of garbage.

11. A Doctor/Nurse/Health Worker is Exposed to More Sick People Than Others in the Community. Find Out How She/He Avoids Getting Sick Herself/Himself. 

Ans: A doctor/nurse/health worker when exposed to sick people they keep their nose and mouth covered, take care of hygiene, wash hands with soap before drinking water or eating food. They use mask, gloves, etc to avoid the direct contact with the person suffering from infectious diseases.

12. Conduct a Survey in Your Neighbourhood to Find Out What the Three Most Common Diseases Are. Suggest Three Steps That Could Be Taken by Your Local Authorities to Bring Down the Incidence of These Diseases. 

Ans: The following three are the most common diseases in any neighbourhood:

Cold and cough, loose motions, and malaria.

Some of the preventive measures that can be taken are:

  • (a). By drinking fresh, uncontaminated, and clean water.
  • (b). By maintaining hygienic sanitary conditions.
  • (c). By educating people about various preventive measures with the help of posters, and pamphlets

13. A Baby is Not Able to Tell Her/His Caretakers That She/He is Sick. What Would Help Us to Find Out 

  • (a) That the baby is sick? 
  • (b) What is the sickness? 

Ans: Following symptoms will help a caretaker to know regarding the illness/sickness of a baby:

  • (a) By the behavioural changes of the baby sickness can be determined. 
  • (b) Sickness can be symptoms or indications which include vomiting, fever, loose motion,  paleness in the body, etc. 

14. Under Which of the Following Conditions is a Person Most Likely to Fall Sick? 

  • (a) When she is recovering from malaria. 
  • (b) When she has recovered from malaria and is taking care of someone suffering from chickenpox. 
  • (c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chickenpox. Why? 

Ans: Under the condition ‘C’ a person is more likely to fall sick because she is already fasting during recovery, and her immune system is so weak that it is not able to protect its own body from any foreign infection. If that person is taking care of someone suffering from chickenpox, then she has more chances of getting infected from the chickenpox virus and will get sick again with this disease. 

15. Under Which of the Following Conditions are You Most Likely to Fall Sick?

  • (a) When you are taking examinations. 
  • (b) When you have travelled by bus and train for two days. 
  • (c) When your friend is suffering from measles. 


Ans: We are most likely to fall sick when a friend is suffering from measles since measles is a very infectious/ communicable disease that can spread easily from one person to the other easily.

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