CBSE Class 9 Biology Why Do We Fall Ill Worksheet Set C

CBSE Class 9 Biology Worksheet - Why do we fall ill? - Practice worksheets for CBSE students. Prepared by teachers of the best CBSE schools in India.

SUBJECT BIOLOGY CLASS- IX

TERM-SA2

TOPIC- Why do we fall ill?

Q1 Why does taking medicines does not reduce the severity or the duration of the disease if we have a common cold?

Q2 Why do doctors sometimes prescribe antibiotics when we have a viral cold?

Q3 Not all persons exposed to a particular microbe suffer from the disease caused by it. If we become exposed to or infected with an infectious microbe it does not necessarily mean that we will develop a noticeable disease. Why not?

Q4 What is the importance of childhood immunisation under the Public Health Programme?

Q5 Why is it important to know the category to which an infectious agent of a  disease belong?

Q6 How does mosquito act as a vector of malaria?

Q7 Explain the terms - Immunisation, Immunity, vaccination, Vaccine.

Q8 How did Edward Jenner discover vaccination?

Q9 What are the limitations of the approach to dealing with infectious disease through symptom-directed treatment and use of medicines that kill microbes?

Q10 What is the basis of the principle of immunization?

Exam Questions NCERT Class 9 Science Chapter 13 Why do we fall ill

Question. Why can we not make antiviral drugs?
Ans : The viruses lie on the border of living and non-living organism. The virus needs a host body to live and multiply. They cannot be grown and their biological pathways cannot be affected. Hence, the anti-viral drugs is difficult to make. 

Question. Name the diseases which’ are caused by :
Ans : Bacteria : TB, Typhoid, Anthrax and Tetanus. Viruses : Common Cold, AIDS, Dengue fever and Mumps. Fungi : Ring worm, Skin infections and Athlete’s foot. Protozoa : Malaria, Kala-Azar, Sleeping Sickness and Amoebiasis.

Question. Define carriers. Give two examples.
Ans : Carriers are the organisms which harbor diseasecausing germs without showing away sign of disease themselves, but have the ability to infect other healthy individuals. For example : Housefly, female insect Anopheles.

Question. The body of a patient has lost its power of fighting against infections. Which disease may the patient be suffering from? Name the pathogen and describe any two modes of its transmission from the patient to other person.
Ans : Patient is suffering from AIDS. HIV (Human Immuno deficiency Virus) can be transmitted by : (1) sexual contact with infected person. (2) the use infected syringe.

Question. What are the different types of diseases? Explain them.
Ans : Diseases are broadly grouped into two types : Communicable or infectious disease : Those diseases which are passed on from one person to another in various ways through air, water, food, physical contact and insects.
Non-communicable diseases : Those diseases which cannot be spread from person to person. For example : Arthritis, marasmus, etc.

Question. What is immunization, immune system, immunity?
Ans : (i) Immunization is a specific method of preventing diseases by inoculating vaccines in the human body.
(ii) Immune system : It is a system which protect our body against infection.
(iii) Immunity : The body’s power to resist and overcome infection is called immunity.

Question. Give four modes of transmission of AIDS.
Ans : (i) Blood to blood contact (transfusion).
(ii) From an infected mother to her unborn baby during pregnancy, labour or delivery.
(iii) Through breast feeding.

Question. How can we prevent air borne diseases?
Ans : Air borne disease can be prevented by some simple measures. If you are suffering from common cold then you should cover your face while sneezing or coughing. In case of a flu scare in the city, you should wear a face mask while going to a public place or traveling by public transport. Our body easily wards off any future onslaught of that microbe. Many diseases can be prevented by vaccines.

Question. How can we prevent water borne diseases?
Ans : Water borne disease can be prevented by avoiding the use of contaminated water. You should always carry drinking water from home. If that is not possible then you should buy bottled water for drinking. Never buy food from those vendors who do not keep their food items covered. Don’t eat stale or spoiled food items.

Question. What precautions can you take in your school to reduce the incidence of infectious diseases?
Ans : The following precautions can be taken in my school to reduce the incidence of infectious diseases :
(i) Isolation of infected students to prevent the spreading of air borne diseases. (ii) Availability of clean drinking water.
(iii) Clean surroundings to stop the growth and multiplication of vectors. (iv) Starting public health programme of childhood immunisation.
(v) Spreading awareness through lectures and seminars about prevention and health concept.

Question. “On exposure with an infectious microbe does not necessarily mean developing noticeable disease.” Do you agree? Explain with reason. If yes, how severe infections occur in our body?
Ans : Yes. I agree with the statement. The severity of disease manifestations depends on the number of microbes in the body. If the number of microbes is very small, the disease manifestations may be minor or unnoticed. But if the number of the microbes is large, the disease can be severe enough to be life-threatening. The immune system is also a major factor that determines the number of microbes surviving in the body. The cells of immune system go into action each time infecting microbes enter the body. If they are successful, we do not actually come down with any disease and the manifestation of the disease will be minor. However, if the immune system fails, severe infections occur in the body.

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