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NCERT Solution for Class 9 Science Chapter 13: Why Do We Fall Ill

Why Do We Fall Ill
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In this chapter, you will understand the significance of health, acute and chronic diseases, causes of diseases, etc. After reading this chapter, you will understand the value of hygiene for our good health.

NCERT Solution Class 9 Science of Chapter 13 includes all Intext exercises and NCERT exercises for you. The NCERT exercise includes solutions to all 6 questions given in your NCERT Textbook. These questions will test your understanding ability and memorizing skills.

Ncert solutions

NCERT Solution for Class 9 Science Chapter 13: Why Do We Fall Ill Ex 13.1

Exercise 13.1.3

State any two conditions essential for good health

Two conditions essential for good health are
(i) Availability of sufficient and nutritious food.
(ii) Better sanitation or clean surroundings.

State any two conditions essential for being free of disease.

The conditions essential for being free of disease are
(i) Taking good food (balanced diet)
(ii) Maintaining personal and public hygiene,

Are the conditions essential for maintaining good health and being free of
disease are same or different?

Answers to both these questions are different, but interconnected. if the conditions that are essential for good health are maintained . then the chances of getting a disease will be minimized automatically.

Exercise 13.2.5

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?

These reasons due to which we think we are sick are
1) Cough, cold and high fever
2) Having diarrhea (loose motions)
3) Having a wound with pus
These symptoms indicate disease but do not tell what the disease is. So, it is advisable to go to the doctor to diagnose the disease. The doctor will get laboratory tests done (if required) for the com formation of particular disease. If the infection remain untreated, it will cause further damage to the body.

In which of the following case 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 acne.
c) If you get acne.

Lice and acne will not cause long lasting effects on out body. But in case of jaundice, there will besevere long lasting effects.
For example,
(i) High temperature, headache and joint pain
(ii) Feeling of nausea and vomiting
(iii) irritating rashes
The patient will suffer from poor health and will only recover by taking complete bed rest for some time.

Exercise 13.3.5

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

Infection diseases show a lack of success of the immune system of the body. For the functioning of immune system properly, sufficient nourishment and easily dies table food is necessary for a sick person.

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

Infectious diseases are spread by the following means
1) Through air: An infected person, when sneezes or coughs releases out droplets containing germs. Which infects, another healthy person by entering into their body through air. Examples of such diseases are common cold, pneumonia and tuberculosis.
2) Through water: If the water source is polluted by the excreta of infectious individuals having gut diseases and this water is used by other people they will be infected by diseases eg. Cholera, amoebiasis, hepatitis, which gets spread though water.
3) Through sexual contact: Some diseases like AIDS and syphilis, etc., are transmitted by sexual contact.
4) Through vectors: There are some organisms which act as intermediates or vectors for a particular disease. These vectors carry diseases from infected person to the healthy person, e.g., mosquito spread malaria in humans, by sucking their blood.

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

To prevent the incidence of infectious diseases in school, following precautions can be taken
1) Avoid contact with student suffering from airborne diseases like common cold, cough, eye flu, etc.
2) By checking the availability of clean drinking water in school.
3) By maintaining cleanliness, to protect against files and mosquitoes.
4) Starting immunization programmed in schools.

What is immunization?

Development of immunity or resistance against a pathogen through vaccination is called immunization. The process of immunization is based on the principle of developing a memory for a particular infection, by introducing the microbes in the body. This does not actually cause the disease but prevent any subsequent exposure to the infecting microbes from turning into actual diseases.

What are the immunization programmers available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?

(Suggested Answer)
The following immunization programmed is available at the nearest health center in our locality.
1) Immunization for infants DPT, BCG, polio, measles and MMR.
2) Immunization for children Typhoid TT, DT, smallpox and TAB.
3) Immunization for pregnant women: TT and hepatitis -B the diseases like typhoid, polio, measles, tetanus, etc., are the major health problems in our locality. To prevent these diseases, the government has initiated expanded immunization programmed all over the country.

Exercise Chapter 13

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 illnesses.
b) Think of one change you would wish for you. Surroundings in order to avoid any of /most of the illnesses.

I fell ill twice in the last one year. The diseases, from which i suffered were diarrhea and dengue fever.
a) The changes i will do in my habits after suffering from these diseases are
1) I will always drink clean, pure water and wash hands before eating anything.
2) I will live in clean surroundings where disease speeding vectors (e.g. mosquitoes) could not multiply.
b) The intake of impure water is the main cause of many infectious diseases. Thus, to remain protect pure drinking water should be always available in the surrounding.

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.

A doctor/nurse/health-worker takes following precautions to avoid getting sick
1) Wear masks while diagnosing mouth or chest infections.
2) Clean their hands and wear gloves even while doing mi nor surgeries.
3) Get immunisaiton done against all the infectious diseases.
4) Take balanced diet (especially rich in proteins) to strengthen their immune system.
4) Dispose of blood samples, urine or stool , sputum, etc., carefully.
5) Keep work place sterilised by using phenyl.

Conduct a survey in your neighborhood to find out what the three most
common diseases are. Suggest three steps that could be taken by your local authority to bring down the incidence of these diseases.

Solution:  Refer pdf.

A baby is not able to tell her / his caretakers that he/ she is sick. What would
help us to find out?
a) That the baby is sick?
b) What is the sickness?


a) Symptoms which help in finding that the baby is sick are
(i) Continuous crying (ii) Drooping of eyes (iii) Redness of eyes (iv) High temperature of body
b) Signs which help to indicate the sickness in baby are
(i) Loose motions and stomach pain indicate diarrhea.
(ii) High fever, headache, muscular pain, feeling of shivering and cold indicate malaria.
(iii) Redness and persistent rubbing of eyes indicate eye flu.
(iv) Pale skin, yellow urine and yellowing of eyes indicate jaundice.
(iv) Doctors suggest for laboratory tests, it there is fever with no other symptoms, to find out the kind of sickness.

Under which of the following condition 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 condition in which a person is most likely to fall sick when she is on a four-day fasting as soon as she has recovered from malaria and is taking care of someone suffering from chicken-pox. Because she has not completely recovered from malaria and she is fasting when her immune system is still weak. 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.

Under which of the following conditions are you most likely to fall sick?
a) When you are taking examination?
b) When you have travelled by bus and train for two days?
c) When your friend is suffering from measles. Why

In condition (c), chances of falling sick are maxi« mum, Measles is an infectious viral disease of young children. Which spreads through nasal or throat discharge? Being in contact with a friend suffering from measles can cause the infection to be transmitted to you.

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