NCERT solution for class 9 science why do we fall ill ( Chapter 13)

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Solution for Exercise Questions

1. How many times did you fall ill in the last one 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.


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Answer :

I fell ill maybe 50 times in the last year. I suffered from cold, cough and fever.

(a) The changes made by me in my habits after suffering from these diseases are:

(i) I will always drink purified and clean water and wash my hands before eating any food item.

(ii) I will live in a clean environment where disease spreading vectors will not multiply.

Example of multiplying vectors are mosquitoes.

(b) One change I would wish for in our surroundings in order to have a healthy society is by making pure drinking water available for the people. Consuming impure water is the root cause of many infectious diseases.

2. 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.

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Answer :

Some important precautions that need to be taken by the doctor/nurse/health-worker while treating people who are sicker than others in the community are :

(a) When in contact with a diseased person not to forget to wear a mask.

(b) Drinking purified water.

(c) Not neglecting cleanliness and personal hygiene.

(d) Keeping themselves covered appropriately when moving in an infected region

(e) Eating nutritious food and maintaining a healthy diet.

3. 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.

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Answer :

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

Cold and cough, malaria, fever.

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.

4. 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?

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Answer :

(a). It can be found out by observing the behavioral changes of the child such as:

Improper food intake

Constant crying

Mood changes frequently

(b). The sickness can be determined with the help of symptoms or indications shown by the child. The symptoms could be loose motion, vomiting, paleness in body, and fever.

5. 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 chicken-pox.

(c) when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox. Why?


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Answer :

In condition (c) she is more likely to fall sick as she has just recovered from malaria but her immune system is still weak and she is not taking proper diet. At this stage her body will not be able to fight against infection and if she is taking care of someone else suffering from chicken pox even she can get infected with chickenpox virus and will fall sick again.

6. 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. Why?

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Answer :

A person can most likely fall sick when his/her friend is suffering from measles. It can easily be transferred through air and respiration. It is always better to stay away from your friend who is affected with measles else even you will get infected with the disease.

Solution for Intext Question

Q. State any two conditions essential for good health.

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Answer :

Two conditions essential for good health are:

  • Good economic condition.
  • Good social environment.
  • Q. State any two conditions essential for being free of disease.

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    Answer :

    Two conditions essential for being free of disease are:

  • Living in a healthy and hygienic environment.
  • Get vaccination against infectious disease whenever required.
  • Q. Are the answers to the above questions necessarily the same or different? Why?

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    Answer :

    No, the answer to the above question are not same as their is a difference between a person healthy person and a disease free person. As a person can be disease free but not healthy if he is not mentally, socially and economically upright.

    Q. 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?

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    Answer :

    Three reasons why we would think that we are sick and ought to see a doctor are:

    (a). Headache

    (b). Fever

    (c). Cold and cough

    We usually not visit doctor if any one of these are present as we try to cure them with home remedies. But if these symptoms are for quite long, it is better if we go and visit a doctor as he will be able to know the reason why this is happening.

    Q. 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?

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    Answer :

    Three reasons why we would think that we are sick and ought to see a doctor are:

    (a). Headache

    (b). Fever

    (c). Cold and cough

    We usually not visit doctor if any one of these are present as we try to cure them with home remedies. But if these symptoms are for quite long, it is better if we go and visit a doctor as he will be able to know the reason why this is happening.

    Q. In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?

  • if you get jaundice
  • ]if you get lice
  • if you get acne. Why?

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  • Answer :

    Jaundice causes a long term effect on our health. This chronic disease lasts for a long period of time. Jaundice develops slowly and does not spread rapidly.

    Q . Why are we normally advised to take bland and nourishing food when we are sick?

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    Answer :

    When we fall sick, normal body functioning gets disturbed. As a result, improper digestion ability, we lose appetite and absorption of food is slow. Therefore, we are advised to take bland and nourishing food during sickness as it is easily digested and contains adequate nutrients, vitamins, and minerals to produce energy.

    Q. What are the different means by which infectious diseases are spread?

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    Answer :

    Different means by which infectious diseases are spread are:

    (i) Through air: When an infected person sneezes or coughs small droplets are thrown out.

    (ii) Through water: This occurs if the excreta from someone suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby.

    (iii) Through physical contact: Casual physical contacts include handshakes or hugs or sports, like wrestling, or by any of the other ways in which we touch each other socially.

    (iv) Through vectors: These animals carry the infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are called vectors.

    Q. What precautions can you take in your school to reduce the incidence of infectious diseases?

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    Answer :

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

    (a) Trying to stay away from students who are infected.

    (b) Covering mouth and nose while coughing and sneezing.

    (c) Keeping the school environment clean so that there are no multiplication vectors.

    (d) Consuming safe aqua guard water.

    Q. What is immunisation?

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    Answer :

    The method to boost our immune system with the help of vaccines that help the body to fight against infectious diseases is called immunisation.

    Q. What are the immunisation programs available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?

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    Answer :

    The immunisation programs available at the nearest health centres are Measles, Mumps, and Rubella (MMR), polio vaccine, jaundice, diphtheria, and Tetanus (DPT), typhoid, hepatitis A. Typhoid and jaundice create major health problems.