NCERT Exemplar Class 9 Science Chapter 13 Why do we Fall ill are part of NCERT Exemplar Class 9 Science. Here we have given NCERT Exemplar Class 9 Science Solutions Chapter 13 Why do we Fall ill.

NCERT Exemplar Class 9 Science Solutions Chapter 13 Why do we Fall ill
Multiple Choice Questions

Question 1.
Which one of the following is not a viral disease?
(a) Dengue
(b) AIDS
(c) Typhoid
(d) Influenza
Solution:
(c) Typhoid is a bacterial disease caused by Salmonella typhi. Dengue, AIDS and influenza are viral diseases respectively caused by flavi-ribo virus, human immunodeficiency virus (HIV) and orthomyxovirus.

Question 2.
Which one of the following is not a bacterial disease?
(a) Cholera
(b) Tuberculosis
(c) Anthrax
(d) Influenza
Solution:
(d) Influenza is a viral disease caused by orthomyxovirus whereas cholera, tuberculosis and anthrax are bacterial diseases respectively caused by Vibrio cholerae, Mycobacterium tuberculosis and Bacillus anthracis.

Question 3.
Which one of the following disease is not transmitted by mosquito?
(a) Brain fever
(b) Malaria
(c) Typhoid
(d) Dengue
Solution:
(c) Typhoid is a bacterial disease caused by Salmonella typhi. It is a vehicle borne disease which is transmitted by contaminated food and water. Brain fever (Japanese encephalitis), Malaria and dengue are transmitted by Culex, female Anopheles and Aedes mosquitoes respectively

Question 4.
Which one of the following disease is caused by bacteria?
(a) Typhoid
(b) Anthrax
(c) Tuberculosis
(d) Malaria
Solution:
(a), (b) and (c) Typhoid, anthrax and tuberculosis are all bacterial diseases caused by Salmonella typhi, Bacillus anthracis and Mycobacterium tuberculosis respectively. Malaria is a protozoan disease, caused by Plasmodium and is transmitted from infected individual to healthy individual by the bite of female Anopheles mosquito.

Question 5.
Which one of the following diseases is caused by protozoans?
(a) Malaria
(b) Influenza
(c) AIDS
(d) Cholera
Solution:
(a) Refer to answer

Question 6.
Which one of the following has a long term effect on the health of an individual?
(a) Common cold
(b) Chicken pox
(c) Chewing tobacco
(d) Stress
Solution:
(c) Common cold and chicken pox are acute diseases. Acute diseases are short duration diseases in which the normal activity of a person gets impaired for few days. These diseases normally do not cause long term effects on the health of an individual. Stress can be acute or chronic and accordingly it may have short term or long term effect on human body. Chewing tobacco leads to tobacco addiction i.e., physiological and psychological dependence on tobacco. It may eventually lead to serious diseases such as heart and lung diseases etc. Thus, chewing tobacco has long term effects on health of an individual.

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:
(c) By sneezing, an infected person releases droplets which carry the disease- causing microorganisms. These disease-causing microorganisms are inhaled by a healthy person when he/she comes in contact with an infected person. This can make the healthy person ill.

Question 8.
AIDS cannot be transmitted by
(a) sexual contact
(b) hugs
(c) breastfeeding
(d) blood transfusion.
Solution:
(b) AIDS is an infectious disease which spreads through sexual contact, use of contaminated needles or syringes to inject drugs or vaccines, from infected mother to child during pregnancy or breast feeding, during blood transfusion, organ transplantation, etc.
AIDS is not transmitted by shaking hands, kissing and hugging, insect bites, sharing towels, etc.

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 border line of living and non-living
(c) viruses have very few biochemical mechanisms of their own
(d) viruses have a protein coat
Solution:
(a) and (c) It is difficult to make antiviral medicines than anti-bacterial drugs. One reason is that viruses have few biochemical mechanisms of their own. They enter host’s cells and use host’s cell machinery for their life processes. This implies that there are relatively few virus-specific targets to aim at.

Question 10.
Which one of the following causes kala-azar?
(a) Ascaris
(b) Trypanosoma
(c) Leishmania
(d) Bacteria
Solution:
(c) Leishmania donovani is a parasitic protozoan that causes the disease kala-azai (dum-dum fever). The parasite is transmitted by sandfly.

Question 11.
If you live in a 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:
(c) In overcrowded and poorly ventilated condition, the air borne diseases are likely to spread rapidly. This is because infectious microbes that cause common cold, tuberculosis, pneumonia, etc. can spread through air from infected persons. The infected person throws out little droplets on sneezing, coughing or spitting. Someone standing closely can breathe in these droplets and, thus, microbes get a chance to start a new infection in this person.

Question 12.
Which disease is not transmitted by mosquitoes?
(a) Dengue
(b) Malaria
(c) Brain fever or encephalitis
(d) Pneumonia
Solution:
(d) Pneumonia is a bacterial disease caused by Streptococcus pneumoniae and Haemophilus influenzae. It is a serious disease of lungs, and is transmitted by coughing, sneezing or spitting of the diseased person. Also refer to answer 3.

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:
(d) Living in a large and well furnished house is not a necessasity for keeping good health. A person living in a small and less furnished house can also keep good health of himself if he/she maintains hygiene in his/her house and surrounding environment.

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.
Solution:
(c) Peptic ulcers are the painful sores in the lining (mucous membrane) of stomach (gastric ulcer) or«duodenum (duodenal ulcer). The symptoms include pain and bleeding in the stomach and duodenum. The peptic ulcers are caused by a bacterium Helicobacter pylori or by intake of certain drugs.

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:
(b) Vectors are living organisms that transmit infectious diseases from animals to humans or from humans to humans, without themselves being affected by the disease. Mosquitoes are the blood-sucking insects which ingest disease producing microorganisms during a blood meal from an infected host (human or animal) and later inject it into a new host during their subsequent blood meal. Mosquitoes are the vectors for a large number of diseases such as dengue, malaria, filariasis, brain fever, chikungunya, yellow fever, etc.

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 the above.
Solution:
(c)

Vaccination is a technique to develop immunity in individuals without infection.
The term vaccine is used for a preparation of antigenic proteins of pathogens or weakened or dead pathogens which on inoculation into a healthy person provides temporary/permanent immunity against the diseases by inducing antibodies formation.
The pathogens, given in a vaccine, are unable to cause a disease but are sufficient to generate the primary immune response.
Question 17.
Viruses, which cause hepatitis, are transmitted through
(a) air
(b) water
(c) food
(d) personal contact.
Solution:
(b) and (c) Hepatitis is an inflammation of liver. Hepatitis which is caused by virus is of different types such as Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D and Hepatitis E. Common modes of transmission of viruses of different types of hepatitis are intake of contaminated food or water, sexual contact with diseased person, from mother to child during pregnancy or child birth, sharing needles or syringes, blood transfusion, etc.

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:
(a) Refer to answer 15.

Short Answer Type Questions

Question 19.
Give two examples for each of the following.
(a) Acute diseases
(b) Chronic diseases
(c) Infectious diseases
(d) Non-infectious diseases Era lilt
Solution:
(a) Common cold, typhoid, chicken-pox
(b) Diabetes, tuberculosis, elephantiasis
(c) Small-pox, chicken-pox, measles
(d) Diabetes, goitre, kwashiorkor

Question 20.
Name two diseases caused by Protozoans. What are their causal organisms?
Solution:
Two diseases caused by protozoans are malaria and sleeping sickness. Causal organism of malaria is Plasmodium vivax and causal organism of sleeping sickness is Trypanosoma gambiense.

Question 21.
Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?
Solution:
Helicobacter pylori is the bacterium which causes peptic ulcers. B. Marshall and R. Warren (2005′ discovered this pathogen for the first time.

Question 22.
What is an antibiotic? Give two examples.
Solution:
Antibiotics are the chemicals secreted by microorganisms like fungi and bacteria that kill or hinder the growth of certain other kinds of microorganisms like bacteria, e.g., pen;cillin and streptomycin.

Question 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 .
Solution:
(a) infectious/communicable
(b) fungi
(c) bacteria
(d) 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:
(a) liver
(b) brain
(c) lungs
(d) skin

Question 25.
Who discovered ‘vaccine’ for the first time? Name two diseases which can be prevented by using vaccines.
Solution:
Edward Jenner (1796) discovered vaccine for the first time. Diseases which can be prevented by using vaccines are small pox, tetanus, polio, measles, hepatitis-B, tuberculosis, etc.

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 disease.
(e) Many skin diseases are caused by .
Solution:
(a) Chronic, long term effect
(b) Acute
(c) Health
(d) infectious/communicable
(e) fungi

Question 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
Solution:
Infectious diseases — AIDS, tuberculosis, cholera, pneumonia. Non-infectious diseases — High blood pressure, heart disease, cancer.

Question 28.
Name any two groups of micfo-organisms from which antibiotics could be extracted.
Solution:
Bacteria and Fungi are the two groups of microorganisms from which antibiotics could be extracted.

Question 29.
Name any three diseases transmitted through vectors.
Solution:
Three diseases transmitted by vectors are sleeping sickness (by tsetse fly), malaria (by female Anopheles mosquito) and dengue (by Aedes mosquito).

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:
(a) Balanced diet contains all the nutrients (carbohydrates, fats, vitamins, minerals, proteins) in appropriate amounts, which are required for maintaining proper health, for growth and repair, for fighting against diseases. Lack of balanced diet results in occurrence of diseases. Thus, balanced diet is necessary for maintaining healthy body.

(b) Health is a state of being well enough
to function well physically, mentally and socially and these conditions, depend upon the surrounding environmental conditions. If there are unhygienic conditions in the surrounding area such as piling of garbage, stagnant water etc. we might get infected and diseased. Thus, health of an organism depends upon the surrounding environmental conditions. ‘

(c) Stagnant water is the breeding place for a large number of disease-causing organisms and vectors. It leads to the spread of diseases in human beings. Thus, our surrounding area should be clean of stagnant water.

(d) Social harmony refers to peaceful interaction of human dynamics among members of a social group or groups. Human beings live in societies. The social environment therefore plays an important role in determining their health. Different types of localities such as villages, towns, cities, etc. determine the social and physical environment, which are to be kept in harmony to -maintain every individual’s health. Good economic conditions are also necessary to maintain good health. We need good food for healthy body and for this we need to earn more. For the prevention as well as treatment of diseases, one has to be in good economic condition so as to avail proper vaccination, good sanitary conditions, medicines, health advise, etc.

Question 31.
What is a disease? How many types of diseases have you studied? Give examples.
Solution:
Disruption in the functioning of a tissue, organ or organ system resulting in discomfort is referred to as disease.
Human diseases can be classified in different ways:
(i) Acute and chronic diseases.
(ii) Infectious and non-infectious diseases.

(i) Acute and chronic diseases
Acute diseases: These are short duration diseases in which normal activity of the person is impaired for a few days. These diseases do not have a long term effect on the affected individual. Examples—common cold, typhoid, diarrhoea, etc.
Chronic diseases: These are long duration diseases which last for a long time, even as much as a lifetime. These cause long term effects on human health. Examples— elephantiasis, diabetes, arthritis, etc.
Infectious and non-infectious diseases
Infectious (or communicable) diseases: These diseases are caused by pathogens such as bacteria, viruses, protozoans, etc. and are spread from diseased person to the healthy person by means of air, food, water, vectors, physical contact etc. Examples—tuberculosis, chicken-pox, dengue, etc.
Non-infectious (or non-communicable) diseases: These diseases remain confined to the person who develops them and do not spread to others. These may be caused by deficiency of nutrients, imbalance of hormones, malfunctioning of some organs or of immune system, etc. Examples—Epilepsy, allergy, goitre, Marasmus, etc.
Question 32.
What do you mean by disease symptoms? Explain giving two examples?
Solution:
When the functioning or the appearance of one or more systems of the body will change for the worse, it gives certain abnormal sign? of the disease. These visual changes in humr n beings are called symptoms. Symptoms give indication of the presence of a particular diseases.
Examples
(i) Cough and breathlessness are the symptoms of tuberculosis.
(ii) Swelling and infection of hver are the symptoms of jaundice.

Question 33.
Why is immune system essential for our health?
Solution:
The immune system of our body acts as a defense mechanism to fight against pathogenic microbes. It has cells that are specialised to kill infecting microbes and protect us from diseases. The immune cells manage to kill oh the infection long before it assumes major proportions. A strong immune system is thus essential to keep us healthy.

Question 34.
What precautions will you take to justify “prevention is better than cure”.
Solution:
If we prevent the entry of the disease causing pathogens into our body, then we can prevent the disease from occurring instead of curing the disease after suffering from it.
For preventing the occurrence of disease following precautions should be taken :

Take balance diet
Maintain proper hygienic conditions
Maintain proper sanitary conditions
Health education and awareness about diseases among masses
Clean air and safe drinking water
Medical checkup at regular intervals
Vaccination.
Question 35.
Why do some children fall ill more frequently than others living in the same locality?
Solution:
Frequency of falling ill depends on the strength of body’s immune system to fight against pathogenic microbes. Some children fall ill frequently due to th’ier poorly developed immune system. Adequate nutrition and exercise are required for the development of strong immune system.

Question 36.
Why are antibiotics not effective for viral disease?
Solution:
Antibiotics work by blocking the biosynthetic pathways of the pathogen such as bacteria, without affecting the diseased person. In case of viruses, they have very few biochemical pathways of their own. They use the metabolic machinery of the host and then reproduce. Thus, antibiotics cannot block any of their own biochemical pathways and are not effective for viral diseases.

Question 37.
Becoming exposed to or infected with an infectious microbe does not necessarily mean developing noticeable disease. Explain.
Solution:
Microbes of different diseases are always present in our surrounding environment and we are also prone to coming in contact with persons suffering from infectious diseases direcrtly or indirectly. But, because of strong immune system and presence of antibiodies against specific diseases we do not necessarily develop that disease.
Immune system of our body fights back the pathogens entering the body and most often successfully removes them. In this way our body remains protected from diseases. Antibodies to fight pathogens may develop in natural way or may be produced inside body through vaccination.

Question 38.
Give any four factors necessary for a healthy person.
Solution:
Four factors necessary for being healthy are:

Proper nutrition, balanced diet along with exercise are necessary for developing good immune system.
Personal hygiene helps to prevent infectious diseases.
Cleanliness of surrounding environment helps to prevent air, water and vector brone diseases.
Immunisation against diseases prevents their occurrence and spread.
Question 39.
Why is AIDS considered to be a ‘Syndrome’and not a disease?
Solution:
HIV (Human immunodeficiency virus) that causes AIDS comes into the body via., the sexual organs or any other means like blood transfusion will spread^to lymph nodes all over the body. The virus damages the immune system of the body and due to this the body can no longer fight off many minor infections. Instead, every small cold can become pneumonia, or minor gut infection can become severe diarrhoea with blood loss.

The effect of disease becomes very severe and complex, at times killing the person suffering from AIDS. Hence there is no specific disease symptoms for AIDS but it results in a complex diseases and symptoms. Therefore, it is known as a syndrome.