NCERT Exemplar Class 9 Science Solutions Chapter 13 Why do we fall ill?

Access to NCERT Exemplar Class 9 Science Solutions Chapter 13-MCQ

Question:1

Which one of the following is not a viral disease?
(a) Dengue
(b) AIDS
(c) Typhoid
(d) Influenza
Answer:The correct answer is option(c), Typhoid

Explanation: Typhoid is not a viral disease as it is caused by bacteria called Salmonella typhi, not by a virus. Apart from this dengue, AIDS and influenza are viral diseases and caused by different types of virus.

Question:2

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

Answer: The correct answer is option(d), Influenza

Question:3

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

Answer: The correct answer is option(c), Typhoid.

Explanation: Typhoid is caused by the bacteria Salmonella typhi. It is not transmitted by mosquitoes but rather through contaminated food and water. The other three are caused by mosquitoes, Culex or anopheles.

Question:4

Which one of the following diseases is not caused by bacteria?
(a) Typhoid
(b) Anthrax
(c) Tuberculosis
(d) Malaria

Answer: The correct answer is option(d), Malaria.

Explanation: Malaria is caused by plasmodium parasites transmitted by females anopheles mosquito thus, it is not a bacterial disease, but a parasitic disease. All the other three are bacterial diseases.

Question:5

Which one of the following diseases is caused by protozoans?
(a) Malaria
(b) Influenza
(c) AIDS
(d) Cholera

Answer: The correct answer is option (a), Malaria.

Question: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

Answer: The correct answer is option(c), chewing tobacco.

Explanation: Chewing tobacco has the most significant long-term effects on individual health.

Question: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

Answer: The correct answer is option(c), sneezing

Explanation: Sneezing releases microbes into the air, and coming into contact with an infected person who is sneezing can transfer the illness and make a normal human sick. All other three are non-communicable diseases.

Question:8

AIDS cannot be transmitted by
(a) sexual contact
(b) hugs
(c) breastfeeding
(d) blood transfusion

Answer: The correct answer is option (b), Hugs

Explanation: AIDS is caused by the Human Immunodeficiency Virus (HIV) and is transmitted by sexual contact and blood-to-blood contact with an infected person; hence, hugs cannot transmit this disease.

Question: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 borderline of living and non-living
(c) viruses have very few biochemical mechanisms of their own
(d) viruses have a protein coat

Answer: The correct answer is option (c): Viruses have very few biochemical mechanisms of their own

Explanation: In the case of viral diseases, the virus uses the cells of the infected person as the host and uses their biochemical mechanisms to survive and divide, as the viruses have very few biochemical mechanisms of their own. Antiviral drugs are difficult to make as the drug needs to be extremely specific in destroying the viruses causing the disease without affecting or killing a significant number of the human body’s cells.

Question:10

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

Answer: The correct answer is option(c), Leishmania

Explanation: Leishmania is a parasitic protozoan that causes the disease Kala-azar. This disease is transmitted by the bite of infected female sandflies.

Question: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) Airborne diseases
(d) Cholera

Answer: The correct answer is option(c), Airborne diseases

Explanation: Airborne diseases like tuberculosis and influenza spread easily in crowded and poorly ventilated houses, as respiratory droplets remain in the air and cause illness in a normal person.

Question:12

Which disease is not transmitted by mosquitoes?
(a) Dengue
(b) Malaria
(c) Brain fever or encephalitis
(d) Pneumonia

Answer: The correct answer is option(d), Pneumonia

Explanation: Pneumonia is spread through the air and is caused by bacteria, viruses, or fungi. This disease affects the lungs of an infected person. All other three are caused by mosquitoes.

Question: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

Answer: The correct answer is option(d), living in a large and well-furnished house.

Explanation: Living in a large and well-furnished house may provide comfort, but it is not essential for maintaining individual health. Cleanliness, economic stability, and social harmony are more important to maintaining health.

Question: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

Answer: The correct answer is option(c): Peptic ulcers are caused by eating acidic food.

Explanation: Peptic ulcers are mainly caused by Helicobacter pylori bacteria, which leads to stomach infection. Acidic foods may irritate an existing ulcer but do not cause them. So the c statement is the wrong one.

Question: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

Answer: The correct answer is option(b), which are vectors for many diseases.

Explanation: Mosquitoes cause many diseases such as malaria, dengue, chikungunya, etc., and hence mosquitoes are not allowed to breed in our surroundings as they are vectors for many diseases.

Question:16

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

Answer: The correct answer is option(b), Water

Explanation: Hepatitis are of five main types, namely A, B, C, D, and E. Out of them, Hepatitis A is very common in India. The most common cause of Hepatitis transmission is contaminated water.

Question:17

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

Answer: The correct answer is option(a), animals carrying the infecting agents from a sick person to another healthy person.

Explanation: Vectors are the infectious agents, such as viruses, bacteria, protozoans, etc, that carry the infectious agents from a sick person to a healthy one.

Explore the Short Answers of NCERT Exemplar Class 9 Science Solutions Chapter 13

Question:1

Give two examples for each of the following
(a) Acute diseases
(b) Chronic diseases
(c) Infectious diseases
(d) Non-infectious diseases

Answer: Two examples for each of the following are:-

1. Acute diseases: Viral fever and Flu

2. Chronic diseases: Elephantiasis and Tuberculosis

3. Infectious diseases: Chicken Pox and HIV/Aids

4. Non-infectious diseases: Cancer and Diabetes

Question:2

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

Answer: Two diseases caused by Protozoans are:

1. Kala-azar is caused by Leishmania, which is a prozoan parasite.

2. Sleeping sickness is caused by the organism Trypanosoma brucei.

Question:3

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

Answer: Helicobacter pylori, which is a spiral-shaped bacterium, causes peptic ulcers.

This pathogen was discovered by two Australian researchers, Barry J. Marshall and Robin Warren in the year 1982. Both of the researchers have been awarded the Nobel Prize in Medicine in the year 2005.

Question:4

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 is called ———.
Answer:

1. Pneumonia is an example of Bacterial disease.

2. Many skin diseases are caused by Fungi

3. Antibiotics commonly block biochemical pathways important for the growth of Bacteria.

4. Living organisms carrying the infecting agents from one person to another is called Vectors.

Question:5

Name the target organs for the following diseases
(a) Hepatitis targets———.
(b) Fits or unconsciousness targets ———.
(c) Pneumonia targets ———.
(d) Fungal disease targets ———.
Answer:

1. Hepatitis targets Liver.
2. Fits or unconsciousness targets Brain.
3. Pneumonia targets Lungs.
4. Fungal disease targets Skin.

Question:6

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

Answer: Vaccine was discovered by Edward Jenner in the year 1796. This vaccine was developed for smallpox and turned out to be the first successful vaccine in the world.
Two diseases which can be prevented by using vaccines:

1. Smallpox

2. Polio

Question:7

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———.
Answer:

1. Chronic disease continues for many days and causes long term effect on body

2. Acute disease continues for a few days and causes no longer-term effect on body.

3. Health is defined as physical, mental and social well-being and comfort.

4. Common cold is viral disease.

5. Many skin diseases are caused by fungi.

Question:8

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
Answer:

Question:9

Name any two groups of micro-organisms from which antibiotics could be extracted.
Answer: Two groups of micro-organisms from which antibiotics could be extracted are:

1. Bacteria: An Example of the same is the Streptomyces species.

2. Fungi: An Example of the same is Penicillium notatum.

Question:10

Name any three diseases transmitted through vectors
Answer: The animals that carry infectious agents such as viruses, bacteria, protozoans, etc., from an infected person to a healthy host are termed vectors. The most common example for Vectors is mosquitoes which cause many diseases such as Malaria, Dengue fever etc.

Three diseases transmitted through vectors are:

1. Brain Fever is also known as Encephalitis, which is transmitted by mosquitoes of the Culex species.

2. Malaria is transmitted by Anopheles Mosquitoes.

3. Dengue fever is transmitted by Aedes Mosquitoes.

Unlock the Long Answer Questions of Why do we Fall ill? NCERT Exemplar Class 9 Science Solutions Chapter 13

Question:1

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.
Answer:

(a) A balanced diet is essential for maintaining a healthy body because it provides all the important nutrients, vitamins, and minerals that are required for the proper functioning of the body. It includes the correct amount of carbohydrates, proteins, fats, vitamins, and minerals, ensuring that the body receives enough energy and nutrients. Deficiency of nutrients that lead to various diseases in the body such as anemia, heart diseases etc. are also prevented by taking a balanced diet.

(b) The health of an organism depends on the surrounding environmental conditions because the environment affects the presence of clean air, water, food, and shelter, all of which are essential for survival. A clean environment reduces the risk of respiratory problems and other diseases, such as cholera and typhoid. Poor environmental conditions, such as air and water pollution and overcrowding, can lead to the spread of diseases and harm physical and mental health. Therefore, maintaining a clean and safe environment is important for the overall health of all living organisms.

(c) Our surrounding area should be free of stagnant water because stagnant water provides an area for mosquitoes to reproduce, which cause dangerous diseases such as malaria, dengue, etc. and aslo lead to water borne diseases like cholera and typhoid. It produces foul odors and contributes to environmental pollution. By preventing the accumulation of stagnant water, we can reduce the risk of disease, maintain cleanliness, and promote a healthy environment.

(d) Social harmony and good economic conditions are essential for maintaining good health because they create an environment where individuals can survive physically, mentally, and emotionally. Social harmony promotes peaceful existence, reducing stress and anxiety and encouraging positive mental health. On the other hand, good economic conditions allow easy access to resources such as food, clean water, quality healthcare, and education.

Question:2

What is a disease? How many types of diseases have you studied? Give examples
Answer: A disease is a condition that affects the normal functioning of the body or mind. These changes worsen the state of a healthy body, and these can be caused by pathogens, genetic factors, or unhealthy lifestyle choices.

The four types of diseases studied are mentioned below:

1: Acute Diseases - The diseases that develop suddenly and last for a short period are known as acute diseases. Examples- Viral fever and Flu.

2: Chronic diseases - These diseases develop slowly and last for a longer period, often for months or years. Examples- Diabetes and Asthma.

3: Infectious diseases- These diseases are caused by pathogens such as bacteria, viruses, and fungi and can spread from person to person. Examples- Tuberculosis and Malaria

4: Non-infectious diseases- The diseases that are not caused by pathogens and do not spread from person to person are known as non-infectious diseases. Examples- Cancer and diabetes.

Question:3

What do you mean by disease symptoms? Explain giving two examples?
Answer: A symptom is an indication of a disease or health condition that is experienced and reported by the patient. Every disease showcases its signs and symptoms that cannot be measured or observed directly by others but are felt by the individual.

Examples:

1. Fever in Malaria - The common symptoms are high fever, chills, and sweating.

2. COVID–19 - The most common symptoms of this are fever, tiredness, and headache.

Symptoms help doctors identify diseases and provide suitable treatments.

Question:4

Why is immune system essential for our health?
Answer: The immune system is important for maintaining our health because it protects the body from harmful pathogens such as bacteria, viruses, and fungi. It acts as the body's defense mechanism, identifying and removing harmful pathogens that can cause diseases.

The absence of or a poor immune system can leave an individual’s body unprotected against the harmful substances that enter inside or affect our system.
Key Functions of the Immune System:

1-The immune system recognizes harmful microbes and kills them before they can cause harm. Example: Fighting from the viruses like influenza or bacteria causing pneumonia.

2. It eliminates infected or abnormal cells to prevent the spread of infection.

3. The immune system recognizes and removes damaged or cancerous cells, preventing the development of tumors.

4. After a pathogen enters our body, the immune system "remembers" it, which provides quicker and stronger responses in the future.

Question:5

What precautions will you take to justify “prevention is better than cure”.
Answer: Taking preventive measures helps in reducing the risk of developing diseases. Below are some important precautions that go with the principle that prevention is better than cure:

1. Regular handwash with soap kills germs and prevents the spread of infections.

2. Vaccines help the body build immunity against diseases. Example: Vaccines for polio, measles.

3. A balanced diet and consuming nutritious food strengthen the immune system and improve overall health.

4. Drinking clean water and having good sanitation prevent waterborne diseases.

5. Doing physical activity and exercise keeps the body fit and reduces stress.

6. Pollution should be reduced to have a clean environment.

By following these precautions, human beings can reduce diseases and live a healthy lifestyle.

Question:6

Why do some children fall ill more frequently than others living in the same locality?
Answer: Children living in the same locality may have different frequencies of illness due to various factors, which are explained below:

• Some children have a weaker immune system, making them more sensitive to infections and illnesses.

• A lack of essential nutrients makes the defense system of the body weak, thus increasing the chances of diseases.

• Children who miss or delay vaccinations are at a higher risk of getting ill.

• Poor personal hygiene leads to an increase in the chances of the children falling ill.

Question:7

Why are antibiotics not effective for viral disease?
Answer: Antibiotics are made to target and kill bacteria by stopping their growth, reproduction, and metabolism. However, they are not effective against viral diseases because viruses and bacteria are different in structure and function. Viruses are non-cellular organisms that are enclosed in a protein coat. Since viruses do not have a cell wall or cell membrane, antibiotics have no target to attack, and viruses invade and replicate inside the host’s cells and antibiotics cannot penetrate them.

Question:8

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

Answer: Not everyone who is infected by an infectious microbe develops a noticeable disease. The most common example of this is COVID-19. Several factors determine whether an infection will result in a disease, which are :

• A healthy immune system can recognize and eliminate harmful microbes before they multiply and cause harm in the body of a human being.

• Some microbes have a low ability to cause disease, which means they may not produce acute symptoms even if they enter the body.

• If the number of microbes entering the body is too low, the immune system can kill them before they cause any damage.

• If a person has been vaccinated, their immune system may recognize and destroy the microbe before it can cause any illness.

Question:9

Give any four factors necessary for a healthy person.
Answer: Four Factors Necessary for a Healthy Person are given below:

1. Balanced Diet - Having a diet that is rich in important nutrients gives the body energy and increases overall growth and immunity.

2. Regular Exercise- Doing daily exercise and physical activity improves health, strengthens muscles, and boosts our immunity.

3. Personal Hygiene - A person needs to take care of their personal hygiene and its surroundings because it reduces the risk of infections and diseases.

4. Mental and Emotional Well-being- A Person having good mental health, reduce its stress, and contributing to overall well-being and health.

Question:10

Why is AIDS considered to be a ‘Syndrome’ and not a disease?
Answer: AIDS (Acquired Immunodeficiency Syndrome) is considered a syndrome rather than a disease because it is a collection of symptoms and infections that result from the excess weakening of the immune system, which is caused by HIV.

There are multiple reasons for this, which are:-

• AIDS affects various systems such as the immune, respiratory, digestive, and nervous, therefore, it is classified as a syndrome.

• AIDS is the final stage of HIV infection, where the immune system is damaged, making the body easily affected by infections.

• AIDS cannot be considered a single condition but presents a combination of symptoms and disorders because it affects multiple organs.