Courses for Kids
Free study material
Offline Centres
Store Icon

Important Questions for CBSE Class 9 Science Chapter 13 - Why Do We Fall ill

Last updated date: 23rd Apr 2024
Total views: 659.7k
Views today: 11.59k

CBSE Class 9 Science Chapter-13 Important Questions - Free PDF Download

Important questions science class 9 chapter 13 are prepared by the experts of Vedantu. Students are provided with ultimate study materials to perform better in the examination. Science chapter 13 why do we fall ill of class 9 deals with the health of a human being. It teaches the importance to stay healthy and prevent us from falling sick. It focuses on the significance of staying fit and healthy. It casts light on the importance of daily hygiene to keep diseases at bay. Register Online for Class 9 Science tuition on to score more marks in your examination. Vedantu is a platform that provides free CBSE Solutions (NCERT) and other study materials for students. Maths Students who are looking for the better solutions ,they can download Class 9 Maths NCERT Solutions to help you to revise complete syllabus and score more marks in your examinations.

Download CBSE Class 9 Science Important Questions 2024-25 PDF

Also, check CBSE Class 9 Science Important Questions for other chapters:

CBSE Class 9 Science Important Questions


Chapter No

Chapter Name


Chapter 1

Matter in Our Surroundings


Chapter 2

Is Matter Around Us Pure


Chapter 3

Atoms and Molecules


Chapter 4

Structure of Atom


Chapter 5

The Fundamental Unit of Life


Chapter 6



Chapter 7

Diversity in Living Organisms


Chapter 8



Chapter 9

Force and Laws of Motion


Chapter 10



Chapter 11

Work and Energy


Chapter 12



Chapter 13

Why Do We Fall ill


Chapter 14

Natural Resources


Chapter 15

Improvement in Food Resources

Popular Vedantu Learning Centres Near You
Mithanpura, Muzaffarpur
location-imgVedantu Learning Centre, 2nd Floor, Ugra Tara Complex, Club Rd, opposite Grand Mall, Mahammadpur Kazi, Mithanpura, Muzaffarpur, Bihar 842002
Visit Centre
Anna Nagar, Chennai
location-imgVedantu Learning Centre, Plot No. Y - 217, Plot No 4617, 2nd Ave, Y Block, Anna Nagar, Chennai, Tamil Nadu 600040
Visit Centre
Velachery, Chennai
location-imgVedantu Learning Centre, 3rd Floor, ASV Crown Plaza, No.391, Velachery - Tambaram Main Rd, Velachery, Chennai, Tamil Nadu 600042
Visit Centre
Tambaram, Chennai
location-imgShree Gugans School CBSE, 54/5, School road, Selaiyur, Tambaram, Chennai, Tamil Nadu 600073
Visit Centre
Avadi, Chennai
location-imgVedantu Learning Centre, Ayyappa Enterprises - No: 308 / A CTH Road Avadi, Chennai - 600054
Visit Centre
Deeksha Vidyanagar, Bangalore
location-imgSri Venkateshwara Pre-University College, NH 7, Vidyanagar, Bengaluru International Airport Road, Bengaluru, Karnataka 562157
Visit Centre
View More
Watch videos on
Important Questions for CBSE Class 9 Science Chapter 13 - Why Do We Fall ill
👌Term 2 Super Revision -🤒Why Do We Fall Ill? | CBSE Class 9 Biology Revision | Vedantu 9 & 10 Hindi
Vedantu 9&10
2 years ago
Download Notes
yt video
Why Do We Fall Ill in One Shot[Full Chapter] CBSE Class9 Biology/Science Chapter 13 | Term 2 Vedantu
Vedantu 9&10
2 years ago
Play Quiz
yt video
Why do We Fall Ill? CBSE Class 9 Biology | Science Chapter 13 NCERT | CBSE in One Shot | Vedantu
Vedantu 9&10
3 years ago
Play Quiz
Download Notes
yt video
Why Do we Fall Ill in One Shot | CBSE Class 9 Biology | Science Chapter 13 | NCERT | Vedantu
Vedantu 9&10
4 years ago
Play Quiz
Download Notes

Study Important Questions for Class 9 Science Chapter 13 - Why Do We Fall Ill

Very Short Answer Questions (1 Mark)

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

  1. Living in clean space

  2. Good economic condition

  3. Social equality and harmony

  4. Living in a large and well-furnished house.

Ans: a. Living in clean space

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

  1. Alexander Fleming 

  2. Edward Jenner

  3. H.G. Khorana

  4. William Harvey.

Ans: a. Alexander Fleming

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

  1. Viruses make use of host machinery.

  2. Viruses are on the border line of living and non-living

  3. Viruses have very few biochemical mechanisms of their own

  4. Viruses have a protein coat.

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

4. Which one of the following deficiency disease?

  1. Diabetes

  2. Malaria

  3. Goitre

  4. Tetanus

Ans: c. Goitre

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

  1. Vaccines

  2. Microbes

  3. Antibiotics

  4. fungi

Ans: c. antibiotics

6. Choose the wrong statement –

  1. High blood pressure is caused by excessive weight and lack of exercise.

  2. Cancers can be caused by genetic abnormalities.

  3. Peptic ulcers are caused by eating acidic food.

  4. Acne is not caused by staphylococci.

Ans: d. Acne is not caused by staphylococci.

7. Rabies occurs through the bite of.

  1. Female Anopheles Mosquito

  2. Female culex mosquito

  3. Rabid dog

  4. housefly.

Ans: c. Rabid dog

8. AIDS is caused by –

  1. Bacteria

  2. Virus

  3. Protozoa

  4. Fungi

Ans: b. Virus

9. Identify a protozoan disease –

  1. Ringworm

  2. Measles

  3. Diphtheria

  4. 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.

  1. Cancer

  2. AIDS

  3. Air borne diseases

  4. Cholera.

Ans: c. Air borne diseases

11. The symptom of goitre is

  1. Swelling of eye

  2. Swelling of the thyroid gland

  3. Swelling of the liver

  4. 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?

  1. Use of disposable syringes.

  2. Safe sex practiced between single partners.

  3. Proper screening of blood before transfusion

  4. 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 –

  1. vaccination kills polio causing micro-organisms

  2. Prevents the entry of polio causing micro-organisms

  3. It creates immunity in the body.

  4. all the above.

Ans: c. It creates immunity in the body.

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

  1. Diarrhoea

  2. Cholera

  3. Pneumonia

  4. Tuberculosis

Ans: c. Pneumonia

15. Which one is not sexually transmitted disease?

  1. AIDS

  2. Gonorrhoea

  3. Syphilis

  4. Diabetes.

Ans: d. Diabetes.

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

  1. Ascaris

  2. Trypanosome

  3. Leishmania

  4. Bacteria

Ans: c. Leishmania

Short Answer Questions (2 Marks) 

1. State any two conditions essential for good health.

Ans: The two conditions essential for good health are:

i. Clean and Hygienic surroundings

ii. A sound physical, mental and social state

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

Ans: The two conditions essential for being free of disease are:

i. Personal as well as domestic hygiene

ii. Consuming a balanced diet

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

Ans: The answers to the above questions are different as a person may be disease free but does not have a good physical, mental or social state which lead to a poor health.

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 order to avoid any of/most of the above illnesses.

Ans: I fell ill twice last year. I had suffered from viral fever and typhoid.

In order to prevent myself from getting infected again in future, I will avoid street food especially those cooked at unhygienic places and are kept uncovered. Also, I will drink filtered or boiled water.

b. Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.

Ans: In order to prevent myself from getting infected again in future, I shall keep my surroundings cleaner than earlier and also maintain my personal hygiene.

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 prevent themselves from getting sick as they take proper care of their personal hygiene as well as domestic hygiene. Also, they maintain clean and immune surroundings to prevent the spread of 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?

Ans: If the baby is crying continuously and remains restless for a long time despite providing comfort then he/she might be sick.

b. What is the sickness?

Ans: We should observe the symptoms and its severity 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 must have consumed a limited diet and hence less nutrition is given to her body. Also, she is at a high risk of getting infected from chicken-pox while taking care of someone suffering from it. Therefore, we can state that her health is poor and she is very likely to fall sick again.

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 our friend is suffering from measles since measles is an infectious/communicable disease which can be easily spread from person to person.

9. How are acute diseases different from chronic diseases?

Ans: Acute disease are diseases which are sudden but severe and last for short periods of time. For example: Malaria, Jaundice, etc.

Chronic disease are diseases which develop gradually over a period of time and are long lasting causing damage to the organs of the body. For example: Cancer, Diabetes, etc.

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

Ans: The full form of AIDS is Acquired Immune Deficiency Syndrome. AIDS is caused by HIV – Human Immunodeficiency virus.

11. Define the following terms:

(a) health

Ans: Health is defined as a sound state of physical, mental and social well-being and it does not relate to the absence of disease.

(b) disease.

Ans: Disease refers to the malfunctioning of the organs or parts of the body due to internal dysfunctions or external factors.

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

Ans: Non-communicable diseases are non-infectious diseases which cannot be spread from one person to another and are long-lasting.

For example – Diabetes, cancer.

13. Define carriers. Give two examples.

Ans: Carriers are the organisms that carry disease causing agents and has the ability to spread the disease amongst healthy individuals without showing any sign of disease

For example – Housefly, female insect Anopheles.

14. Why do children need vaccination?

Ans: Vaccination is important for children because it protects them from getting infected by deadly diseases like tetanus, polio and also prevents the spread of these diseases from child to child.

15. How can we prevent influenza?

Ans: Influenza is an air-borne disease, therefore it can be prevented by maintaining a distance from the others and washing your hands regularly.

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

  1. Health is only the absence of any physical disease.

Ans: This statement is incorrect because health is a state of sound physical, mental and social well-being. Hence, being disease free does not ensure that the person has a good health.

  1. Children need not be immunized.

Ans: This statement is incorrect because there is a need to immunize children as their immune system is not fully developed and so they are more susceptible to diseases.

17. What is peptic ulcer?

Ans: Peptic ulcer is a disease in which ulcers or sores are formed on the lining of your stomach or duodenum and the person suffers from pain due to acidity.

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

Ans: Diseases are broadly classified into two types –

  1. Communicable or infectious disease – Those diseases which are spread from one person to another in contact and it generally lasts for a short term. It can be spread through air, water, food, physical contact and insects. 

For example: Chicken pox, malaria, cholera, etc.

  1. Non-communicable or non- infectious diseases – Those diseases which cannot be spread from person to person and are long-lasting. For example - arthritis, marasmus etc.

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

Ans: Helicobacter pylori bacterium causes peptic ulcers and it was discovered by Robin Warren and Barry Marshall.

20. Name the target organs for the following disease-

  1. Hepatitis targets ______________

Ans: liver

  1. Fits or unconsciousness targets __________________

Ans: brain

  1. Pneumonia targets _________________

Ans: lungs

  1. Fungal disease targets ______________

Ans: skin

21. How are diseases diagnosed by physician?

Ans: When a person is infected from a disease, it may cause malfunctioning of organs or body parts which produces external symptoms of diseases. On the basis of the symptoms and physical examination of the person, the disease is diagnosed by the physician.

22. 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.

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

Ans: Infectious diseases can be treated by two ways:

  1. By reducing its effect using medications that may reduce its symptoms.

  2. By killing its cause using antibiotics.

Short Answer Questions (3 Marks)

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

Ans: When we are sick, our body becomes fragile and our digestion process also becomes poor. Hence, we are advised to take bland and nourishing food when we are sick because we need complete nourishment for faster recovery.

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

Ans: Infectious diseases can spread by the following means:

  1. Through contaminated food and water

  2. Through atmosphere

  3. Through vectors or carriers (housefly, mosquito etc)

  4. Through direct skin contact or sexual contact

  5. Through cuts or 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, I would take the following precautions in my school:

  1. Maintain distance from an infected person

  2. Keep my surroundings clean

  3. Wash my hands regularly.

  4. I would not consume open/uncovered food materials

4. What is immunisation?

Ans: Immunisation is a method in which an immunized person develops resistance towards a specific disease. 

In this method weak or dead microbes of a specific disease are injected into the body such that they develop memory lymphocytes (WBCs) but do not cause disease. For example: 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?

Ans: The immunisation programmes available at the nearest health centre in our locality are as follows:

  1. For infants: DPT, polio, measles

  2. For children: TT, TAB, smallpox

  3. Hepatitis-B for pregnant women

The diseases like typhoid, measles, smallpox, polio 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 continuous headache, stomach ache, loose motions, fever, cough and cold, then we would consult a doctor. If only one of these symptoms were present continuously for a period of time then also we will go to see the doctor as it may be the 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?

  1. if you get jaundice

  2. if you get lice

  3. if you get acne.


Ans: If I suffer from jaundice, I believe that its long-term effects on our health are likely to be most unpleasant because the symptoms severely affect our body parts and the internal organs and persist for a 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. 

To bring down the incidence of these diseases I would suggest the following steps:

  1. Supply of safe drinking water and closed drains.

  2. Hygienic and clean environment.

  3. Eradication of mosquitoes

  4. Immunisation or vaccination camps

9. Why are antibiotics not effective for viral disease.

Ans: Viruses are different from bacteria. They do not have cell walls which can be attacked by antibodies. Thus, antibodies are ineffective against viral disease. Antibiotics tend to break the bacterial cell wall and block the bacterial pathways. Thus, they are effective on bacterial infections.

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

Ans: Inflammation is a process carried by the immune system in which it recruits many cells to the affected tissue during an injury or burn to kill the disease-causing germs and protect the tissue from external pathogens.

During this process, swelling, pain and redness may develop.

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

Ans: It is the immune system which protects our body from various diseases and infections. Children tend to fall ill more frequently because they have a poor or not a well-developed immune system.

A balanced diet, proper sleep and exercise would help children develop a strong immune system.

12. How can the disease be prevented?

Ans: Diseases can be prevented by taking the following measures–

  1. By avoiding crowded places

  2. By maintaining public hygiene

  3. By washing our hands regularly

  4. By consuming a balanced diet and maintaining personal hygiene.

  5. By immunization.

13. Give two examples for each of the following:

  1. Chronic Diseases

Ans: Chronic diseases – Diabetes, arthritis

  1. Infectious Diseases

Ans: Infectious diseases – Chicken pox, Influenza

  1. Non-infectious Diseases.

Ans: Non-infectious diseases – asthma, obesity

14. Give difference between vaccines and antibiotics.

Ans: Difference between vaccines and antibiotics is stated as follows:



Vaccines are the suspension of weak or dead microbial agents of the same disease in a person so that he is immune against that disease.

Antibiotics are medicines made by living microbes and it may be used for one or more diseases.

They are given before the person gets infected in order to prevent him.

They are given after the person gets infected from a disease.

They provide immunity or protection for a longer period.

Antibiotics provide protection for a short period of time.

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: The patient is suffering from AIDS, i.e., Acquired Immune Deficiency Syndrome. 

AIDS is caused by HIV – Human Immunodeficiency virus.

Two modes of transmission are

  1. By sexual contact with an infected person.

  2. By the use of an infected syringe or needle.

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

Ans: Conditions favouring for air-borne infections -

  1. Close contact with the infected person.

  2. Over – crowding

  3. Poor – Ventilation

17. What are the various dimensions of health?

Ans: Various dimensions of health are as follows–

  1. Physical Dimensions- It implies perfect functioning of all the organs and parts of the body.

  2. Mental Dimensions – It implies a state of mental balance, harmony and peace between the individual and his environment.

  3. Social Dimensions – A person is socially sound if he shares a good bond with his surroundings and the people around him, i.e., if he has a good job, a good house, a happy family, helpful friends.

18. What are the causes of diseases?

Ans: Causes of diseases are –

  1. Microorganisms – Bacteria, virus, fungi, protozoa and worms cause most of the communicable diseases.

  2. Malfunctioning of parts of the body or body organs.

  3. Nutritional deficiency.

  4. Genetic factors.

  5. Polluted environment.

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

Ans: The schedule of immunization for infants and children up to six years is given below:



No. of doses


3-9 months


3 doses at intervals of 1-2 months


3 doses at intervals of 1-2 months



9-12 months



18-24 months


1 (booster)


1 (booster)


5-6 years



20. Explain giving reasons –

  1. Balanced diet is necessary for maintaining health body.

Ans: Balanced diet contains all the nutrients required for maintaining proper health as well as they are needed for growth and repair of the damaged cells.

  1. Health of an organism depends upon the surrounding environmental conditions.

Ans: Surrounding environmental conditions plays an important role in the maintenance of health. For example we feel uneasy if –

  1. Our surroundings are dirty and the garbage is not collected or disposed off.

  2. Drains are not cleaned and water gets collected in the streets or open spaces. 

21. What is immunization, immune system, immunity?

Ans: Immunisation is a method in which an immunized person develops resistance towards a specific disease. 

Immune system is a system which protects the body against pathogens which may lead to infections.

Immunity refers to our body’s power to resist and overcome infection.

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

Ans: A list of agents and the disease caused by them is given below:


Disease Caused


Tuberculosis, whooping cough


AIDS, chicken pox, Common cold


Skin infection, ringworm, athlete’s foot


Sleeping-sickness, Malaria, amoebic dysentery


Giardiasis, Amebiasis

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

Ans: Different aspects for maintaining good health-

  1. Community health – Keeping our surrounding clean and hygienic contributes to our personal health.

  2. Maintaining personal hygiene by washing our hands continuously and avoiding close contact and overcrowded places. 

  3. Regular exercise and a proper sleep are very necessary to keep the mind and body fit. Also, relaxation is very essential for good health.

  4. Optimum nutrition through a balanced diet is essential for maintenance of good health. One should avoid the consumption of junk food to maintain good health.

CBSE Class 9 Science Chapter 13 Important Questions - Free PDF Download

The Importance of Health

Health is the state of being well enough to function well physically, mentally as well as socially. Health cannot be achieved entirely on our own because it depends on the surrounding the organism. 

The surrounding has a great impact on the health of a human being. Human beings live in a society. Consider what would happen if there is no garbage collector to collect the garbage and everyone throw garbage around their houses. Within a few days, the place will start to stink and everyone will fall sick. This will have a huge impact on the physical, mental as well as on the social health of the people living in that area.

We need food to stay healthy and fit. Food can be earned by doing work. For this, there should be opportunities to do work. One also needs to stay happy to be healthy. Happiness can cure many illnesses and it gives mental as well as physical fitness to the body. Social equality and harmony also play a very pivotal role in the health of an individual.

The Difference Between Staying Healthy and Disease Free

Disease means being uncomfortable. When we see a person suffering from a disease we can find a particular cause for the discomfort. But whereas when a person is not in a good health we cannot find the actual suffering from any disease. 

In simple words, not being diseased is not the same as being healthy. When we think about good health then we think about societies and also communities. On the other hand, when we think about a disease we always think about the suffering of an individual.

Types of Disease

There are two types of disease. One is an acute disease and the other one is a chronic disease. The disease which lasts for a very short period is known as acute diseases. Common cold or viral fever is an example of an acute disease. 

The diseases which last for a very long period are known as a chronic disease. Chronic diseases can also last for a lifetime.  The infections causing elephantiasis which is very common in the parts of India and Africa is an example of chronic disease.

Any disease can have a great effect on the health of an individual. An acute disease that gets over in a very short period does not have a major impact on the health of a human being. Whereas chronic diseases which take a very long period sometimes the whole life have a very great impact on the body. Chronic disease disrupts the mental health of the individual.

Causes of a Disease

There are two types of causes of disease. One is the infectious cause and the other is the non-infectious cause. It is very crucial to keep public health as well as community health in mind when one thinks about the cause of the disease. When microbes or microorganisms are the reason behind a disease then that disease is known as infectious disease. 

The microbes spread in the community and also the disease they cause also spreads with them. Conductivities are an example of an infectious disease. On the other hand, some diseases are not caused by infectious agents such as microorganisms. Such diseases are called non-infectious diseases. The causes of non-infectious diseases vary with the situation. 

For example, cancer is a type of non-infectious disease because it is caused by genetic abnormalities. High blood pressure is also an example of a non-infectious disease because it is caused by excessive weight and lack of exercise.

The prevention, treatment, and causes of disease at the community level will be different for different diseases.

Means of Spread of a Disease

Diseases can be spread in very different ways. Different diseases are spread in different ways. Some diseases spread through water. When the excreta from someone suffering from an infectious gut disease such as cholera gets mixed with the drinking water then the person drinking that water gets cholera. 

The microbes causing cholera will enter the body of the person drinking and will have a huge impact on the health of the human being. Such diseases are usually spread when there are no safe drinking water supplies.

The sexual act is one of the closest physical contacts between two people. Infectious diseases like AIDS or Syphilis are transmitted by sexual contact from an infected partner. AIDS can also spread through the blood to blood contact with the infected person. It can also spread from an infected mother to the baby during the pregnancy or through breastfeeding. Casual physical contact such as handshakes, hugs, or wrestling can also cause communicable disease if a healthy person comes in contact with an infected person.

Humans live in an environment that is full of various creatures. Many diseases are spread through various animals to humans. Some animals carry infectious agents from a sick person to another potential host. Such animals are the intermediaries and are called vectors. Mosquitoes are the vectors that transfer the disease from an infected person to a healthy person.

Principles of Treatment

One way to treat disease will be to reduce the effect of the disease and the other way will be to kill the cause of the disease. In the first case, we provide with required treatment that will reduce the symptoms of the disease. The symptoms usually occur because of the inflammation. For example, when we have a fever we take medicines and take bed rest.

The other way is to kill the microbes causing the disease. Microbes can be classified into different categories like viruses, bacteria, fungi, or protozoa. These microbes causing illness are killed by using anti-bacterial medicines or anti-viral medicines. It is hard to make an antiviral drug but it is easy to make an anti-bacterial drug. 

Viruses have few biochemical mechanisms. They enter the cell of a human being and use the machinery for their life process. This means there are few virus-specific targets to aim at. 

Despite these limitations are very few effective antiviral drugs because of the development in medical science. There are anti-viral drugs to keep HIV infections under control.

Why Study Important Questions class 9 from Vedantu?

Vedantu is one of the best education platforms where all the study materials are procured by experts. Why do we fall ill class 9 important questions are prepared by Vedantu especially for the students to get a clear concept of the topics. 

Vedantu's important questions for class 9 chapter 13 tell the students about what type of questions they should expect to face in their exams. All the questions provided by us are available online as well as online. One can go through the notes and also the questions to practice and get a revision anytime. 

The important questions for class 9 are prepared by the most experienced teachers of Vedantu also help every student to revise for the upcoming exams. Students can practice with questions to score good marks in the upcoming examination. Why do we fall ill class 9 important questions are provided to the students for their better understanding.

Important Related Links for CBSE Class 9 

FAQs on Important Questions for CBSE Class 9 Science Chapter 13 - Why Do We Fall ill

1. Write a Short Note on Peptic Ulcers.

Ans: For many long years people use to think that peptic ulcers are caused because of the lifestyle reasons of an individual. Peptic ulcers are a disease that causes acidity related pain as well as bleeding in the stomach and duodenum. This leads to indigestion in the stomach of the individual suffering from peptic ulcers. 

Everyone used to think that too much stress led to a lot of acid secretion in the stomach which causes peptic ulcers. Then two Australians discovered that a bacterium named Helicobacter pylori was responsible for causing peptic ulcers in the stomach. 

Robin Warren born in 1937 and Barry Marshall born in 1951 who was a young clinical fellow made this discovery. A peptic ulcer is not a chronic disease. It is a disease that can be cured in a short period with antibiotics.

2. Write in Brief about Immunization.

Ans: The traditional Indian as well as the Chinese medicinal systems sometimes deliberately rubbed the skin crusts from smallpox victims into the skin of the healthy person. This was done to create a resistance against the disease into the body of the healthy person. 

Two centuries ago an English physician named Edward Jenner realized that maids who have cowpox did not catch smallpox. Cowpox is a very mild disease. Jenner then deliberately gave cowpox to people and found out that it was a resistance to smallpox. 

This happened because the smallpox virus was very closely related to the cowpox virus. ‘Cow’ is ‘Vacca’ in Latin and cowpox is ‘vaccinia’ and this is how the word ‘vaccination’ came into usage.

3. Name any two groups of microorganisms from which antibiotics could be extracted.

Ans: Antibiotics are pharmaceutical drugs, produced to destroy or prevent the growth of the disease-causing bacteria in the human and animal body. Bacteria and Fungi are two groups of microorganisms that help make antibiotics. Various variants of bacteria and fungi are used in making antibiotics merged along with different chemicals that can effectively treat a particular illness. Antibiotics are of numerous types like tablets, syrups, and capsules and are consumed in different manners.

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

Ans: Sickness results in weak digestion and low immunity, so doctors recommend us to take bland food that is easy on our stomach and nourishing food that refuels our immune system. Fruits and other edibles rich in vitamins are also suggested for a rapid recovery. It is essential to take easy-to-digest and fulfilling food along with the prescribed medicines for a quick recovery. Though the type of food intake may differ for certain illnesses.

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

Ans: AIDs stands for Acquired Immune Deficiency Syndrome. If a person suffers from AIDS, then they experience symptoms like fever, weakness, weight loss, etc. A syndrome refers to a set of health issues that combine to make a disease. Hence, due to the regular symptoms of certain health problems AIDS is considered to be a syndrome and not a disease. It is to be noted that various treatments have been discovered that ease the symptoms but AIDS cannot be fully cured.

6. Why are antibiotics not effective for viral diseases?

Ans: Antibiotics are medicines formed using chemicals and extracts from bacteria and fungi used to treat various illnesses.  Antibiotics treat bacterial infections by destroying the cell walls of the bacteria. Viruses do not have a cell wall which is why viral diseases cannot be treated with antibiotics. One can recover from viral diseases by building the immune system by eating healthy. The medicines help with certain symptoms but nourishing food is the main requirement in assisting the body fight the viruses responsible for the disease.

7. Why do we fall ill (Chapter 13 of Class 9 Science, Important question)?

Ans: We often suffer from acute diseases like the common cold and so on owing to the attacks of viruses or bacteria, lack of public health services, and inadequate nourishment. It is essential to look after ourselves and take preventive measures to avoid falling sick. Medicinal science has grown to provide us with various vaccines for deadly diseases while other common diseases can be treated with medicines and healthy food and sanitary habits.