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Class nine Science Chapter 13 NCERT

Chapter 13: Why do we fall ill?

NCERT TEXTBOOK Questions-Answers

TEXTBOOK EXERCISE

Q. 1. 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 in your surroundings in order to avoid any

of / most of the above illnesses.

Ans. The illness was a common cold, 2-3 times, it occurred in a year.

(a) one change I would make in my habits in order to avoid the above illness is, take

a proper diet rich in vitamin ‘C’, not to make too cold food.

(b) The surroundings should be neat and clean.

Q. 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.

Ans. (i) They use a mask while coming close to the infected persons to protect themselves from air-borne diseases.

(ii) They get them vaccinated against diseases like hepatitis, typhoid, rabies, tuberculosis etc.

(iii) Proper washing of exposed parts after coming in contact with infected persons.

Q. 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.

Ans. The survey revealed that the three most common diseases in the neighbourhood are cholera, typhoid and malaria. Suggested measures to be taken by the authorities :

(i) Spraying of insecticides like DDT, to kill mosquito vectors of malaria.

(ii) Providing safe and germ-free drinking water to avoid spreading of cholera.

(iii) People should be made aware of preventive measures through health education programmes.

Q. 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?

Ans. (a) Sickness can be known by certain symptoms, e.g., loose motions, rash on the body, sneezing, chest pain, etc.

(b) Kind of sickness can be known by certain organ-specific and tissue-specific symptoms, e.g. yellowness of skin and eyes indicate jaundice and hepatitis.

Q. 5. Under which of the following conditions is a person most likely to fall sick?

(a) When he/she is recovering from malaria.

(b) When he/she has recovered from malaria and is taking care of someone suffering from chicken-pox.

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

Ans. If a person is most likely to fall sick in (c) condition because malaria attack has caused large scale destruction of his blood cells so he is weak and anaemic. Then he is on a four day fast so is not getting proper and sufficient food which further decreases the functioning of the immune system and lastly, chicken-pox is a communicable and contagious disease.

Q. 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?

Ans. I will most likely to fall sick when my friend is suffering from measles and I come in contact with him because measles is a contagious disease and also spreads by droplet infection.

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