NCERT Exemplar - Why do we fall ill | Chemistry for Class 9 PDF Download

Multiple Choice Questions

Q.1. Which one of the following is not a viral disease?
(a) Dengue
(b) AIDS
(c) Typhoid
(d) Influenza
Ans: (c) Typhoid
Explanation:
Typhoid is caused by a bacterium called Salmonella typhi

Q.2. Which one of the following is not a bacterial disease?
(a) Cholera
(b) Tuberculosis
(c) Anthrax
(d) Influenza

Ans: (d) Influenza

Explanation:

• Cholera is caused by Vibrio cholera
• Tuberculosis is caused by Mycobacterium tuberculosis
• Anthrax is caused by Bacillus anthracis.
• Influenza is caused by Influenza virus hence option d) is the right answer.

Q.3. Which one of the following disease is not transmitted by mosquito?
(a) Brain fever
(b) Malaria
(c) Typhoid
(d) Dengue

Ans: (c) Typhoid
Explanation:
Typhoid is transmitted through contaminated food and water.

Q.4. Which one of the following diseases is not caused by bacteria?
(a) Typhoid
(b) Anthrax
(c) Tuberculosis
(d) Malaria
Ans: (d) Malaria
Explanation:
Malaria is caused by protozoan called Plasmodium vivax hence d) is the right answer

Q.5. Which one of the following diseases is caused by protozoans?

(a) Malaria

(b) Influenza

(c) AIDS

(d) Cholera
Ans: (a) Malaria
Explanation:
Malaria is caused by protozoan Plasmodium vivax.

Q.6. Which one of the following has a long term effect on the health of an individual?
(a) Common cold
(b) Chicken pox
(c) Chewing tobacco
(d) Stress
Ans: (c) Chewing tobacco
Explanation:
Common cold and chicken pox are acute diseases which will not produce any long term effect. Stress can be managed and will not have long term effect. Chewing tobacco is dangerous as it produces a long term effect.

Q.7. Which of the following can make you ill if you come in contact with an infected person?
(a) High blood pressure
(b) Genetic abnormalities
(c) Sneezing
(d) Blood cancer
Ans: (c) Sneezing
Explanation:
Sneezing is a symptom of common and other respiratory diseases which are transmitted through inhalation of contaminated air. Other option provided in the question are not infectious disease, hence they are not transmitted through human contact.

Q.8. AIDS cannot be transmitted by
(a) sexual contact
(b) hugs
(c) breast feeding
(d) blood transfusion
Ans: (b) hugs
Explanation;
AIDS is transmitted by the exchange of body fluids. When we hug each other there cannot be an exchange of any body fluid hence AIDS cannot be transmitted by hugs.

Q.9. 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

Explanation:
Antibacterial drugs stop the certain biochemical reaction in the bacteria that kills the bacteria. But in viruses there are a few biochemical processes which are difficult to target hence making anti-viral drugs is difficult.

Q.10. Which one of the following causes kala-azar?
(a) Ascaris
(b) Trypanosoma
(c) Leishmania
(d) Bacteria
Ans: (c) Leishmania

Q.11. If you live in an 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) Airborne diseases

Q.12. Which disease is not transmitted by mosquitoes?

(a) Dengue

(b) Malaria

(c) Brain fever or encephalitis

(d) Pneumonia
Ans: (d) Pneumonia
Explanation:
Pneumonia is transmitted through the air and not mosquitos.

Q.13. 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

Q.14. 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
Explanation:

(d) is wrong because acne is a bacterial skin infection which is caused by staphylococci.

Q.15. We should not allow mosquitoes to breed in our surroundings because they
(a) multiply very fast and cause pollution
(b) are vectors for many diseases
(c) bite and cause skin diseases
(d) are not important insects
Ans: (b) are vectors for many diseases
Explanation:
Mosquitos are dangerous as they spread disease like Malaria, Dengue, Japanese encephalitis etc.

Q.16. You are aware of Polio Eradication Programme in your city. Children are vaccinated because
(a) vaccination kills the polio causing microorganisms
(b) prevents the entry of polio causing organism
(c) it creates immunity in the body
(d) all the above
Ans: (c) it creates immunity in the body
Explanation:
Vaccines create immunity against the pathogens against which it is designed.

Q.17. Viruses, which cause hepatitis, are transmitted through
(a) air
(b) water
(c) food
(d) personal contact

Ans: (b) water

Q.18. Vectors can be defined as
(a) animals carrying the infecting agents from sick person to another healthy person
(b) microorganisms which cause many diseases
(c) infected person
(d) diseased plants
Ans: (a) animals carrying the infecting agents from sick person to another healthy person.

Short Answer Type Questions 

Q.19. Give two examples for each of the following:
(a) Acute diseases
(b) Chronic diseases
(c) Infectious diseases
(d)Non-infectious diseases
Ans: (a) Influenza, Viral fever
(b) Tuberculosis (T.B.), Elephantiasis
(c) Chicken pox, Smallpox
(d) Goitre, Diabetes

Q.20. Name two diseases caused by Protozoans. What are their causal organisms?
Ans: (a) Sleeping sickness caused by Trypanosorrn gambiense.
(b) Kala-azar caused by Leishmania donovani.

Q.21. Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?
Ans: Helicobacter pylori bacterium causes peptic ulcers.
Barry Marshall and Robin Warren discovered the pathogen for the first time.

Q.22. What is an antibiotic? Give two examples

Ans. Antibiotic is a chemical agent that kills the bacteria or fungi by blocking their biochemical pathway. Ex: Streptomycin, Azithromycin.

Q.23. Fill in the blanks:
(a) Pneumonia is an example of ________ disease.
(b) Many skin diseases are caused by _______ .
(c) Antibiotics commonly block biochemical pathways important for the growth of_______.
(d) Living organisms carrying the infecting agents from one person to another are called_______.
Ans: (a) communicable
(b) fungi
(c) bacteria
(d) vectors

Q.24. Name the target organs for the following diseases
(a) Hepatitis targets _______.
(b) Fits or unconsciousness targets________.
(c) Pneumonia targets________.
(d) Fungal disease targets________.
Ans:
(a) liver
(b) brain
(c) lungs
(d) skin

Q.25. Who discovered 'Vaccine' for the first time? Name two diseases which can be prevented by using vaccines.
Ans: Edward Jenner discovered ‘vaccine’ for the first time.
The diseases can be prevented by using vaccines are — Diphtheria and Polio.

Q.26. Fill in the blanks:
(a)______disease continues for many days and causes______on body.
(b)_______disease continues for a few days and causes no longer term effect on body.
(c)________is defined as physical, mental and social well-being and comfort.
(d) Common cold is______disease.
(e) Many skin diseases are caused by________.
Ans: (a) Chronic, long-term effect
(b) Acute
(c) Health
(d) infectious (communicable)
(e) fungi

Q.27. Classify the following diseases as infectious or non-infectious.
(a) AIDS
(b) Tuberculosis
(c) Cholera
(d) High blood pressure
(e) Heart disease
(f) Pneumonia
(g) Cancer
Ans: (a) infectious
(b) infectious
(c) infectious
(d) non-infectious
(e) non-infections
(f) infectious
(e) non-infectious

Q.28. Name any two groups of microorganisms from which antibiotics could be extracted.
Ans: Bacteria and fungi.

Q.29. Name any three diseases transmitted through vectors.
Ans: Malaria (vector - Anopheles), Dengue (vector - Aedes) and Kala-azar (vector - Sandfly)

Long Answer Type Questions 

Q.30. Explain giving reasons:
(a) Balanced diet is necessary for maintaining healthy body.
Ans: Balanced diet is required for maintaining a healthy body. It provides raw materials and energy in appropriate amount which is needed for the substances such as carbohydrates, protein, fats, minerals, etc., that in turn are essential for the proper growth and functioning of the healthy body.
(b) Health of an organism depends upon the surrounding environmental conditions.
Ans: Health of an organism depends upon the surrounding environmental conditions. It is a state of being well enough to function well physically, mentally and socially. These conditions depend upon the surrounding environmental conditions. If there is unhygienic conditions in surrounding area, it is likely we might get infected or diseased.
(c) Our surrounding area should be free of stagnant water.
Ans: Our surrounding area should be free of stagnant water because many water borne diseases and insect vectors flourish in stagnant water that cause diseases in human beings.
(d) Social harmony and good economic conditions are necessary for good health.
Ans: Human beings live in societies and different localities like villages or cities which determines the social and physical environment. Hence, both are to be kept in harmony. Public cleanliness is important for individual health. We need good food for healthy body for better living conditions and for the treatment of diseases the economic conditions should also be good.

Q.31. What is a disease? How many types of diseases have you studied? Give examples.
Ans: When the functioning or the appearance of one or more systems of the body change for the worse, then there is a disease.
Examples: Influenza, tuberculosis, pneumonia (infectious), cancer (non-infectious), etc. Types of Diseases:
(a) Acute and chronic on the basis of duration. Acute disease — Common cold Chronic disease — Tuberculosis of lungs
(b) Congenital and acquired on the basis of period of occurrence.
Congenital disease — Colour blindness
Acquired disease — Malaria
Acquired diseases are of two kinds — Infectious and
non-infectious on the basis of causal agent.
Infectious disease — Typhoid
Non-infectious disease — Cancer

Q.32. What do you mean by disease symptoms? Explain giving two examples.
Ans: When the functioning or the appearance of one or more systems of the body change for the worse, it gives certain abnormal signs of the disease. These visual changes in human beings with indication of the presence of a particular disease is called disease symptoms.
Examples:
(a) Skin lesions are the symptoms of Chickenpox.
(b) Cough is the symptom of lung infection.

Q.33. Why is immune system essential for our health?
Ans: The immune system is essential for our health as it functions as a defensive mechanism to fight against pathogenic microbes. It has cells that are specialised to kill infecting microbes and keep our body healthy.

Q.34. What precautions will you take to justify “Prevention is better than cure”?
Ans: Following precautions should be taken for prevention of disease:
(a) Maintaining hygienic conditions.
(b) Awareness about the disease and causal organism.
(c) Proper nutrition with balanced diet, clean food and water.
(d) Regular medical check up.
(e) Regular exercise and relaxation.

Q.35. Why do some children fall ill more frequently than others living in the same locality?
Ans: Some children fall ill more frequently due to poor domestic and personal hygiene, unclean food and lack of proper nutrition and balanced diet. Due to these immune systems become weak.

Q.36. Why are antibiotics not effective for viral disease?
Ans: Antibiotics arc not effective for viral diseases as they block the biosynthetic pathways of the microbes/bacteria. However, viruses have very few biochemical mechanisms of their own and hence are unaffected by antibiotics.

Q.37. Becoming exposed to or infected with an infectious microbe does not necessarily mean developing noticeable disease. Explain.
Ans: Infected with a microbe does not mean developing a disease because an infectious microbe is able to cause a disease only if the immune system of the person is weak and a person with strong immune system normally fights off microbes. We have cells which are specialised to kill the pathogenic microbes. These cells are active when infecting microbes enter the body and if they are successful in removing the pathogen, we remain disease-free. So, even if we are exposed to infectious microbes, the person will not catch the disease.

Q.38. Give any four factors necessary for a healthy person.
Ans: Factors necessary for a healthy person are as follows:
(a) A clean environment with proper public health services.
(b) Personal hygiene prevents infectious diseases.
(c) A proper balanced diet and sufficient nourishment are necessary for good immune system of our body.
(d) Immunisation/vaccination against severe diseases.

Q.39. Why is AIDS considered to be a ‘Syndrome’ and not a disease?
Ans: AIDS is considered a syndrome and not a disease because AIDS causing virus—HIV comes into the body via the sexual organs or any other means like blood transfusion and spread to lymph nodes all over the body. The virus damages the immune system of the body and the body can no longer fight off even minor infections. Instead, every small cold can become pneumonia, or minor gut infection can become severe diarrhoea. The effect of disease becomes very severe and complex, at times killing the person suffering from AIDS. Hence, there is no specific disease symptoms for AIDS but it results in a complex diseases and symptoms.