Tuesday, December 8, 2015

class9 why do we fall ill solved questions


1. Define health.

Ans. Health is defined as the state of complete physical, mental and social well being.

2. What is disease?
Ans. Disease is a departure from normal health through structural or functional disorder of the body.

3. What is the most important factor that keeps us healthy?

Ans. Our social environment is an important factor in our individual health.

4. List any two conditions essential for good health.

Ans. Conditions essential for good health are:

i. to have a balanced diet and varied diet.

ii. avoid wrong habits like drinking alcohol and drug consumption.

5. List any two conditions essential for being free of disease.

Ans. Conditions essential for being free of disease are:

i. maintain personal hygeine.

ii. keep environment clean and hygiene.

6. Give examples of diseases which are caused by intrinsic sources and extrinsic sources.

Ans. Diseases caused by intrinsic sources:  Heart attack, Kidney failure, Sickle cell anaemia, Diabetes, etc.

Diseases caused by extrinsic sources:  Night blindness, Malaria, Rabies, Hepatitis, Dysentery, etc.

7. Why is public cleanliness important for individual health?

Ans. Many public places are left messy and unsightly. Some industries pollute the environment. In many  drains water flows uncovered or water is stagnant. All these enhance the growth of germs and chances  of infection. Therefore, public cleanliness is important for individual health.

8. Give at least two examples of each:i. Physical diseases       ii. Mental disease     iii. Deficiency diseases

Ans. i. Cold and bone fracture     ii. Depression ,Schizophrenia     iii. Night blindness and Scurvy

9. Enlist some intrinsic and extrinsic factors which affect human health.

Ans. Intrinsic factors:
i. Malfunctioning of some vital body organs and immune systems
ii. Genetic disorder        
iii. Hormonal imbalance
Extrinsic factors:
i. Unbalanced or inadequate diet
ii. Disease causing organisms
iii. Pollutants
iv. Bad food and drinking habits

10.What do you mean by symptoms of diseases?

Ans. Symptoms of disease are the things we feel as being ‘wrong’. Symptoms are the physical or behavioral signs of a suspected injury or disease.

11.Define communicable diseases.

Ans. Communicable disease is defined as the disease that is transmitted through direct contact with 
an  infected individual or indirectly through a vector.

12.Differentiate between acute and chronic diseases.


Acute Diseases
Chronic Diseases
Last for short duration.
Last for long duration
Damage to body
Cause less damage to
Cause great damage to

body tissues and parts
body tissues and parts
Common cold

13.Give one word for:

i. Diseases which can spread from one person to another 

ii. Diseases which are present since birth

iii. Diseases which last for short duration

iv. Disease which last for longer duration

Ans. i. Infectious diseases or communicable diseases               ii. Congenital diseases

iii. Acute diseases                                                                      iv. Chronic diseases

14.Give examples of:
i. Infectious diseases     ii. Non-infectious diseases    iii. Acute diseases    iv. Chronic diseases

Ans. i. Malaria              ii. Heart-attack                       iii. Common cold     iv. Tuberculosis

15.What do you understand by non-communicable diseases?

Ans. A non-communicable disease a disease which do not spread through direct contact with an
infected individual or indirectly through vector. Such diseases may result from genetic or lifestyle 

16.What are the causes of non-infectious diseases?

Ans. Following are the causes of non-infectious diseases:
i. deficiency of certain essential substances in our diet
ii. degeneration and wearing out of tissues
iii. uncontrolled proliferation of tissues in any part of body
iv. defects in metabolic pathways
v. damage and injuries of tissues and body parts by accidents

17.What are congenital disorders? How do they occur? Can they be cured?

Ans. Congenital disease is a disease or disorder that is inherited genetically and present at the time of
These diseases are caused because of genetic abnormalities, metabolic disorders or malfunctioning of
any organ in body.
No, congenital diseases cannot be cured. They are permanent.

18.Which antiviral protein is secreted by our body in case of viral infection?

Ans. Interferon is secreted by our body in case of viral infection.

19.Name the bacteria that are responsible for peptic ulcers.

Ans. Helicobacter pylori is responsible for peptic ulcers.

20.Why does a man suffering from an acute disease suffer less than a man suffering from a chronic disease?

Ans. Chronic diseases last a long time and hence, they damage body parts and tissues to a greater extent than an acute disease, which lasts for a very short duration. Therefore, a patient suffering from a chronic disease endures more agony than a patient suffering from an acute disease.

21.Define vector.

Ans. Vector is defined as an agent (person or animal or microorganism) that carries and transmit a disease.

22.Which viral disease suppresses bodies immune system?


23.What is vaccination?

Ans. The process of injecting killed or attenuated microbes in order to activate the immune system against disease causing microbes to prevent from disease/s is vaccination.

24.Name the causative agent of sleeping sickness.

Ans. Sleeping sickness is caused by Trypanosoma.

25.Give at least one example of each:

i. disease caused by bacteria                    ii. disease caused by virus

iii. disease caused by protozoa               iv. disease spread through vector

Ans. i. Tuberculosis ii. Jaundice iii. Sleeping sickness iv. Malaria

26. Name the organs which are mainly affected by the following diseases:
i. Jaundice               ii. Hepatitis                   iii. AIDS                     iv. Encephalitis

Ans. i. Liver ii. Liver iii. Immune system iv. Brain

27.What preventive measures can be taken against infectious diseases?

Ans. Diseases can be prevented in general and specific ways.

a. General ways of prevention are:

I. Community hygiene is one of the basic methods to the prevention of infectious diseases

II. Air-borne diseases can be controlled by making living conditions that are not overcrowded.

III. Water-borne diseases can be prevented by providing safe drinking water.

IV. Vector-borne infections can be checked by making vector free environment

V. Specific way of preventing infectious diseases is to immunize surrounding individuals against infectious diseases (if possible).

28.Write the causative agents for the following diseases:

i. Tuberculosis               ii. Jaundice                  iii. Malaria             iv. Polio

Ans. i. Mycobacterium tuberculosis ii. Hepatitis B virus iii. Plasmodium sp. iv. Polio virus

29.What are the different modes of transmission of diseases? Also give examples of diseases of each mode of transmission.

Ans. Infectious diseases can be spread through the following agents:

1) Through air: Cough or sneeze of an infected person may cause infection to a healthy person if he inhales the droplets containing microbes. Diseases like common-cold, tuberculosis, pneumonia, etc.,  are  spread through air.

2) Through water: Consumption of water contaminated with the spores of bacteria or disease causing microbes can cause disease like cholera, amoebiasis.

3) Through sexual contact: Unsafe sexual contact with an infected partner many lead to may sexually transmitted diseases. For example, syphilis, AIDS, genital warts, etc.

4) Through vectors: Vectors (animals or microorganisms) carry the infecting agents from a sick person to another potential host. They act as a carrier of a disease or infection. Malaria is a very good example of this type of transmission of diseases.

30.How do antibiotics work against bacteria?

Ans. Antibiotics are drugs used to treat infections caused by bacteria. Some antibiotics, such as the penicillins, are 'bactericidal'. They work by killing bacteria. They do this by interfering with the 
formation  of the cell walls or cell contents of the bacteria. As a result bacteria die. Other antibiotics are  'bacteriostatic'. They work by stopping bacteria multiplying. Excess use of antibiotics can lead to 
bacteria  becoming resistant to them so it's important to only take them when necessary.

Class IX Biology Chapter Chapter: Why do we fall ill? NCERT Solutions 
Biology Science Ch-13. Why do we fall ill 
CCE Test Paper Biology Chapter: Why do we fall ill? Solved Questions 
NCERT Solved Board Questions for Class 9th Science: Ch-13. Why do we fall ill? 
Class IX Biology Ch-13.Why do we fall ill-Chapter Notes 


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