Important Questions Class 9th Science Why Do We Fall ill ~ Free PDF Download


CBSE Class 9 Science Chapter Why Do We Fall ill Important Questions/Previous Year Questions | CBSE Class 9 Why Do We Fall ill MCQ, 2 Marks Question & 3 Marks Questions/Extra Questions PDF Download :- Welcome to today we are going to tell you CBSE Class 9 Science Chapter Why Do We Fall ill Extra Questions/Important Questions. These questions can help you a lot in the upcoming papers, so read all these questions carefully.

Why Do We Fall ill MCQ ~ 1 Mark Questions

1. Which one of the following is not important for individual health?

  • (a) Living in clean space
  • (b) Good economic condition
  • (c) Social equality and harmony
  • (d) Living in a large and well-furnished house.

Ans. (d) Living in a large and well-furnished house

2. ‘Penicillin’, a lifesaving antibiotic, was discovered by

  • (a) Alexander Fleming
  • (b) Edward Jenner
  • (c) H.G. Khorana
  • (d) William Harvey.

Ans. (a) Alexander Fleming

3. Making anti-viral drugs is more difficult than making anti-bacterial medicines because-

  • (a) Viruses make use of host machinery.
  • (b) Viruses are on the border line of living and non-living
  • (c)Viruses have very few biochemical mechanisms of their own
  • (d) Viruses have a protein coat.

Ans. (c)Viruses have very few biochemical mechanisms of their own

4. Which one of the following deficiency disease?

  • (a) Diabetes
  • (b) Malaria
  • (c) Goitre
  • (d) Tetnus

Ans. (c) Goitre

5. The chemical that kill or stop the growing of certain kinds of microbes are called-

  • (a) vaccines
  • (b) microbes
  • (c) antibiotics
  • (d) fungi

Ans. (c) antibiotics

6. Choose the wrong statement –

  • (a) High blood pressure is caused by excessive weight and lack of exercise.
  • (b) Cancers can be caused by genetic abnormalities.
  • (c) Peptic ulcers are caused by eating acidic food.
  • (d) Acne is not caused by staphylococci.

Ans. (d) Acne is not caused by staphylococci.

7. Rabies occurs through the bite of.

  • (a) female Anopheles Mosquito
  • (b) Female culex mosquito
  • (c) Rabid dog
  • (d) housefly.

Ans. (c) Rabid dog

8. AIDS is caused by –

  • (a) Bacteria
  • (b) Virus
  • (c) Protozoa
  • (d) Fungi

Ans. (b) Virus

9. Identify a protozoan disease –

  • (a) Ringworm
  • (b) Measles
  • (c) Diphtheria
  • (d) Amoebiasis

Ans. (d) Amoebiasis

10. If you live in a overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases.

  • (a) Cancer
  • (b) AIDS
  • (c) Air borne diseases
  • (d) Cholera.

Ans. (c) Air borne diseases

11. The symptom of goiter is

  • (a) Swelling of eye
  • (b) Swelling of the thyroid gland
  • (c) Swelling of the liver
  • (d) Swelling of the limbs.

Ans. (b) Swelling of the thyroid gland

12. Which one of the following does not help in the prevention of AIDS?

  • (a) Use of disposable syringes.
  • (b) Safe sex practiced between single partners.
  • (c) Proper screening of blood before transfusion
  • (d) Using same syringe again and again

Ans. (d) Using same syringe again and again

13. You are aware of Polio Eradication Programme in your city. Children are vaccinated because –

  • (a) vaccination kills polio causing micro-organisms
  • (b) Prevents the entry of polio causing micro-organisms
  • (c) It creates immunity in the body.
  • (d) all the above.

Ans. (c) It creates immunity in the body.

14. ‘BCG’ vaccine is given to infants for protection against –

  • (a) Diarrhoea
  • (b) cholera
  • (c) Pneumonia
  • (d) Tuberculosis

Ans. (c) Pneumonia

15. Which one is not sexually transmitted disease

  • (a) AIDS
  • (b) Gonorrhoea
  • (c) syphilis
  • (d) Diabetes.

Ans. (d) Diabetes.

16. Which one of the following causes kala-azar?

  • (a) Ascaris
  • (b) Trypanosome
  • (c) Leishmania
  • (d) Bacteria

Ans. (c) Leishmania

Why Do We Fall ill Important Questions ~ 2 Mark Questions

1. State any two conditions essential for good health.

Ans. Two conditions essential for good health are:

  • (i) hygienic surroundings
  • (ii) good economic and social status

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

Ans. Two conditions essential for being free of disease:

  • (i) healthy habits and surroundings
  • (ii)mental stability and financial status

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

Ans. Answers though not identical are similar because for being disease free one needs to be physically and mentally healthy.

4. 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 or der 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. I fall ill only once last year. I had suffered from typhoid.

  • (a) I will avoid street food specially those which are cooked at unhygienic places and kept uncovered.
  • (b) I shall keep my surroundings cleaner than earlier.

5. 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 is exposed to more sick people than others in the community still they avoid getting sick themselves because they take care of the preventive measures like personal and community hygiene/cleanliness and immunisation to prevent infectious diseases.

6. 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) If the baby is crying and remains restless no matter whatever is done to ease him/her out then he/she is sick.

(b) We must observe symptoms and severity of the symptoms to diagnose the sickness.

7. 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?

Ans. 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 because during her fast she was on a limited diet and didn’t get sufficient nourishment hence her health condition is poor such that she is very likely to fall sick.

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

9. How are acute diseases different from chronic diseases?

Ans. Acute disease – Diseases which last for short periods of time and are severe are called acute diseases.

Chronic disease – Diseases which are long lasting are called chronic diseases.

10. What is the full form of AIDS? Name the causal organism.

Ans. AIDS – Acquired Immuno deficiency syndrome It is caused by HIV – Human Immuno deficiency virus.

11. State two conditions essential for keeping good health.

Ans. Conditions for keeping good health are

  • (a) Public and personal hygiene
  • (b) Regular exercise, sleep and relaxation.
  • (c) Proper habits.
  • (d) Nutrition

12. Define

  • (a) health
  • (b) disease.

Ans. (a) Health – It is defined as a state of complete physical, mental and social well being and not merely the absence of disease or infirmity.

(b) Disease – A disease in the malfunctioning of body organs due to one reason or the other.

13. What are non-communicable diseases? Give examples.

Ans. Non-communicable diseases are those which cannot be spread from person to person. For example – Diabetes, cancer.

14. Define carriers. Give two examples.

Ans. Carriers are the organisms which harbor disease-causing germs without showing away sign of disease themselves, but have the ability to infect other healthy individuals.

For Example – Housefly, female insect Anopheles.

15. Why do children need vaccination?

Ans. The children are more susceptible to disease, hence are given vaccines to develop immunity against some diseases.

16. How can we prevent influenza?

Ans. Influenza is an air borne disease, so it is prevented by keeping away from the patients.

17. State giving reasons whether the following statements are correct or not.

  • (a) Health is only the absence of any physical disease.
  • (b) Children need not be immunized.

Ans. A) This statement is incorrect because health is a state of complete physical, mental and social well being, not merely absence of disease.

b) This statement is incorrect because children need to be immunized because of poorly developed immune system they are more susceptible to diseases.

18. What is peptic ulcer?

Ans. Peptic ulcer is a disease in which patient is suffering from acidity related pain and bleeding in the stomach and duodenum, due to stressful life style.

19. What are the different types of diseases? Explain them.

Ans. Diseases are broadly grouped into two types –

  • a) Communicable or infectious disease – Those diseases which are passed on from one person to another in various ways through air, water, food, physical contact and insects.
  • b) Non-communicable diseases – Those diseases which cannot be spread from person to Peron. Forex – arthritis, marasmus etc.

20. Which bacterium causes peptic ulcers? Who discovered the above pathogen?

Ans. Peptic ulcer is caused by bacterium Helicobacter pylori, it was discovered by Robin warren and Barry Marshall.

21. Name the target organs for the following disease-

  • (a) Hepatitis targets ______________
  • (b) Fits or unconsciousness targets __________________
  • (C) Pneumonia targets _________________
  • (d) Fungal disease targets ______________

Ans. a) liver

b) Brain

c) lungs

d) skin

22. How are diseases diagnosed by physician?

Ans. The malfunctioning of organs produces external symptoms of diseases. Symptoms indicate that there is something ‘wrong’ within the body. On the basis of symptoms doctor diagnosed the diseases.

23. Who discovered ‘vaccine’ for the first time? Name two diseases which can be prevented by using vaccine.

Ans. Vaccine was discovered by a surgeon, Edward Jenner. Two diseases which can be prevented by using vaccines are polio and tetanus.

24. Name the approaches generally adopted to treat infectious diseases.

Ans :-

  • By reducing its effect using medications that may reduce its symptoms.
  • By killing its cause using antibiotics.

25. What is the purpose of vaccination ?

Answer. The purpose of vaccination is to induce the production of specific antibodies to confer immunity against subsequent infection.

26. Many vaccines form the public health programme of childhood immunisation for preventing infectious disease. Name any two such diseases.

(i) Vaccine against measles.
(ii) BCG vaccine against T.B.

27. Name two diseases caused by Protozoans. What are their causal organisms ?

Ans :-
(i) Sleeping sickness caused by Trypanosoma, Malaria by Plasmodium.
(ii) Kala-azar caused by Leishmania.

28. What is an antibiotic ? Give two examples.

Answer. Antibiotic is a chemical substance that kills bacteria, secreted by microorganisms which can kill the pathogens. Examples, Penicillin and Streptomycin.

29. What do signs and symptoms indicate if a person is suffering from any disease ?
Ans :-
Signs and symptoms indicate presence of a particular disease. Because when there is a disease, either the functioning or the appearance of one or more systems of the body will change for the worse.

30.  Give four modes of transmission of AIDS.

  • Blood to blood contact (transfusion).
  • From an infected mother to her unborn baby during pregnancy, labour or delivery.
  • Through breast feeding.

31. Why are we normally advised, to take bland and nourishing food when we are sick ?
Ans :-
When a person is sick, then his normal body functions get disturbed. In such a situation, such food is required which is easy to digest and contains adequate nutrients for the speedy recovery. Thus, bland and nourishing food is required during sickness.

Why Do We Fall ill Important Questions ~ 3 Mark Questions

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

Ans. We are normally advised to take bland and nourishing food when we are sick because we are weak during illness and need complete nourishment for faster recovery.

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

Ans. Infectious diseases can spread by following means:

  • a) through contaminated food and water
  • b) through air
  • c) through vectors or carriers (housefly, mosquito etc)
  • d) through direct skin contact or sexual contact
  • e) through cuts and wounds

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

Ans. To reduce the incidence of infectious diseases in my school the precautions will include:

  • (i) Isolating diseased students and clean surroundings
  • (ii) clean food and purified drinking water
  • (iii) not eating junk food and open/uncovered food materials

4. What is immunisation?

Ans. Immunisation is a method of preparing memory cells in immune system. In this method weak or dead microbes of disease are injected in the body such that develop memory lymphocytes(WBCs) but do not cause disease. eg vaccination against polio, tetanus etc.

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?


  • 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.

6.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. If we have fever, headache, stomachache, loose motions, cough and sneeze etc we feel weak. Then we would that we are sick and ought to see a doctor. If only one of these symptoms were present we should still go to see the doctor. Any of these symptoms may be initial signs of a severe disease.

7. 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.


Ans. The long-term effects on our health are likely to be mistune pleasant if we get jaundice because the symptoms severely affect our internal organs and persist for long time.

8. 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. Three most common diseases in my locality are diarrhoea, malaria and tuberculosis and following steps I would suggest to be taken by our local authorities to bring down the incidence of these diseases:

  • i. Supply of safe drinking water and preventing incidences of open drains.
  • ii. Improved and hygienic environment free of garbage and wastes thrown in the open.
  • iii. Eradication of mosquitoes
  • iv. Immunisation/vaccination camps

9. Why are antibiotics not effective for viral disease.

Ans. Antibiotics block the bacterial pathways without affecting the pathways of humans. In the case of viruses, they have very few biochemical pathways of their own. They use the metabolic machinery of host and grow and reproduce.

10.What is inflammation? What are the changes occur during inflammation?

Ans. It is the recruitment process by immune system in which immune system recruits many cells to the affected tissue to kill the disease causing germs.

During this process, certain local effects such as swelling and pain and general effects such as fever may develop.

11.Why do some children fall ill more frequently than others living in the same locality?

Ans. A system which protects our body from diseases and infections is known as immune system. This system is developed in adults due to long term exposure to environment. Children fall ill more frequently because they do not have well developed immune system.

12.How can the disease be prevented?

Ans. Diseases can be prevented by –

  • (a) By presenting exposure to disease causing microbes – For this, exposure to overcrowded areas can be avoided, source of drinking water must be checked, and we must provide clean environments.
  • (b) By consuming proper and sufficient food / balanced diet.
  • (c)By immunization.

13. Give two examples for each of the following:

  • (a) Chronic diseases
  • (b) Infectious diseases
  • (c) Non-infection diseases.

Ans. (a) Chronic diseases – Tuberculosis, arthritis

(b) Infectious diseases – Common cold, Mumps

(c) Non-infectious diseases – Haemophilia, obesity

14. Give difference between vaccines and antibiotics.


15. The body of a patient has lost its power of fighting against infections. Which disease may the patient be suffering from? Name the pathogen and describe any two modes of its transmission from the patient to other person.

Ans. Patient is suffering from AIDS.

It is caused by HIV (Human Immuno deficiency Virus) Modes of transmission are

  • (1) By sexual contact with infected person.
  • (2) By the use infected syringe.

16. What are the means of spread of diseases?

Ans. Diseases spread through –

  • (1) Air – When an infected person sneezes or coughs or spits, a healthy person standing nearby can inhale these droplets, causing infection in that person.
  • (2) By water – Some diseases can spread from one person to another when a sick person’s stools gets into water. The people drinking the infected water thus get the disease.
  • (3) By physical contact – Some of the diseases like AIDS, syphilis and gonorrhea spread by sexual contact. These diseases are not transmitted by casual physical contact like handshakes, hug’s, sports like wrestling and other ways in which we touch other socially.

16. What are the conditions favoring for air-bone diseases?

Ans. Conditions favoring for air-borne infections –

  • a) Close proximity to the infected person.
  • b) Over – crowding
  • c) Poor – Ventilation

17. What are the various dimensions of health?

Ans. Various dimensions of health are–

  • a) Physical dimensions Physical health implies ‘perfect functioning of all the organs and systems of the body.
  • b) Mental dimension – Mental health implies a state of balance and harmony between the individual and surrounding world.
  • c) Social dimension – A person is socially healthy if he has a good job, a good house, a happy family, good neighbors and understanding friends.

18. What are the causes of diseases?

Ans. Causes of diseases are –

  • a) Infection by micro – organisms – Bacteria, virus, fungi, protozoa and worms cause communicable diseases.
  • b) Malfunctioning of body organs.
  • c) Deficiency of one or more nutrients.
  • d) Genetic factors
  • e) Polluted environment.

19. Give the schedule of immunization for infants and children up to six years.

Ans. Schedule of Immunization

20. Explain giving reasons –

  • (a) Balanced diet is necessary for maintaining health body.
  • (b) Health of an organism depends upon the surrounding environmental conditions.

Ans. a) Balanced diet contain all the nutrient required for maintaining proper health as well as needed for growth and repair. Lack of single nutrient causes deficiency diseases.

  • b) surrounding environmental conditions plays an important role in the maintenance of health. For ex we feel depressed if –
  • (i) surrounding are dirty or polluted
  • (ii) garbage is not collected or disposed off
  • (iii) drains are not cleaned and water collects in the streets or open spaces. Unclean surrounding causes the entry of germs via air, water, food or vectors and makes the person unhealthy.

21. What is immunization, immune system, immunity?

Ans. Immunization is a specific method of preventing diseases by inoculating vaccines in the human body.

Immune system – It is a system which protect are body against infection

Immunity – The body’s power to resist and overcome infection is called immunity.

22. Name the agents and the diseases caused by them?


23. What are the different aspects of maintaining good health?

Ans. Different aspects for maintaining good health-

  • a) Community health – It involves all the factors relating to personal health along with the services necessary for providing good health for the community.
  • b) Personal health (hygiene) It is the science of preserving and promoting health mainly through the active efforts of an individual. It is practiced through active, sanitary habits and healthy way of life.
  • c) Exercise, relaxation and sleep. Regular exercise is very necessary to keep the body fit. Proper sleep of about 6-8 hours is essential, Relaxation is very essential for good health.
  • d) Nutrition – Optimum nutrition is essential for maintenance of good health. One should take sufficient and balanced food for maintaining good health.

24. Differentiate between acute diseases and chronic diseases.


25. (a) What is immunisation ?
(b) Define immunity and vaccination.
(c) Define vaccine. .
(d) What type of diseases can be prevented through vaccination ?


  • (a) Immunisation is a process of inoculation (injecting) of substance (vaccine) into a healthy person in order to develop immunity against the disease.
  • (b) Immunity is the ability of a body to recognise, destroy and eliminate external disease-causing agents. This immunisation is done by giving vaccine and thus it is also known as vaccination.
  • (c) The vaccine is a solution containing the disease-causing organisms in a diluted or weakened form. It may have organisms in living or even dead form.This does not actually cause the disease but this would prevent any subsequent exposure to the infecting microbe from turning into actual disease.
  • (d) Protection against diseases like smallpox, rabies, polio, diphtheria, chickenpox and hepatitis is provided through vaccination. It has been possible to eradicate smallpox from all regions of the world through a massive vaccination programme.

26. The signs and symptoms of a disease will depend on the tissue or organ which the microbe targets Justify the statement with two examples.

Ans :- Every microorganism shows its effect on any particular tissue or organ after entering into the body. Thus, there is a change in the structure and function of that tissue or organ. For example, if the lungs are the targets, the symptoms will be cough and breathlessness. If the liver is the target, there will be jaundice. This is called Organ specific manifestation.

Important Questions Class 9th Why Do We Fall ill ~ PDF Download

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Important Questions Class 9th ~ Hindi

No.Chapter Name
1.दो बैलों की कथा
2.ल्हासा की ओर
3.साँवले सपनों की याद
4.नाना साहब की पुत्री देवी मैना को भस्म कर दिया गया
5.प्रेमचंद के फटे जूते
6.मेरे बचपन के दिन
7.साखियाँ एवं सबद
10.कैदी और कोकिला
11.मेरे संग की औरतें
12.रीढ़ की हड्डी

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