NCERT Exemplar Solutions Class 9 Science Why Do We Fall III

Multiple Choice Questions (MCQs)...........

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

(a) Dengue                         

(b) AIDS                   

(c) Typhoid             

(d) Influenza

Solution 1:   (c) Typhoid. 

Typhoid is another name for typhoid fever. It's a widespread bacterial disease spread across the world that's spread by ingesting food or water contaminated with an infected person's faeces.
Breakbone fever is another name for dengue fever. The dengue virus causes a tropical disease spread by mosquitos. Fever, fatigue, muscle and joint pains, and a rash that looks like measles are among the symptoms.
Infection with the Human Immunodeficiency Virus (HIV/AIDS) causes a disease of the human immune system known as acquired immunodeficiency syndrome (HIV/AIDS) (HIV).
Influenza, also known as "the flu," is an infectious disease caused by RNA viruses that affects mammals. Chills, fever, runny nose, sore throat, muscle pains, headache (often severe), coughing, exhaustion, fatigue, and general discomfort are the most common symptoms.

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

(a) Cholera                  

(b) Tuberculosis                   

(c) Anthrax                    

(d) Influenza

Solution 2:  (d) Influenza. 

Myxovirus influenza is a virus that causes influenza.

The bacterium Vibrio cholera causes cholera, which is an infection of the small intestine. Watery diarrhea and vomiting are the most common cholera symptoms. This can lead to dehydration and, in the worst-case scenario, grayish-blue skin.
Tuberculosis is a disease caused by Mycobacterium tuberculosis, a type of bacteria. Tuberculosis is a disease that primarily affects the lungs, but it can also spread to other parts of the body. People who have the infection cough, sneeze, and transmit respiratory fluids through the air, which spreads the virus.

The bacterium Bacillus anthracis causes anthrax, which is an acute illness. The disease is fatal in most cases, and it affects both humans and animals. Anthrax vaccinations are now available, and certain strains of the disease react well to antibiotic treatment for influenza, according to Q. 1. 

Question 3:  Which one of the following disease is not transmitted by mosquito?

(a) Brain fever                                       

(b) Malaria

(c) Typhoid                                            

(d) Dengue

Solution 3:  (c) Typhoid.

Salmonella typhi is the bacteria that cause typhoid. It is a mosquito-borne disease that is spread through food and water.

Brain fever, malaria, and dengue fever are all contagious diseases spread by mosquitoes. Anopheles mosquitoes transmit malaria, Cu/ex mosquitoes transmit filariasis, and Aedes mosquitoes transmit dengue fever.

Question 4: Which one of the following disease is not caused by bacteria?

(a) Typhoid                                               

(b) Anthrax

(c) Tuberculosis                                        

(d) Malaria

Solution 4:  (d) Malaria. 

Malaria is a mosquito-borne infection caused by Plasmodium falciparum (a protozoan).

Shivering attacks occur on a regular basis, accompanied by a high fever, headache, and muscular pains. Other signs and symptoms include anemia and an enlarged spleen.

Question 5: Which one of the following disease is caused by protozoans?

(a) Malaria                                              

(b) Influenza

(c) AIDS                                                    

(d) Cholera

Solution 5:  (a) Malaria. 

Plasmodium, a protozoan, causes malaria. The RNA virus causes influenza, HIV causes AIDS, and the bacterium Vibrio cholera causes cholera.

Question 6:  Which of the following has long term effect on the health of an individual?

(a) Common cold                                       

(b) Chickenpox

(c) Chewing tobacco                                  

(d) Stress

Solution 6:  (c) Chewing tobacco. 

Chewing tobacco can have long-term consequences for a person. It raises the risk of leukoplakia, a condition that can lead to oral cancer. Tobacco chewing has been linked to cancer, particularly of the mouth and throat.

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

Solution 7:  (c) Sneezing. 

Microbes are transmitted by the tiny droplets sneezed out by an infected human. Inhaling these disease-causing microbes from a close proximity to an infected person can cause infection.

Question 8:  AIDS cannot be transmitted by

(a) sexual contact                                    

(b) hugs

(c) breast feeding                                    

(d) blood transfusion

Solution 8:   (b) hugs. 

The human immunodeficiency virus, or HIV, causes acquired immunodeficiency syndrome (AIDS). HIV gradually degrades the human immune system's effectiveness, i.e., it weakens the body's ability to fight disease. This exposes the body to other life-threatening diseases, which eventually lead to death. The modes of transmission of the AIDS virus are shown in options (a), (c), and (d).
HIV is spread through the blood, sperm, and breast milk. By transfusion of infected blood, sharing a needle with an infected person, or having sexual contact with an infected person, a person may become infected with HIV. A mother's infection can infect an unborn child, or a mother's milk can infect an infant.
Swollen lymph glands, weight loss, recurrent fever, night sweats, and diarrhoea are all common AIDS symptoms. The disorder can affect the central nervous system, causing memory loss and speech difficulties.

A cure for AIDS has not yet to be discovered. A patient is normally given a cocktail of medications to help slow down the disease's progression.
We should follow the safe practices listed below to avoid contracting HIV:

i)        We should ensure that any blood used in transfusions for our family members or ourselves has been HIV-tested. Potential blood donors should be tested for HIV by blood banks and hospitals.

ii)       Only use disposable needles and syringes.

iii)     Shaving blades and razors should not be shared.

iv)     Having multiple sex partners is not a good idea. Condoms can be used to keep HIV from spreading through sexual fluids.

Question 9:  Making anti-viral drugs is more difficult than making anti-bacterial medicines because

(i)   viruses make use of host machinery
(ii)  viruses are on the border line of living and non-living
(iii) viruses have very few biochemical mechanisms of their own
(iv)  viruses have a protein coat

Solution 9:   (i) viruses make use of host machinery.

Since viruses multiply in the host's cell, developing a safe and efficient antiviral drug is challenging. As a result, pinpointing the precise targets where the drug can interfere with the virus without harming the host organism is challenging.

Question 10:  Which one of the following causes kala-azar?

(a) Ascaris                                                  

(b) Trypanosoma

(c) Leishmania                                          

(d) Bacteria

Solution 10:  (c) Leishmania. 

Fever, weight loss, weakness, anemia, and swelling of the liver and spleen are all signs and symptoms of Leishmania, protozoa that causes kala-azar or black fever.

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) Air borne diseases                           

(d) Cholera

Solution 11:   (c) Air borne diseases. 

The nuclei of the droplets recirculate in enclosed spaces, posing a threat to everyone. As a result, overcrowding and inadequate ventilation are significant contributors to the spread of airborne diseases.

Question 12:  Which disease is not transmitted by mosquitoes?

(a) Dengue                                                  

(b) Malaria

(c) Brain fever or encephalitis                

(d) Pneumonia

Solution 12:  (d) Pneumonia. 

Pneumonia is a lung inflammatory disease that affects the alveoli. A virus or bacteria is to blame. Cough, chest pain, fever, and trouble breathing are all symptoms. Dengue, measles, and brain fever are vector (mosquito) transmitted diseases, while pneumonia is an airborne disease.

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

Solution 13:   (a) Living in clean space. 

Clean surroundings are important for good health, as is

(i) The availability of clean drinking water.

(ii) Access to safe, sufficient, and nutritious food.

(iii) Social peace and equity.

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 in not caused by staphylococci

Solution 14:  (d) Acne in not caused by staphylococci. 

Acne is a chronic human skin condition marked by seborrheic dermatitis and pimples.

Acne is caused by the anaerobic bacterium Propionibacterium acnes. Staphylococci are not the cause.

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

Solution 15:   (b) are vectors for many diseases.

Many of the animals that live with us are carriers of disease. These animals act as vectors, transferring infectious agents from a sick person to another potential host (a healthy person). Mosquitoes have been linked to a variety of diseases.

Question 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 of the above

Solution 16:   (c) it creates immunity in the body. 

Vaccines are given to children to help them develop immunity to a specific disease; they contain an agent that looks like a disease-causing microorganism and are produced from weakened or destroyed microbes.
The pulse polio programme is a polio immunisation campaign. Polio is a muscle and nerve disorder that can result in paralysis. Oral vaccines are provided to all children under the age of five in our country on a regular basis to prevent this disease.

Question 17:  Viruses, which cause Hepatitis, are not transmitted through

(a) air                       

(b) Water                   

(c) Food                    

(d) Personal contact

Solution 17:  (a) air. 

Hepatitis is a condition that causes the liver to swell. The disorder is characterised by a yellowing of the skin and the whites of the eyes, a condition known as jaundice. The presence of so much bilirubin (a bile pigment) in the blood causes the yellowing.
Viral hepatitis is caused by various strains of the hepatitis virus, which is named after the hepatitis it causes. As a result, we have hepatitis. Hepatitis strains A, B, C, D, E, F, and G are designated by the letters A, B, C, D, E, F, and G. Some of these strains (for example, hepatitis-A) are spread by contaminated food or water. Other diseases, such as hepatitis B, are spread through blood, sperm, saliva, and breast milk.

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

Solution 18:   (a) animals carry the infecting agents from sick person to another healthy person.

Vectors, also known as intermediaries, are animals or insects that bring infectious agents from one individual to another. Mosquitoes (malaria, filariasis, yellow fever, and dengue), flies (typhoid, kala-azar, and sleeping sickness), louse (typhus) and rats (for plague).

Short Answer Type Questions..................

Question 19:  Give two examples for each of the following.

(a) Acute disease                                    

(b) Chronic diseases

(c) Infectious diseases                           

(d) Non-infectious diseases

Solution 19:  

a)      Acute diseases, such as colds and coughs, last for a brief time and have no long-term consequences.

b)      Chronic diseases are those that last a long time, if not a lifetime, and have long-term consequences for human health. Tuberculosis and arthritis, for example.

c)       Infectious diseases are caused by pathogens and can be transmitted from person to person. Malaria and chickenpox, for example.

d)      Non-infectious diseases are not spread and are caused by causes other than living pathogens. Diabetes and goitre, for example.

Question 20:  Name two diseases caused by protozoans. What are their causal organisms?

Solution 20:   Malaria, which is caused by the protozoan Plasmodium, is one of two diseases caused by protozoans. Entamoeba histolytica causes amoebic dysentery.

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

Solution 21:   Helicobacter pylori, formerly known as Compylobacter pylori, are a Gram-negative bacteria found in the stomach that causes peptic ulcers. Australian scientists Barry Marshall and Reborn Warren discovered it in 1982.

Question 22:  What is an antibiotic? Give two examples.

Solution 22:   Antibiotics are medications that are used to treat diseases caused by bacteria. Antibiotics target various processes and structures in bacteria in order to destroy or stop them from growing.
The first form of antibiotic inhibits the development of a compound required for bacterial cell wall growth. This prevents the cell wall from spreading as the rest of the cell expands. Penicillin, an essential antibiotic, acts in this way for streptococcal infections by causing the cell to burst, killing the bacteria.
Some antibiotics, such as streptomycin for tuberculosis, function by interfering with other processes such as protein production.

Question 23:  Fill in the blanks.
(a) Pneumonia is an example of ________
(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________

Solution 23:

(a) Pneumonia is an example of Infectious disease.
(b) Many skin diseases are caused by fungi.
(c) Antibiotics commonly block biochemical pathways important for the growth of cell wall.
(d) Living organisms carrying the infecting agents from one person to another are called vectors.

Question 24:  Name the target organs for the following diseases
(a) Hepatitis targets ________
(b) Fits or unconsciousness targets ________
(c) Pneumonia targets ________
(d) Fungal disease targets ________

Solution 24:
(a) Hepatitis targets liver.
(b) Fits or seizure targets brain.
      It is caused by a disruption of brain electrical activity, which can be caused by disorders like epilepsy. The patient may lose consciousness or encounter conclusions in severe cases.
(c) Pneumonia targets lungs.
(d) Fungal disease targets skin.

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

Solution 25:   A 'vaccine' is a biological preparation that boosts resistance to a specific disease. Vaccines may be either prophylactic or therapeutic in nature.

Edward Jenner (1749-1823), an English physician, noticed that people who had cowpox (a mild disease) did not get smallpox (a more severe disease). Jenner wanted to put his theories about cowpox and smallpox to the test.
He used a sterile needle to extract pus from an infected girl's cowpox rashes and inject it into wounds on an uninfected boy's skin, resulting in cowpox. Jenner injected fluid from the spots of a smallpox victim into the boy's arm after he recovered. Jenner's experiment was successful because the body did not contract smallpox.
Jenner created the first smallpox vaccine using microbes from cowpox, a disease that is similar but less serious. Vaccination is derived from the Latin words vacca, which means cow, and vaccinia, which means cowpox.

Louis Pasteur, who invented vaccines for chicken pox, cholera, and anthrax, initiated the second wave of vaccines in the 1880s.

Question 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 _________
(e) Many skin diseases are caused by ______

Solution 26:

a)      Chronic disease continues for many days and causes long term effects on the body.

e.g., include elephantiasis, cardiovascular diseases, tuberculosis, diabetes, arthritis cancer etc.

b)      Acute diseases continue for a few days and causes no longer term effect on body.

e.g., Induce cold, cough, typhoid, cholera, etc.

c)       Health is defined as physical, mental and social well-being and comfort.
Being healthy means one feels good physically, has positive outlook and is able to cope with the social and mental pressures without much difficulty.

d)      Common cold is infectious disease.

e)      Many skin diseases are caused by fungi. 

e.g., Athlete’s foots ringworm etc.

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

Solution 27:
Difference between infectious and non-infectious disease are:

Question 28:  Name any two groups of microorganisms from which antibiotics could be extracted.

Solution 28:   Fungi (Penicillium notatum) and Bacteria (Streptomyces cerevisae). (Also, take a look at Q. 22).

Question 29:  Name any three disease transmitted through vectors.

Solution 29:   Disease caused by vectors is (Also, refer to Q. 18)

Long Answer Type Questions............................

Question 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.

Solution 30:

a)      The first and most important prerequisite for good health is a well-balanced diet. A well-balanced diet provides the body with all of the nutrients it requires, such as proteins, carbohydrates, fats, vitamins, and minerals, in the proper proportions. When one or more of these nutrients are missing from our diet, we develop deficiency diseases or nutritional disorders.
Obesity, Kwashiorkor, and rickets are all caused by an excess or insufficient intake of food and nutrients. If we don't get enough iron in our diet, we may develop anaemia.
Vitamin A hypervitaminosis-A and calcium rickets are caused by an abnormal intake of nutrients and minerals. Deficiency diseases are avoided by eating a well-balanced diet. It also improves our ability to combat infections more broadly.

b)      Our health depends on the cleanliness of our surroundings. Flies and mosquitoes carry germs that cause diseases, Flies breed in rotting garbage and mosquitoes breed in pools of stagnant water.
As a result, people become ill often if their living or working environment contains unclean garbage, stagnant water, or open drains. Clean air is also a part of our environment and an essential component of good health.

c)       Mosquitoes favor stagnant water because it provides a breeding site for them. Malaria, dengue fever, elephantiasis, chikungunya, and other diseases are spread by mosquitos. Our surroundings should be free of stagnant water to prevent the spread of these diseases.

d)      Humans live in communities. As a result, our social climate has a major impact on our personal wellbeing. Our physical environment is determined by our social environment, whether we live in villages, towns, or cities.
For example, if there is no agency to ensure that garbage is collected and disposed of, and no one takes responsibility for cleaning the drains, no one takes responsibility for ensuring that waste water does not get collected in the streets or open spaces, there will be heaps of garbage and trash scattered here and there, and there will be stagnant open drain water around where we live.
As a result, the likelihood of bad health will rise. As a result, public sanitation makes a significant contribution to an individual's health.

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

Solution 31:   Physiological malfunctions, psychological factors, and pathogenic species all have a negative impact on human health. The word "disease" refers to a state of being unable to relax or enjoy oneself. Disease is characterised as a disruption (malfunctioning) of a living organism's normal state that disrupts or modifies the output of vital organs and impairs their function. Disease can be caused by a variety of factors, including:

i)        Environmental factors (as malnutrition, industrial hazards or climate).

ii)       Specific infectious agents (as worms, protozoans, fungi, bacteria or viruses).

iii)     The organism's inherent flaws (as genetic anomalies).

iv)     A combination of the above variables.

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

Solution 32:  Symptoms are noticeable changes in our body or some of its components that indicate the existence of a disease. They may take the form of structural or functional changes. Doctors look for definite signs or sings for a specific disease based on these symptoms. For example, the symptoms for malaria and typhoid are similar, such as fever, fatigue, and headache. However, the symptoms of the disease vary, as malaria fever is characterised by chills, while typhoid fever is characterised by rashes, stomach pain, and other symptoms.

Malaria can be detected with a simple blood test (CBC), whereas typhoid requires a widal test.

Question 33:  Why is immune system essential for our health?

Solution 33:   Lymphoid glands, tissue cells, and antibodies make up the human immune system. Foreign antigens are recognised by the immune system, which triggers an immune response and remembers them.

The way the human body reacts to the invasion of particular pathogens or antigens is called an immune response. These responses involve the production of cells (lymphocytes) and chemicals (antibodies) that are designed to defend the body against the pathogens. Antigens are substances that can activate an immune response. Antigens cause the immune system to produce antibodies (glycoproteins or immunoglobulins). Each form of antibody recognizes a specific antigen and reacts with it to neutralize it.

Question 34:  What precautions will you take to justify “prevention is better than cure”?

Solution 34:   When a person contracts a disease:

i)        His or her body functions are harmed, and he or she can never fully recover.

ii)       At some stage, he or she may become bedridden.

iii)     He or she can act as a vehicle for disease transmission, so prevention is preferable to cure.

Ways to Combat Infectious Diseases, Public Hygiene is the Secret to Infectious Disease Prevention. The following general practices are used to avoid diseases:

i)        Limit your exposure to bacteria in the air.

ii)       Adopting non-overcrowding living conditions.

iii)     Avoid contact with waterborne microbes.

iv)     Drinking water that is safe to drink should be available.

v)      Avoid vector-borne disease and provide a safe environment to prevent mosquito breeding.

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

Solution 35:   Due to their poor immunity, or slow immune response, some children become ill more frequently than other children in the same region.

Question 36:  Why are antibiotics not effective for viral disease?

Solution 36:  Antibiotics are ineffective against viral diseases since the virus grows and divides using the machinery of the host organism. As a result, aiming the virus without affecting the host becomes difficult.

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

Solution 37:  Microbes are usually fought by a healthy person's powerful immune system. Pathogenic microbes are killed by specialised cells in the body. When infectious microbes invade the body, these cells become active, and if they are effective in eliminating the pathogen, we remain disease-free.

As a result, a person with a strong immune system may not get sick even though they are exposed to infectious microbes.

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

Solution 38:   There are four factors that must be present in order for an individual to be healthy:

i)        Consumption of a well-balanced diet

ii)       A safe and healthy community

iii)     Social cohesion

iv)     Favorable economic circumstances

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

Solution 39:   AIDS stands for Acquired Immune Deficiency Syndrome. The Human Immunodeficiency Virus, or HIV, is to blame. It is possible to be infected with HIV but not develop AIDS. It is classified as a syndrome rather than a disorder since it is characterised by a group of health problems. As a result of AIDS, people are more vulnerable to bacterial, infectious, fungal, and parasitic infections. Individuals may have higher rates of cancers such as lymphomas.

A syndrome is technically classified as a group of symptoms that are common to a disorder or disease (but it may be due to multiple diseases or no disease, e.g., an accident). A disease, on the other hand, is a disorder of a specific organ or body system caused by heredity, infection, or environmental factors, among other things.