Chapter 13 Why do we fall ill ?

By | July 3, 2018

Class 9 | Science | Chapter 13| Why do we fall ill | NCERT Solutions

Page 178

1. State any two conditions essential for good health.    

is a state of complete physical, mental and social well being.

The two conditions essential for good health are

1) We need food for health and food will have to earn by doing work.For this, opportunity  to do work has to be available.Good economic condition and jobs are therefore needed for individual health. 

2) We need to be happy in order to be truly healthy.If we mistreat each other and are afraid of each other, we cannot be healthy or happy.Social equality and harmony are important for individual health.

2. State any two conditions essential for being free of disease.

The two conditions essential for being free of disease are :

1) Personal and domestic hygiene

2) Intake of proper balanced diet

3. Are the answers to the above questions necessarily the same or different? Why?

No.This is because a disease free state is not the same as being healthy.Health is a state of complete physical, mental and social well being whereas disease is about an individual sickness.

Page 180

1. 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?

Common symptoms which indicate sickness are

1) Headache

2) Cough


It is necessary to visit a doctor , if any of these symptoms were present because these symptoms basically indicate that there might be a disease but we cannot predict the exact reason and cause of disease.On delaying and carelessness it may cause serious problems.

2. 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?

Jaundice is a disease that can cause long term effects on our health.It is a chronic disease that lasts for a long period of time.It does not spread rapidly, but develops slowly over a long period of time.

Page  186

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

When we are sick the normal body function get disturbed.It is advised to take bland and nourishing food when we are sick because it provides sufficient nutrients, is easy to digest , gives energy quickly which are needed  for proper functioning of immune system.

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

1)Air-borne diseases
:Microbial agents can move from an affected person to someone else through air.It occurs through the little droplets thrown out by an infected person who sneezes or coughs.Someone standing close by can breathe in these droplets, and microbes get chance to start a new infection.

For Ex:Common cold, pneumonia, tuberculosis

2)Water-borne diseases:They can be spread through water.If the excreta from someone suffering from an infectious gut disease such as cholera or amoebiasis gets mixed with drinking water used by people living nearby.

3)Sexually Transmitted diseases(Syphilis,AIDS):These diseases are transmitted by sexual contact from one partner to other.However these diseases are not transmitted by causal physical contact.
AIDS virus can also spread through blood to blood contact with infected people or infected mother to her baby during pregnancy or breast feeding.

4)Through vectors:Vectors are carrier of a disease or infection.

Many animals which live with us may carry disease.These animals carry infecting agents from a sick person to another host.
Mosquitoes are vector of a disease called malaria.
In many species of mosquitoes, the female need highly nutritious food in the form of blood in order to be able to lay mature eggs.Hence they feed on warm blooded animals.In this way they can transfer diseases from person to person.

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

Precautions to reduce the incidence of infectious disease are:

1) Stay away from infected person

2) Cover your mouth and nose while coughing or sneezing.

3) Drink safe and clean water.

4) Use clean toilets

5) Do not allow water to stagnate in or around school.

6) Avoid eating food exposed to flies.

4. What is immunisation?

Immunisation is defined as a process by which an individual is made immune to an infectious disease by administration of an external agent or vaccine.

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?

The various immunisation programmes available in the nearest health centre in our locality are:

1) BCG vaccine against Tubercluosis

2) Polio drops

3) Chicken Pox vaccine

4) Hepatitis vaccine

5) DPT vaccine

Chicken pox and hepatitis are the major health problems in our area.

Exercise Page 187, 188

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.

The precautions taken by doctor/ nurse/ health -workers are:

1) They wear mask when they come in contact with infected person

2) They drink safe water.

3) They eat balanced diet.

4) They take care of environmental and personal hygiene

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.

Tuberculosis, typhoid and jaundice.

In order to prevent these diseases there should be proper disposal of waste, supply of safe drinking water and proper care about the environment hygiene.

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?

The baby is sick can be determined by his/her behavioural change such as constant crying of baby, improper intake of food, loose motion, mood change etc.

The sickness is determined by the symptoms seen in baby.These symptoms may include high fever, vomiting, loose motion ,loss of weight, paleness of body etc.

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?

A person is most likely to fall sick when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox.This is because she is 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 she is taking care of person suffering from chicken pox, then she has more chances of getting infected.

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?

You are most likely to fall sick when your friend is suffering from measles. This is because measles is highly contagious and easily spread through respiration.

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