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

CBSE Class 9 Biology Worksheet - Why do we fall ill

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

Question. Name the causal organism of AIDS. Why a person suffering from AIDS cannot fight even very minor infections?
Ans : HIV is the causal organism of AIDS. This virus goes to the human immune system, thus can damage the bodily function. So, the body can no longer fight off even very minor infections.

Question. What is an antibiotic?
Ans : A substance which stops the growth of bacteria or kills the bacteria is called antibiotic. Antibiotic is given to treat or prevent bacterial infection.

Question. How do we know that someone is suffering from disease?
Ans : Signs and symptoms indicate presence of a particular disease. Because when there is a disease, either the functioning or the appearance of one or more systems of the body will change for the worse.

Question. What are vectors for a disease?
Ans : Some animals work as vehicles to transfer infection from one person to another. Such animals are called vectors.

Question. Which animal plays the role of vector for rabies?
Ans : Dogs, cats, mongoose, monkey.

Question. What do you understand by symptoms?
Ans : Apparent signs which give a clue about an underlying disease are called symptoms. For example : Headache, fever, abdominal cramps, etc.

Question. You have suffered from chickenpox, when you were in class three. Why will you not suffer from it again?
Ans : As I suffered from chickenpox, when I were in class three. I got well by cure. Now, my immune system has developed antibodies against it.

Question. Common cold spreads faster and is difficult to control. Give reason.
Ans : Common cold is a communicable and air borne disease, i.e., the microbes spread through the air. Thus, common cold spreads faster and is difficult to control.

Question. What is disease?
Ans : Anything which interferes with the normal functioning of the body and impairs the health. 38. What is Incubation Period? Ans : It is the period between the infection and the appearance of the first symptom.

Question. Which was the first Antibiotic?
Ans : Penicillin was the first antibiotic which was invented by Alaxander Flamming in 1928.

Question. A child goes to a party and come back with cough, running nose, headache and fever. What could be the possible disease? Name the pathogen causing it.
Ans : It could be influenza caused by the virus.
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Question. Why is Vaccination of children necessary?
Ans : Children are more vulnerable and susceptible to diseases and are hence given vaccines so they are able to develop immunity against diseases.

Question. (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?
Ans : (i) AIDS is caused by HIV which damages the immune system of the person suffering from it. Thus, the person cannot fight even small infections.
(ii) Stagnant water in the surroundings and accumulation of garbage.
(iii) Because Female Anopheles mosquitoes require large amount of proteins to lay their eggs.

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