NCERT Exemplar Class 9 Science Solutions for Chapter 13 - Why Do We Fall Ill

NCERT Exemplar Solutions Class 9 Science Chapter 13 – Free PDF Download

NCERT Exemplar Solutions for Class 9 Science Chapter 13 Why Do We Fall Ill is a vital study material for the Class 9 students as it has good marks weightage in the final examination. Many times, questions from this chapter are directly asked in competitive examinations as well. Students who are planning to take Biology in their higher secondary school should study this NCERT Exemplar thoroughly in order to understand the topic easily. The NCERT Exemplar Solutions for Class 9 Science Chapter 13 are prepared by highly experienced faculty after conducting vast research on each concept. While solving the textbook questions, students can refer to these solutions to get an overall idea about the topics covered in this chapter.

This NCERT Exemplar Solutions Class 9 Science has answers to questions given in the NCERT Exemplar book. This page presents you with 18 multiple-choice questions, 11 short answer questions and 10 long answer questions. Visit the below link to download the free PDF of these solutions. The solutions can be accessed in both online and offline modes as per the needs of students. The PDF of solutions are available on BYJU’S website, which can be downloaded and used by the students to get their doubts cleared instantly.

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Multiple-choice Questions

1. Which one of the following is not a viral disease?

(a) Dengue

(b) AIDS

(c) Typhoid

(d) Influenza

Soln:

Answer is (c) Typhoid

Explanation:

Typhoid is caused by a bacterium called Salmonella typhi

2. Which one of the following is not a bacterial disease?

(a) Cholera

(b) Tuberculosis

(c) Anthrax

(d) Influenza

Soln:

Answer is (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 the Influenza virus hence option d) is the right answer.

3. Which one of the following diseases is not transmitted by mosquitos?

(a) Brain fever

(b) Malaria

(c) Typhoid

(d) Dengue

Soln:

Answer is (c) Typhoid

Explanation:

Typhoid is transmitted through contaminated food and water.

4. Which one of the following diseases is not caused by bacteria?

(a) Typhoid

(b) Anthrax

(c) Tuberculosis

(d) Malaria

Soln:

Answer is (d) Malaria

Explanation:

Malaria is caused by protozoan called Plasmodium vivax hence d) is the right answer

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

(a) Malaria

(b) Influenza

(c) AIDS

(d) Cholera

Soln:

Answer is (a) Malaria

Explanation:

Malaria is caused by protozoan Plasmodium vivax.

6. Which one of the following has a long term effect on the health of an individual?

(a) Common cold

(b) Chickenpox

(c) Chewing tobacco

(d) Stress

Soln:

Answer is (c) Chewing tobacco

Explanation:

Common cold and chicken pox are acute diseases which will not produce any long-term effects. Stress can be managed and will not have long-term effects. Chewing tobacco is dangerous as it produces long-term effects.

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

Soln:

Answer is (c) Sneezing

Explanation:

Sneezing is a symptom of common and other respiratory diseases which are transmitted through inhalation of contaminated air. Other options provided in the question are not infectious disease; hence they are not transmitted through human contact.

8. AIDS cannot be transmitted by

(a) sexual contact

(b) hugs

(c) breast feeding

(d) blood transfusion

Soln:

Answer is (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.

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

Soln:

Answer is (c) viruses have very few biochemical mechanisms of their own

Explanation:

Antibacterial drugs stop 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.

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

(a) Ascaris

(b) Trypanosoma

(c) Leishmania

(d) Bacteria

Soln:

Answer is (c) Leishmania

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

Soln:

Answer is (c) Airborne diseases

12. Which disease is not transmitted by mosquitoes?

(a) Dengue

(b) Malaria

(c) Brain fever or encephalitis

(d) Pneumonia

Soln:

Answer is (d) Pneumonia

Explanation:

Pneumonia is transmitted through the air and not mosquitos.

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

Soln:

Answer is (d) Living in a large and well-furnished house

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

Soln:

Answer is (d) Acne is not caused by staphylococci

Explanation:

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

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

Soln:

Answer is (b) are vectors for many diseases

Explanation:

Mosquitos are dangerous as they spread disease like Malaria, Dengue, Japanese encephalitis etc.

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

Soln:

Answer is (c) it creates immunity in the body

Explanation:

Vaccines create immunity against the pathogens against which it is designed.

17. Viruses, which cause hepatitis, are transmitted through

(a) air

(b) water

(c) food

(d) personal contact

Soln:

Answer is (b) water

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

Soln:

Answer is (a) animals carrying the infecting agents from sick person to another healthy person.

Short Answer Questions

19. Give two examples for each of the following

(a) Acute diseases

(b) Chronic diseases

(c) Infectious diseases

(d) Non-infectious diseases

Soln:

(a) Acute diseases – Flu, Viral fever

(b) Chronic diseases – Tuberculosis, Elephantiasis

(c) Infectious diseases –Small pox, chicken pox

(d) Non-infectious diseases- Diabetes, Cancer

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

Soln:

Malaria is caused by Plasmodium vivax

Kala-azar is caused by Leishmania

21. Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?

Soln:

Peptic ulcers are caused by bacterium Helicobacter pylori. This bacteria was discovered by Barry J. Marshal and Robin Warren.

22. What is an antibiotic? Give two examples

Soln:

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

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 ———.

Soln:

(a) Pneumonia is an example of Bacterial disease.

(b) Many skin diseases are caused by Fungi.

(c) Antibiotics commonly block biochemical pathways important for the growth of Bacteria.

(d) Living organisms carrying the infecting agents from one person to another are called Vectors.

24. Name the target organs for the following diseases

(a) Hepatitis targets———.

(b) Fits or unconsciousness targets ———.

(c) Pneumonia targets ———.

(d) Fungal disease targets ———.

Soln:

(a) Hepatitis targets Liver.

(b) Fits or unconsciousness targets Brain.

(c) Pneumonia targets Lungs.

(d) Fungal disease targets Skin.

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

Soln:

Edward Jenner discovered the vaccine. Polio and tetanus are the diseases which can be prevented by using vaccines.

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 long 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———.

Soln:

(a) Chronic disease continues for many days and causes long term effect on body.

(b) Acute disease continues for a few days and causes no long term effect on body.

(c) Health is defined as physical, mental and social well-being and comfort.

(d) Common cold is a viral disease.

(e) Many skin diseases are caused by Fungi.

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

Soln:

(a) AIDS – Infectious disease

(b) Tuberculosis – Infectious disease

(c) Cholera – Infectious disease

(d) High blood pressure – non-Infectious disease

(e) Heart disease non – Infectious disease

(f) Pneumonia – Infectious disease

(g) Cancer – non-Infectious disease

28. Name any two groups of micro-organisms from which antibiotics could be extracted.

Soln:

Bacteria and fungi

29. Name any three diseases transmitted through vectors.

Soln:

Malaria transmitted by mosquitos

Rabies transmitted by mad dogs

Elephantiasis is transmitted by mosquitos.

30. Explain giving reasons

(a) Balanced diet is necessary for maintaining healthy body.

(b) Health of an organism depends upon the surrounding environmental conditions.

(c) Our surrounding area should be free of stagnant water.

(d) Social harmony and good economic conditions are necessary for good health.

Soln:

a) Food is essential for the growth and normal functioning of our body. A balanced diet is the one which consists of all the essential nutrients in an appropriate quantity. A balanced diet provides an appropriate amount of biomolecules such as carbohydrates, lipids, proteins, vitamins and minerals which are very essential for our growth and body functioning. Imbalance in the diet leads to many physical and physiological disorders.

b) Health is defined as physical, mental and social well-being and comfort. Health is always dependent on our surroundings and if our environment is unhygienic we get a disease. We get cold and cough in rainy and winter season. Our environmental conditions are very important for being healthy.

c) Stagnant water is the breeding ground for mosquitos. Mosquitos spread many diseases like Malaria, Dengue, Elephantiasis, chikungunya etc. In order to stop the spread of these diseases, our surroundings should be free of stagnant water.

d) Human beings are social organisms. We live in different localities and environments. In order to lead a healthy life, we have to keep our environment clean. We need hygienic food to lead a healthy life which depends on our economic conditions. We often encounter diseases, in order to get the treatment we need the money and our economic status should be strong to afford the treatments.

31. What is a disease? How many types of diseases have you studied? Give examples.

Soln:

Each organ of an organ system has specific functions to do. When this functioning changes or disrupts it leads to a condition called disease. These changes result in some adverse effects on the body’s normal functioning and the changes observed are called signs and symptoms of the disease.

Types of Diseases

Acute:

Diseases that last for only very short periods of time are called acute diseases. Ex: common cold

Chronic:

Diseases that last for a long time, even as much as a lifetime are called chronic diseases. Ex: elephantiasis.

Infectious:

Diseases which are caused by microorganisms are called infectious diseases. These diseases can spread from one person to another by vectors or by other means such as air, food and water. Ex: Typhoid

Non-Infectious:

Diseases that are not caused by infectious agents. Their causes vary, but they are not external causes like microbes that can spread in the community. Instead, these are mostly internal, non-infectious causes. Example: High blood pressure.

32. What do you mean by disease symptoms? Explain by giving two examples.

Soln:

When our body encounters a disease, it results in the abnormal functioning of the body. These abnormal functions are known as symptoms.

For eg., a malaria patient would include symptoms such as high fever with shaking chills, headache, vomiting, nausea, abdominal pain, diarrhoea, etc.

A tuberculosis patient would exhibit symptoms such as fever, chills, loss of appetite, blood in the cough, chest pain, etc.

33. Why is the immune system essential for our health?

Soln:

The immune system is the line of our body. The immune system comprises different kinds of cells that kill the infecting microorganism. When a pathogen enters our body, antibodies are released in response to the pathogen. These antibodies kill pathogens and prevent us from illnesses.

34. What precautions will you take to justify “prevention is better than cure”.

Soln:

Precautions taken to avoid diseases are as follows

1. Maintaining personal as well as public hygiene
2. Awareness about causes, symptoms and the source of diseases
3. Using clean water and avoid storage of water to avoid the growth of mosquitos
4. Balanced diet
5. Regular exercise to boost the immunity
6. Vaccination

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

Soln:

Some of the reasons are listed below.

• Lack of balanced diet leading to malnutrition
• Weak immunity
• Living in congested, unhygienic conditions
• Lack of clean drinking water and hygienic food
• Missing vaccinations

36. Why are antibiotics not effective for viral diseases?

Soln:

Antibiotics act on bacteria and fungi by blocking certain biochemical activities necessary for the living of bacteria. On the other hand, the virus uses the host machinery for survival and replication. Hence, antiviral drugs work differently to antibiotics. They interfere with the viral enzymes to destroy them.

37. Becoming exposed to or infected with an infectious microbe does not necessarily mean developing a noticeable disease. Explain.

Soln:

Our immune system fights disease-causing pathogens and clears them by killing to give us protection from disease. When we get exposed to certain pathogen our immune system sends active cells that kill and clear the pathogen. Owing to our immune system, we don’t often get the disease despite getting exposed to the infectious microbe.

38. Give any four factors necessary for a healthy person.

Soln:

Hygienic environment:

Clean water and a hygienic surrounding can keep us away from water and airborne diseases.

Personal Hygiene:

We should keep our body clean to be healthy.

Food:

Hygienic and nutritious food help to boost the immune system hence a balanced diet is essential for being healthy.

Vaccination:

Vaccination against severe disease is very essential to be healthy.

39. Why is AIDS considered to be a ‘Syndrome’ and not a disease?

HIV AIDS is caused by HIV Virus, which enters our body through body fluids such as blood and breast milk or by sexual means. HIV virus spreads to lymph nodes and it blocks our immune system. This creates a condition where our body cannot fight minor diseases like common cold.

A person with HIV can get pneumonia from the common cold, the minor gut infection may turn into severe diarrhoea. In HIV a person will not have specific symptoms rather he will have a series of infections. Hence HIV is called a syndrome, not a disease.

Class 9 Chapter 13 Why Do We Fall Ill Importance

The chapter Why Do We Fall Ill is designed to teach students about health and hygiene. In this chapter, the students will learn about different diseases, like acute and chronic diseases as well as their causes.  To understand the chapter and to score good marks in the annual exam, students are advised to solve questions from the NCERT Exemplar Class 9 Science Chapter 13.

Subtopics Covered in NCERT Exemplar for Chapter 13 Why Do We Fall Ill

1. Health and Its Failure
   1. The Significance of ‘Health’
   2. Personal and Community Issues Both Matter for Health
   3. Distinctions between ‘healthy’ and ‘disease-free’
2. Disease and Its Causes
   1. What Does Disease Look Like?
   2. Acute And Chronic Diseases
   3. Chronic Diseases and Poor Health
   4. Causes of Diseases
   5. Infectious and Non-infectious Causes
3. Infectious Diseases
   1. Infectious Agents
   2. Means of Spread
   3. Organ-specific and Tissue-specific Manifestations
   4. Principles of Treatment
   5. Principles of Prevention.

To help you understand the concepts covered in Chapter 13, Why Do We Fall Ill, BYJU’S brings you videos, Chapter 13 Class 9 Science Notes, important questions, tips and tricks that will help you excel in Class 9 and various competitive examinations. For more information, visit BYJU’S website or download BYJU’S – The Learning App.