1. health and fitness
2. disease

13. Why Do We Fall Ill
13.1 HEALTH AND ITS FAILURE
Two Marks Questions (30 words)
1. Explain how individual health depends on social and mental well-being.
(CBSE, SA-2, 2012—47004)
Ans. Social well-being : Cleanliness around the place where we live. No garbage,
no open drawing etc.
Mental well being : For good health we have to be happy, social equality and
harmony are essential.
2. ‘Being disease free is not the same as being healthy’. Explain the above statement
giving an example.
(CBSE, SA-2, 2012—47008)
Ans. Being free from disease does not guarantee to good health. If a person is suffering
from the mental tension, he cannot be said fallen ill. Still he is unhealthy.
3. List any four essential factors that must be taken care of by an individual for
(CBSE, SA-2, 2012—47005)
keeping good health.
Ans. (i) Balance diet.
(ii) Disease free environment.
(iii) Proper sanitation.
(iv) Mental and social stability.
Three Marks Question (50 words)
4. Mention the symptoms because of which you will visit the doctor and why ?
(CBSE, SA-2, 2011—19/B1)
Ans. In headache, cough, cold, loose motions, wound with continuous pain in the
body parts, loss of body weight, breathlessness, feeling tired all the time, we visit to a
doctor because we might be suffering from some diseases.
13.2 DISEASES AND ITS CAUSES
Two Marks Questions (30 words)
1. (i) Name a worm which is found in our small intestine.
(ii) Name the bacteria which can cause acne.
(iii) Which protozoan is responsible for sleeping sickness ?
(iv) Which disease is caused by the protozoan Leishmania ?
(CBSE, SA-2, 2012—1079, 47026)
Ans.
(i) Ascaris.
(ii) Staphylococci.
(iii) Trypanosoma.
(iv) Kala-azar
2. Which disease is more harmful : Acute or chronic disease ? Why ?
(CBSE, SA-2, 2012—1004)
Or
Which amongst the two diseases : Acute or chronic has adverse effect on the health of
(CBSE, SA-2, 2012—47009)
a person ? Explain giving a suitable example.
(152)
Science – IX (Why Do We Fall Ill) / 153
Ans. Chronic disease lasts for long time so it is more harmful than acute disease.
For example : Cough and cold are acute diseases while tuberculosis is chronic and affects
health badly.
3. Differentiate between acute and chronic diseases. Write one example of each.
(CBSE, SA-2, 2012—1076, 47006, 47009, 47032; 2011—02/C1)
Ans.
(i)
(ii)
(iii)
(iv)
4. Why are
Acute disease
Chronic disease
These diseases last for only a
(i) These diseases last for a long
short period of time
period.
It is caused randomly.
(ii) It is caused in due course of time.
It does not cause major effect
(iii) It causes major effect on general
on general health.
health.
Example : Cough.
(iv) Example : Elephantiasis.
we advised to take blend and nourishing food when we are sick ?
(CBSE, SA-2, 2012—1004; 2011—06/B1)
Ans. We are advised to take blend and nourishing food so that scarcity (loss) of
nutrients caused during sickness may be fulfilled.
Three Marks Questions (50 words)
5. (i) Define ‘disease’.
(ii) Explain briefly the two groups of causes of diseases. (CBSE, SA-2, 2011—33/A1)
Ans. (i) Disease : When the functioning or the appearance of one or more systems
of the body changes for the worse then the body is said to be suffering from some diseases.
(ii) The two causes of diseases are : (a) Infectious causes, (b) Non-infectious causes
(a) Infectious causes : Diseases where microbes are the immediate cause are called
infectious disease.They spread in the community by microbes.
(b) Non-infectious causes : They do not spread in the community. Instead these
are mostly internal non-infectious e.g., high blood pressure.
6. Ravi suffered from tuberculosis, while Rehman suffered from typhoid. Which disease
(CBSE, SA-2, 2011—14/B1)
caused more damage and why ?
Ans. Tuberculosis caused more damage. It is a chronic disease. It lasts for a long time
and has drastic long term effects on people’s health. Typhoid is an acute disease which
lasts for a short duration of time.
7. Differentiate between :
(i) acute and chronic disease.
(ii) congenital and acquired disease.
(CBSE, SA-2, 2011—34/A1)
(iii) infectious and non-infectious disease.
Ans. (i) Difference between acute and chronic diseases : Please see answer of Q. 3
(ii)
Congenital disease
Acquired disease
(a) These diseases are present
(a) These diseases are acquired after
from the birth.
birth during the lifespan of an
individual.
(b) These are inherited.
(b) These are not inherited.
154 / Reliable Question Bank (Solved)
(iii)
Infectious disease
Non-infectious disease
(a) These are spread from infected (a) These cannot spread from infected
person to a healthy person.
person to a healthy person.
(b) These are caused by attack of
(b) These are caused by factors other
pathogens.
than living pathogens.
8. (i) Name the organisms causing the following diseases :
(a) Kala-azar
(b) Sleeping sickness
(ii) Give one example each of acute and chronic disease. (CBSE, SA-2, 2011—31/B1)
Ans. (i) (a) Leishmania.
(b) Trypanosoma.
(ii) Acute disease
: Cough and cold
Chronic disease : Tuberculosis
9. Identify the diseases which spread through the following means. Also name the
target organs :
(i) Sexual contact
(ii) Mosquitoes
(iii) From air via nose
(CBSE, SA-2, 2011—19/A1)
Ans.
Means of spread
Disease
(i) Sexual contact
AIDS
(ii) Mosquitoes
Malaria
(iii) From air via nose
Tuberculosis
10. (i) Match the following columns with correct answer :
Target organs
Immune system
Liver
Lungs
Organism/Bacteria
Disease
(a) Leishmania
Worm
(b) Staphylococci
Kala-azar
(c) Trypanosoma
Acne
(d) Ascaris lumbricoides
Sleeping sickness
(ii) “High blood pressure can be caused by excessive weight and lack of exercise.”
Justify the statement.
(CBSE, SA-2, 2011—02/B1)
Ans. (i) (a) Leishmania
Kala-azar
(b) Staphylococci
Acne
(c) Trypanosoma
Sleeping sickness
(d) Ascaris lumbricoides
Worm
(ii) High blood pressure is an internal and non-infectious disease. Hence, the person
suffering from high blood pressure must control and schedule his/her daily diet.
13.3 INFECTIOUS DISEASES
Two Marks Questions (30 words)
1. Penicillin is not effective against common cold. Why ? (CBSE, SA-2, 2012—47024)
Ans. Penicillin is an antibiotic which blocks cell wall and formation of biochemical pathways.
Common cold is caused by virus which does not have any cell wall or biochemical
pathways. Hence, penicillin is not effective against it.
Science – IX (Why Do We Fall Ill) / 155
2. State any four ways by which an AIDS virus spreads from an infected person to a
healthy person.
(CBSE, SA-2, 2012—47032)
Or
Apart from sexual contact AIDS virus can be spread by which other two means ?
(CBSE, SA-2, 2012—47030)
Ans. • Blood to blood contact (transfusion).
• From an infected mother to her unborn baby during pregnancy, labour or delivery.
• Through breast feeding.
• Through injection needle that have been used by someone who is infected. (any two)
3. List any two ways of preventing the spread of air-borne diseases.
(CBSE, SA-2, 2012—47016)
Ans. (i) Avoiding direct contact with the infected persons.
(ii) Not sharing articles used by infected persons.
4. ‘Influenza or common cold, spreads faster and is difficult to control. Explain.
(CBSE, SA-2, 2012—47009)
Ans. Influenza or common cold is an air-borne disease which spreads easily and also
it is infectious, so its control is difficult.
5. If you go to the hospital to meet your friend suffering from malaria, what are the
chances of malaria spreading to you and your friends ? (CBSE, SA-2, 2012—1080, 47027)
Ans. Malaria is caused by plasmodium. It is carried by an insect/vector, female
anopheles mosquito.
6. AIDS is a fatal disease. Explain why ?
(CBSE, SA-2, 2012—47010)
Ans. In AIDS, immune system of the body is highly weakned and body suffers from
severe infections repeatedly. Hence, it is a fatal disease.
7. Name any diseases that can be prevented by using vaccines.
(CBSE, SA-2, 2012—47007)
Or
List four diseases for which vaccines have been developed.
(CBSE, SA-2, 2012—1010, 47019)
Ans. Diphtheria, Pertusis, Tetanus, Measles, Typhoid, Tuberculosis. (Any four)
8. (i) What is an epidemic disease ?
(ii) Which organ is affected if a person is suffering from jaundice ?
(CBSE, SA-2, 2012—47029; 2011—01/B1)
Ans. (i) An epidemic is the rapid and extensive spread of disease that affects many
individuals simultaneously in a particular area. It is generally an infectious disease.
(ii) Liver is affected.
9. Why are antibiotics effective against bacteria but not against viruses ?
(CBSE, SA-2, 2011—06/B1)
Ans. Antibiotics block the bacterial processes that build the cell wall. As s result, the
growing bacteria become unable to make cell walls and die easily. However, viruses have
few biochemical mechanism of their own and these instead use products of the host body.
Hence, these are unaffected by antibiotics.
156 / Reliable Question Bank (Solved)
10. State two consequences, which one has to face while dealing with an infectious
disease.
(CBSE, SA-2, 2011—06/B1)
Ans. (i) Body functions are damaged drastically and the infected person may require
long bed rest.
(ii) The person suffering from an infectious disease can serve as a source from where
the infection may further spread to other people.
11. Write two examples each of : (i) viral diseases
(ii) bacterial diseases.
(CBSE, SA-2, 2012—47023)
Ans. (i) AIDS, Dengue Fever
(ii) Typhoid, Cholera
12. What are infectious diseases ? Write two ways by which they can be controlled.
(CBSE, SA-2, 2012—47021)
Ans. Those diseases, which spread around fast are called infectious diseases. It is
controlled by :
(i) Washing hands before every meal.
(ii) Affected persons, avoided to going in public.
13. Which of the following diseases will cause major ill-effects on general health–
Elephantiasis, Cough and cold, Tuberculosis, Diarrhoea ? What are such diseases called ?
(CBSE, SA-2, 2012—47034)
Ans. Elephantiasis and Tuberculosis. These disease are called chronic diseases.
14. List the causative organisms for the following diseases :
(i) Kala-azar
(ii) Sleeping sickness
(CBSE, SA-2, 2012—47025)
(iii) Acne
(iv) AIDS
Ans. (i) Leishmania
(ii) Trypanosoma
(iii) Staphylococci
(iv) Human immune defeciency virus.
(CBSE, SA-2, 2012—1004)
15. What is an antibiotic ? Give its one example.
Ans. Antibiotic is a chemical substance secreted by microorganisms which can kill the
pathogens. Example : Penicillin.
16. With the help of an example explain how disease causing microbes spread
(CBSE, SA-2, 2012—47012)
through air ?
Ans. During coughing, sneezing or talking many disease causing microbes come out
from the body of infected persons and spread through air.
17. State two different ways by which infectious diseases spread ?
(CBSE, SA-2, 2012—47014)
Ans. (i) By air
(ii) By water
(iii) By vectors
(iv) By food.
(any two)
18. State in tabular form the modes of transmission of each of the following diseases :
(i) Syphilis
(ii) Tuberculosis (iii) Jaundice
(iv) Japanese encephalitis
(CBSE, SA-2, 2012—1076)
Ans.
Name of the disease
Syphilis
Tuberculosis
Jaundice
Japanese encephalitis
Mode of transmission
Sexual contact
Air
Water
Mosquito bite
Science – IX (Why Do We Fall Ill) / 157
19. Name a viral disease in which body can no longer fight off minor infections.
How does this disease spread from infected person to healthy person ?
(CBSE, SA-2, 2012—47017)
Ans. AIDS.
AIDS can be spread by following ways :
(i) Sexual contact.
(ii) Blood to blood contact.
(iii) From infected mother to her baby.
20. (i) What are vectors ?
(ii) In many species of mosquitoes the males do not prefer human blood, but females
do. State why ?
(CBSE, SA-2, 2012—1072)
Ans. (i) Animals that carry the infecting agents from a sick person to another potential
host are called vectors. Example : Dogs, Mosquitoes etc.
(ii) Female mosquitoes need highly nutritious food (in the form of blood) to lay mature eggs.
21. Name the causal organism of AIDS. Why a person suffering from AIDS cannot
fight even very minor infections ?
(CBSE, SA-2, 2012—1005, 47035)
Ans. HIV (virus). This virus goes to the human immune system and damages its
function. So, the body can no longer fight off even minor infections.
22. (i) What are communicable diseases ? Write its one example.
(ii) How do these spread ?
(CBSE, SA-2, 2012—47002)
Ans. (i) Diseases that get communicated from one affected person to the other are
called communicable diseases. Examples : Cough, Cold, Pneumonia.
(ii) These are spread by disease carrying microbes which are spread through the air,
water and vector.
23. What causes encephalitis ? How does it enter the body ? Which organ does it
infect ? What are the symptoms if this organ is infected ?
(CBSE, SA-2, 2012—1074)
Ans. • Virus causes encephalitis.
• Through mosquito bite it enters into human body.
• Brain is infected in this disease.
• Headache, fits, vomiting, unconsciousness.
24. Although Archana has been suffering from a cold and cough she decided to appear
for her class test. Classmates seated close to her had an exposure to the infection being
carried by Archana. However, only one of them actually suffered from cold and cough.
Explain, what prevented rest of those classmates catching cold and cough in spite of
their exposure to the infection.
(CBSE, SA-2, 2012—47001)
Ans. Immune system of individuals fight off infection carrying microbes. The immune
system of those who did not suffer with cold and cough successfully fought off the microbes
to which they were exposed.
25. How can we prevent water borne and vector borne infections ?
(CBSE, SA-2, 2012—1075)
Ans. • Water borne diseases can be prevented by providing safe drinking water.
• Vector borne diseases can be prevented by providing clean environment.
158 / Reliable Question Bank (Solved)
26. Health workers are exposed to more sick people than others in the community. Write
any four preventive measures they take to avoid sickness.
(CBSE, SA-2, 2012—1007)
Ans. (i) Hand washing after any direct contact with patients.
(ii) Wearing gloves while treating or examining the patient.
(iii) Proper disposal or sterilising the instruments.
(iv) Immunisation.
Three Marks Questions (50 words)
27. (i) Match the following columns with correct answers :
Column I
Column II
(a) Fungal disease
Dengue fever
(b) Viral disease
Cholera
(c) Protozoan disease
Skin disease
(d) Bacterial disease
Malaria
(ii) Name any one disease caused when the microbes target :
(a) Liver
(b) Lungs
(CBSE, SA-2, 2011—02/C1)
Ans. (i)
Column I
Column II
(a) Fungal disease
Skin disease
(b) Viral disease
Dengue fever
(c) Protozoan disease
Malaria
(d) Bacterial disease
Cholera
(ii) (a) Jaundice
(b) Cough and breathlessness
28. (i) Doctors diagnosed that Radha was suffering from HIV-AIDS. List any two methods
by which she might have contacted the disease. Name the organ affected by this disease.
(ii) Why antibiotics cannot be used for its treatment ? Justify your answer.
(CBSE, SA-2, 2011—14/B1)
Ans. Causes of AIDS :
(i) (a) Sexual contact with the infected person.
(b) Transmission of infected blood.
(c) Use of infected syringes, blades, or razors.
(d) Infected mother to her unborn child.
(e) Lymph nodes is affected from AIDS.
(any two)
(ii) Since it is caused by virus. Viruses have few biochemical mechanisms of their
own. They enter the host cell and use its machinery for their life processes, thus providing
few virus specific targets on which antibiotics can act.
29. (i) How does antibiotic penicillin work against bacterial infection ?
(ii) Name one bacterial disease that spreads through contaminated water.
(CBSE, SA-2, 2011—16/B1)
Ans. (i) The antibiotic penicillin blocks the bacterial processes that build the cell wall.
As a result bacteria die easily.
(ii) Cholera.
30. (i) Antibiotics do not work against viral infections. Give reason.
(ii) Name two viral infections transmitted by means of air.
(CBSE, SA-2, 2012—47023; 2011—20/A1)
Science – IX (Why Do We Fall Ill) / 159
Ans. (i) Viruses do not follow the same biochemical pathway as that in bacteria. The
antibacterial medicines (antibiotics) do not kill or remove viruses. Viruses live in the host
cells and use the cell's machinery for their life processes such as reproduction. So, antibiotics
are ineffective against viral diseases.
(ii) Common cold, influenza or measles.
31. What would be the symptoms if the microbe infects the following targets ?
(i) Lungs
(ii) Liver
(iii) Brain
(CBSE, SA-2, 2011—19/A1)
Ans. Lungs : Cough and breathlessness.
Liver : Jaundice.
Brain : Headaches, vomiting, fits, unconsciousness.
32. (i) Define antibiotic ? Explain how it is able to control bacterial infections but not
viral infections.
(ii) Write two water borne disease.
(CBSE, SA-2, 2011—18/A1)
Ans. (i) Antibiotics : (Anti-against; bio-living) Drugs/medicines used to kill the
infectious microbes (in the body to cure the person) are called antibiotics. They are produced
commercially by bacteria and fungi e.g. penicillin.
Reason for antibiotics are ineffective against viral diseases : Please see answer
of Q. 30(i).
(ii) Water borne diseases : (a) Cholera
(b) Diarrhoeal/amoebic dysentery
33. Answer the following questions :
(i) Write the expanded form of AIDS.
(ii) Name the pathogen of this disease.
(iii) List any two modes by which this disease is transmitted.
(CBSE, SA-2, 2011—24/B1)
Ans. (i) AIDS : Acquired Immuno Deficiency Syndrome.
(ii) HIV : Human Immuno Deficiency Virus.
(iii) Modes of transmission of AIDS : Please see answer of Q. 28(i)
34. In a slum area many people are reported to be suffering from malaria. Mention
the unhygienic conditions that must be prevailing there. Name the causative organism.
List various preventive measures.
(CBSE, SA-2, 2011—34/A1)
Ans. Unhygienic conditions–Stagnant water in the locality, lots of accumulation
of garbage.
Causative organism–protozoan [Plasmodium]
Preventive measures–Use of repellents, wire gauzing of doors, windows, periodic
spray of insecticides, etc.
35. It is diagnosed that Seema suffers from malaria.
(i) Which organ of Seema is affected ?
(ii) Which microbe is responsible for this disease ?
(iii) What is the symptom of this disease ?
(CBSE, SA-2, 2011—33/A1)
Ans. (i) In malaria liver gets affected.
(ii) Vector Plasmodium (casual) organism is responsible for this disease.
(iii) The signs and symptoms of a disease depend on the tissue or organ which the
microbe targets. Main symptom of malaria is high fever.
36. List three harmful effects of infectious disease.
(CBSE, SA-2, 2011—31/B1)
Ans. The three harmful effects of infectious disease are:
(i) When a person is suffering from a disease, their body functions are damaged and
may never recover completely.
160 / Reliable Question Bank (Solved)
(ii) Treatment of disease takes time and the person suffering is likely to be bedridden
for some time.
(iii) The person suffering serves as a source of infection to spread to other people.
37. (i) Explain why antibiotics are more effective in curing bacterial diseases than
viral diseases.
(ii) List two means of spreading of infectious diseases.
(CBSE, SA-2, 2011—08/C1)
Ans. (i) Antibiotics commonly block biochemical pathways important for bacteria. For
example many bacteria make a cell wall to protect themselves. The antibiotic penicillin
blocks the bacterial processes that build the cell walls and they die easily.
But antibiotics do not block chemical pathway of viruses. So, they are not effective
against viruses.
(ii) Means of spread of infectious diseases :
(a) Through air.
(b) Through water.
(c) Through sexual contact.
(d) Through vectors.
(any two)
38. (i) What are communicable diseases ?
(ii) What are the common methods of transmission of disease ?
(CBSE, SA-2, 2011—23/A1)
Ans. (i) Communicable diseases : Those diseases which are caused by pathogens/
infectious agents such as bacteria, viruses, fungi, protozoans, worms etc., are called
communicable diseases.
(ii) Several diseases spread from affected person to healthy person by means of water,
air, food, insect, physical contact etc.
Direct
t
contac
By air
deircet ct
In
Dir
tacct t
ccoonta
Infected
person
Healthy
person
By
food
Mosquito/
Insect
Doganimal
infected
Rabid
with rabies
Fig. Common methods of transmission of diseases.
39. What are the different means by which infectious diseases can spread ?
(CBSE, SA-2, 2011—29/B1)
Ans. Means of transmission of infectious disease :
(i) Through air e.g., common cold, T.B., etc. occur through little droplets thrown out
by an infected person when a person nearby breathes in these droplets. As a result
microbes get a chance to start a new infection.
(ii) Water borne e.g., Cholera. It occurs if the stool from someone suffering from an
infectious gut disease gets mixed with the drinking water used by the people living nearby.
Science – IX (Why Do We Fall Ill) / 161
(iii) Through vector e.g., malaria. It spreads through the bite of female Anopheles
mosquito which acts as a vector or carries a disease pathogen from one person to another.
40. A person was bitten by a stray dog. After some days his nature gets irritated, he
started fearing water.
(i) Name the disease.
(ii) Is there any vaccine available ?
(iii) Is there any plan of your local authority for the control of this disease ?
(CBSE, SA-2, 2011—29/A1)
Ans. (i) Rabies.
(ii) Anti-rabies vaccine.
(iii) Compulsory immunization of pets/dogs with anti-rabies vaccine.
41. How do diseases spread through air ? Name two such diseases.
(CBSE, SA-2, 2011—33/A1)
Ans. Some diseases spread through air. This occurs through the little droplets thrown
out by an infected person who sneezes or coughs. Someone standing close by can breathe
in these droplets and the microbes get a chance to start a new infection.
Two such diseases are common cold and pneumonia.
42. (i) Write few common signs and symptoms of a disease if brain is affected.
(ii) Give one local and one general effect of inflammation process.
(CBSE, SA-2, 2011—16/B1)
Ans. (i) Headaches, vomiting or fits
(ii) Local effects—swelling or pain
General effects—fever.
43. (i) Which system of our body is activated in response to infection and how it responds ?
(ii) Explain how HIV-AIDS virus affects and damages our body ?
(CBSE, SA-2, 2011—06/B1)
Ans. (i) Immune system is activated in response to infections. It responds by recruiting
many cells to the affected tissue to kill the disease causing microbes. This recruitment
process is called inflammation.
(ii) In HIV infection, the virus goes to the immune system and damages its function.
44. (i) Which part of the body is infected by malaria causing microbe ?
(ii) What are the two ways to treat an infectious disease ?(CBSE, SA-2, 2011—16/B1)
Ans. (i) Malaria causing microbes affect the liver and then red blood cell (RBC).
(ii) Ways to treat an infectious disease :
(a) By reducing the effect of disease.
(b) By killing the causative organisms of disease.
45. (i) Giving any four reasons, justify that it is difficult to prepare antiviral medicines
than antibiotics.
(CBSE, SA-2, 2011—24/B1)
(ii) Name the target organ of malaria.
Ans. (i) It is difficult to prepare antiviral medicines than antibiotics because:
(a) Viruses have few biochemical mechanisms of their own.
(b) They enter into our cells.
(c) They use our machinery for their life processes.
(d) Few virus specific targets to aim at.
(ii) Liver.
162 / Reliable Question Bank (Solved)
46. Why is it difficult to develop vaccine for viral diseases?(CBSE, SA-2, 2011—19/B1)
Ans. Viruses are very specific to host. They live and multiply only in the living cells.
They cannot be cultured on artificial medium, hence it is difficult to develop a vaccine for
viral diseases.
47. Give cause and remedy of :
(i) Hepatitis (ii) AIDS
(iii) Malaria
(CBSE, SA-2, 2011—29/B1)
Ans.
Disease
Cause
Remedy
(i) Hepatitis
Hepatitis virus
• Avoid stale food.
• Vaccination of Hepatitis A&B
(ii) AIDS
HIV
• Avoid use of used syringes and
blades. Avoid sexual contact.
(iii) Malaria
Anopheles mosquitoes • Proper arrangement of hygienic
condition and not letting water
stagnate for their breeding.
• Use mosquito repellant.
48. What are the principles of treatment of a disease ?
(CBSE, SA-2, 2012—1011; 2011—18/B1)
Ans. Principles of treatment of disease :
There are two ways to treat an infectious disease :
(i) One would be to reduce the effect of the disease—
(a) By symptomatic treatment.
(b) By taking a bed rest.
(ii) Killing the micro-organisms of infectious agents.
49. (i) Name two diseases for which the children below the age of one year should
be vaccinated.
(ii) What are the symptoms shown by a person if :
(a) lungs get infected ?
(b) stomach is infected ?
(CBSE, SA-2, 2011—18/B1)
Ans. (i) BCG and DPT.
(ii) (a) Cough and breathless.
(b) Stomach ache, loose motion, vomiting.
50. (i) Which of the following diseases are caused by protozoan ?
Dengue, Malaria, Kala-azar and HIV–AIDS
(ii) Suggest any two ways to prevent being infected by protozoa.
(CBSE, SA-2, 2011—01/B1)
Ans. (i) Malaria and Kala-azar
(ii) (a) Take care not to have stagnant water around.
(b) Proper waste disposal.
51. (i) Why taking an antibiotic is not effective in the common cold ?
(ii) Name two diseases against which infants below one year are vaccinated.
(iii) List two symptoms of any one of these diseases.
(CBSE, SA-2, 2011—01/B1)
Ans. (i) Common cold is a viral disease so antibiotic is not effective against it.
(ii) Measles, tetanus.
Science – IX (Why Do We Fall Ill) / 163
(iii) Symptoms of measles :
(a) Fever
(b) Sore throat
(c) Cough
(d) Sore eyes
(e) Running nose
(any two)
52. (i) List two causes of spread of typhoid.
(ii) Mention two ways by which we can prevent the spread of this disease.
(CBSE, SA-2, 2011—24/A1)
Ans. (i) Typhoid is spread :
(a) Through contaminated food and water.
(b) Through house flies.
(ii) We can prevent typhoid by :
(a) Underground disposal of human faeces.
(b) Disinfection of water and proper cooking of food.
53. (i) If a person is suffering from jaundice, name the mode of its transmission and
the organ affected by this disease.
(ii) List one general mode of prevention of jaundice.
(iii) It has been observed that despite the availability of the vaccine for Hepatitis A in
the market, it may not be necessary to be given to children by the time they are five
(CBSE, SA-2, 2011—14/B1)
years old. Why ?
Ans. (i) Water, Liver
(ii) Provide safe drinking water.
(iii) By the time children are five years old they may be immune to hepatitis A. This
is because they are exposed to the virus through unclean or contaminated drinking water
due to lack of hygienic conditions or poverty.
54. (i) Mention two factors on which severity of disease manifestation depends.
(ii) Once you have been infected with small pox, there is no chance of suffering from
it again. Give reason.
(CBSE, SA-2, 2011—18/A1)
(iii) Mention the two ways of preventing ‘disease’.
Ans. (i) Severity of disease manifestation depends upon the following factors:
(a) Number of microbes attached to the body.
(b) Immune system of the individual.
(ii) This happens because when the immune system first sees an infectious microbe, it
responds against it and remembers it specifically. So, the next time when that particular
microbes, or its close relative enters the body, the immune system responds with even greater
vigour. This eliminates the infections even more quickly than the first time around.
(iii) Ways of preventing disease :
(a) By sanitation
(b) By eradication
(c) By vaccination
55. “Prevention of disease is more desirable than its treatment.” Justify the statement
by discussing three major strategies to be adopted for the prevention of infectious diseases.
(CBSE, SA-2, 2011—02/C1)
Ans. To prevent infectious diseases following strategies have to be adopted :
(i) Provide safe drinking water and public hygiene : We can prevent the
exposure to infectious microbes by providing safe drinking water and clean environment.
(ii) Provide proper and sufficient food : Availability of proper and sufficient food
for everyone is the basic principle of prevention of infectious disease.
(iii) Immunisation programme : This would prevent any subsequent exposure to
the infecting microbe from turning into actual disease.
164 / Reliable Question Bank (Solved)
56. (i) State in brief the principle of immunisation.
(ii) Name any two diseases that can be prevented by immunisation.
(CBSE, SA-2, 2012—1073, 47004; 2011—02/B1)
Ans. (i) Principle of immunisation : When the immune system first sees an
infectious microbe, it responds against this and then remembers it specifically. The next
time when that particular microbe or its close relative enters the body, the immune system
responds more vigorously. This eliminates the infection more quickly than the first time
around. This is the principle of immunisation.
(ii) The diseases that can be prevented by immunisation are :
Tetanus, diphtheria, whooping cough, measles, polio.
57. What is human immune system ? What is a vaccine ? How immunisation can be
(CBSE, SA-2, 2011—08/C1)
achieved ?
Ans. Human immune system : Immune system of our body is made up of “immune
cells” which kill the infecting microbes which enter the body.
Vaccine : “Vaccine” is the weak form of microbe of infecting disease which was rubbed
into the skin of healthy person deliberately.
For how immunization can be achieved ? Please see Answer of Q. 56(i).
58. In previous years a group of people did not have the fear of contacting persons
exposed to small pox and would provide nursing care for the victims. Discuss why ?
(CBSE, SA-2, 2011—19/A1)
Ans. Having a disease once was a means of preventing subsequent attacks of the
same disease. When the immune system first sees an infectious microbe, it responds against
it and then remembers it specifically. Next time that particular microbe or its close relative
enters the body the immune system responds with even greater vigour and thus
eliminating the infection. So if you had small pox once, there is no chance of suffering
from it again.
59. (i) Mohan suffered from chicken pox in his childhood. He would not suffer from
this disease again. Mention reason for this.
(ii) On which factor the severity of disease manifestation depends ? Explain with an
(CBSE, SA-2, 2011—24/A1)
example.
Ans. (i) Mohan has developed lifelong immunity against the disease.
(ii) Severity of disease manifestation depends upon number of microbes in the body.
(a) If number of microbes is very small, the disease manifestation is minor.
(b) If the number of some microbe is larger, then disease can be severe.
60. (i) Why a person suffering from AIDS cannot fight even small infections ?
(ii) In a slum area many people are suffering from malaria. Mention any two
unhygienic conditions that must be prevailing in that locality.
(iii) Why female Anopheles mosquito feeds on human blood ?
(CBSE, SA-2, 2011—24/A1)
Ans. (i) AIDS is caused by HIV which damages the immune system of the person
suffering from it.
(ii) (a) Stagnant water in ditches.
(b) Breeding ground for mosquitoes.
(iii) Female Anopheles mosquitoes require large amount of protein to lay their eggs.
So, they feed on human blood which is rich in protein.
Science – IX (Why Do We Fall Ill) / 165
61. (i) How can we prevent diseases ?
(CBSE, SA-2, 2011—23/A1)
(ii) What is immunization ?
Ans. (i) We can prevent disease by two ways :
(a) General ways : • By preventing exposure to infectious microbes.
• By providing safe drinking water and public hygiene.
• By providing proper and balanced diet.
(any two)
(b) Specific ways : • By immunisation.
(ii) Immunisation : When a vaccine is used to kill the microbes to prevent their
entry into the body, the immune power of the body improves. So, the process of developing
immune power in the body to fight against the diseases is called immunisation.
62. Suggest three ways to prevent spreading of infectious diseases.
(CBSE, SA-2, 2011—20/B1)
Ans. We can prevent spreading of infectious diseases by :
(i) Getting immunized through vaccines at the right time.
(ii) Building an immunity by taking balanced diet every day.
(iii) Keeping our surroundings clean and maintaining public hygiene.
63. How principle of immunization is implemented for eliminating polio ?
(CBSE, SA-2, 2011—20/B1)
Ans. Oral vaccines of polio are given periodically to children under five years of age.
These vaccines are preparation of weakened infectious agents. These preparations stimulate
the body to produce antibiotics against those antigens. Thus, body becomes immune to
the polio disease.
64. Explain giving reasons :
(i) Some children fall ill more frequently than others living in the same location.
(ii) AIDS is considered to be ‘syndrome’ and not a disease.
(CBSE, SA-2, 2012—47007)
(iii) Antibiotics are not effective for viral diseases.
Ans. (i) It is due to immunity, economical and social stability of different people.
(ii) Loss of immunity in AIDS, makes a person susceptible to diseases. So, AIDS is
considered as syndrome.
(iii) Viruses have few biochemical mechanism of their own and use the machinery of
our life process.
65. (i) Which of these is an acute ailment and why : Tuberculosis, Cancer, Diarrhoea,
Elephantiasis ?
(ii) State any two internal, non-infectious causes of a disease.
(iii) Name the organ that is targeted by the virus that causes jaundice.
(CBSE, SA-2, 2012—47031)
Ans. (i) Diarrhoea, since it is a short term disease and does not cause drastic long
term effects on persons’s general health.
(ii) Genetic abnormalities, excessive weight.
(iii) Liver.
66. (i) While going abroad why is it essential to get vaccinated against certain diseases ?
(ii) Name a vaccine which saves the life of babies from three diseases.
(iii) A person is suffering from chest pain, breathlessness, loss of body weight, persistent
cough and produces blood stained sputum ? Name the disease.
(CBSE, SA-2, 2012—1080, 47027)
166 / Reliable Question Bank (Solved)
Ans. (i) A person may be carrier of a disease. Such a person can carry disease to a
foreign country.
(ii) DPT vaccine.
(iii) Tuberculosis.
67. State the method of transmission of each of the following diseases :
(i) (a) Cholera
(b) Aids
(c) Malaria
(d) Pneumonia.
(ii) Name the diseases a person will get if the disease causing microbes target the
(CBSE, SA-2, 2012—1079, 47026)
liver of a person.
Ans. (i) (a) Contaminated water
(b) Sexual contact
(c) Mosquito
(d) Air.
(ii) Jaundice
68. (i) If penicillin is given to a patient suffering from jaundice, it doesn’t have any
effect on the infection. Why ?
(ii) Name a disease which has been eradicated from the world.
(iii) State the principle behind its eradication.
(CBSE, SA-2, 2012—47025)
Ans. (i) Jaundice is caused by virus. Penicillin is an antibiotic which can block
biochemical pathways in bacteria. Viruses do not use such pathway.
(ii) Small pox.
(iii) Based on the principle of immunisation by small pox vaccine.
69. Explain when is a disease categorised as a communicable disease. Give two examples
each of diseases communicated through (i) air and (ii) water. (CBSE, SA-2, 2012—47017)
Ans. When the microbial agents causing a disease move from one affected person to
some healthy person through air, water or vector.
(i) Air borne communicable diseases : Common cold, Pneumonia, Tuberculosis.
(ii) Water borne communicable diseases : Cholera, Jaundice.
70. Write three precautions you can take in your school to reduce the incidence of
infectious diseases.
(CBSE, SA-2, 2012—47002)
Ans. (i) Children carrying infectious disease should be allowed leaves.
(ii) Spreading awareness about diseases.
(iii) Use of disinfactant.
(iv) Keeping drinking water and surroundings clean. (any three)
71. Name diseases which are caused by–(two for each)
(i) virus
(ii) bacteria
(iii) protozoa
(CBSE, SA-2, 2012—47005)
Ans. (i) Common cold, Influenza, AIDS.
(ii) Typhoid, Cholera, Tuberculosis.
(iii) Malaria, Kala-azar.
72. “Prevention is better than cure”. Suggest three methods to prevent the spread of
infectious diseases.
(CBSE, SA-2, 2012—47024)
Ans. (i) Preventing exposure to infections.
(ii) Availability of proper and sufficient food.
(iii) Taking vaccines against a particular disease.
73. The general way of preventing infections mostly relate to preventing exposure to the
disease agent. Explain the statement with three examples.
(CBSE, SA-2, 2012—47030)
Ans. (i) Air borne diseases can be prevented by providing living conditions that are
not overcrowded and by using face masks during epidemic.
Science – IX (Why Do We Fall Ill) / 167
(ii) Water-borne diseases can be prevented by providing safe-drinking water.
(iii) By providing clean environment (through proper disposal of garbage, not allowing
stagnation of water and proper sanitation), vector borne diseases can be prevented.
74. State reason for the following statements :
(i) Children at the time of birth must be given proper vaccination.
(ii) A person suffering from diseases like Tuberculosis, Flu should be advised to avoid
close public contact.
(iii) Personal hygiene is very essential for good health. (CBSE, SA-2, 2012—47021)
Ans. (i) To prevent whole range of infectious diseases and provide a disease-specific
means of prevention, there are vaccines against tetanus, diphtheria, whooping cough etc.
(ii) These are air borne diseases that will spread.
(iii) Personal hygiene reduces exposure to infectious agents. Prevention of disease is
more desirable than its successful treatment.
75. Write the symptoms when following organs are targeted by microbes :
(CBSE, SA-2, 2012—1005, 47035)
(i) Lungs
(ii) Liver
(iii) Brain.
Ans. (i) Cough or breathlessness.
(ii) Jaundice.
(iii) Headache.
76. (i) For most microbes the organ they target is related to their point of entry.
Furnish details of your answer under the following headings :
Organ of entry
Mouth
Mouth
(ii) State the two important
Kind of microbe
Target organ
Disease caused
Bacteria
Virus
ways by which an infectious disease can be treated.
(CBSE, SA-2, 2012—1072)
Ans. (i)
Organ of entry
Kind of microbe
Target organ
Disease caused
Mouth
Bacteria
Gut lining
Typhoid
Mouth
Virus
Liver
Jaundice
(ii) (a) To reduce the effects of the disease.
(b) To kill the cause of the disease.
77. Explain any three reasons to justify that prevention of diseases is better than
than cure.
(CBSE, SA-2, 2012—47001, 47022)
Ans. “Prevention is better than cure” due to the following reasons :
(i) Once a person has a disease, then body functions are damaged and may not
recover completely.
(ii) The treatment may take time and so the person will be sick for a longer period of time.
(iii) Infectious person is the source from where infection spreads to other person.
78. Same drug does not work against the microbes belonging to different groups.
Why ? State the mechanism of antibiotics in killing bacteria. (CBSE, SA-2, 2012—1007)
Ans. Every micro-organism has its own biochemical cycle. So one type of antibiotic
can stop or block biochemical cycle of one type of micro-organism only but not all type of
micro-organisms. Antibiotics destroy the cell wall during the asexual reproduction cycle,
hence the bacteria can be easily killed.
168 / Reliable Question Bank (Solved)
VALUE BASED QUESTIONS
Q. 1. (i) The disease causing factors which are present within the human
body are called intrinsic factors. The diseases caused by these factors are called
metabolic diseases. Name two such diseases.
(ii) The disease causing factors which enter the human body from outside
source are called extrinsic factors. Name two diseases caused by these factors.
Ans. (i) Diabetes and cataract.
(ii) Malaria and chickenpox.
Q. 2. (i) Give an example of a disease (other than elephantiasis) which
spreads slowly and lasts for a long time (it is curable).
(ii) Name two diseases which are caused in due course of time and last life
long (They can be kept in control but cannot be cured permanently).
(iii) The diseases which are present since birth are called congenital diseases.
What is the cause of this disease?
Ans. (i) Tuberculosis. (ii) Diabetes and Cardiovascular disease.
(iii) They are caused due to metabolic disorder or genetic abnormality.
Q. 3. (i) Virus, bacteria, fungus and protozoa are disease causing organisms.
Give one term to describe them.
(ii) One of the above microorganism is non-cellular and considered to be
on the border line of living and dead. Name the organism.
Ans. (i) Pathogen, (ii) Virus.
Q. 4. A particular disease leads to loss of water from body tissues and makes
the patient seriously ill in a short span of time. What can be given to the patient
to prevent this loss of water ?
Ans. Oral Rehydration Solution (ORS) can be given to prevent dehydration during
diarrhoea.
Q. 5. A chemical substance is produced by a microorganism (generally
bacteria), which has the capacity, in dilute solutions, to inhibit the growth of
or to kill other micro-organisms. These are sufficiently non-toxic to the host.
Name two diseases against which this chemical is ineffective.
Ans. Antibiotics are ineffective against malaria and jaundice.
Q. 6. A particular substance is introduced into the body to trigger the
production of specific antibodies to confer immunity against subsequent infection.
Name the substance. Name a disease which is prevented by this process.
Ans. Antigens introduced by the process of vaccination prevents polio.
Q. 7. What are the body’s defenses against diseases ?
Ans. The body has three lines of defence :
(i) Skin, (ii) White blood cells, (iii) Antibodies (antigens and lymphocytes)
Q. 8. (i) What is balanced diet ?
(ii) What problems will you face if you do not eat a balanced diet ?
Ans. (i) A diet that contains adequate amounts of fibre (roughage), water and all
other necessary nutrients (protein, fat, carbohydrate, vitamins and minerals) required
for healthy growth and activity, is called balanced diet.
(ii) Lack of balanced diet will lead to the following problems :
(a) Poor maintenance of body tissues and organs.
(b) Lack of proper growth and development of the body.
(c) Lack of energy.
(d) Improper functioning of the various systems of the body.
All this will ultimately lead to some illness.