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

Question. Name the target organs for the following diseases :
(i) Hepatitis targets _____
(ii) Fits or unconsciousness targets _____
(iii) Pneumonia targets _____
(iv) Fungal disease targets _____
Ans : (i) liver, (ii) brain, (iii) lungs, (iv) skin.

Question. Penicillin is not effective against common cold. Why?
Ans : Penicillin is an antibiotic which blocks the formation of biochemical pathways. Common cold is caused by virus which does not have any cell wall. Hence, penicillin is not effective against it.

Question. Why making anti-viral medicines is harder than making anti-bacterial medicines?
Ans : Antibiotics block the biochemical pathways important for bacteria which inhibit growth of bacteria or kill them. However, viruses do not use biochemical pathways like bacteria. Hence, these remain unaffected by antibiotics.

Question. Which amongst the two diseases : acute or chronic has adverse effect on the health of a person? Explain giving a suitable example.
Ans : Chronic disease lasts for long time so it is more harmful than acute disease. For example : Cough and cold, viral fever are acute diseases which do not affect our health badly and we become well within a week or so while tuberculosis (TB) which is a chronic disease affects health drastically and has a long time effect on our body.

Question. What do signs and symptoms indicate if a person is suffering from any 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 do you mean by active and passive immunisation?
Ans : Active immunisation : It promotes the production of circulating antibodies against foreign antigens by injecting a small quantity of modified antigen into the bloodstream.
Passive immunisation : It is the application of antibodies from an immune individual to non-immune patient. This treatment is used when an individual has been or probably will be, exposed to an infectious disease and there is insufficient time for active immunisation.

Question. What are limitations for the approach to deal with infectious diseases?
Ans : Three limitations are :
(i) If someone is suffering from disease, his body function will disturb.
(ii) Treatment will take time.
(iii) Infectious person can be a source of spreading infection.

Question. What do you understand by non-infectious disease?
Ans : When a disease happens because of some malfunctioning in any organ and it is not because of any microorganism, it is called non-infectious disease. A non-infectious disease may happen because of a wrong lifestyle. Some non-infectious diseases may happen because of genetic factor, i.e., they are right from the birth. Example : Diabetes, hypertension, heart disease, arthritis, hemophilia, etc. 

Question. What is a chronic disease?
Ans : A disease which lasts for many years is called chronic disease. Some of the chronic diseases may last for the entire life. A chronic disease often results in debility. Example : Arthritis, tuberculosis, diabetes, hypertension, etc.

Question. What are the different means by which infectious diseases are spread?
Ans : Means of spread of diseases is called Epidemiology. Air-borne diseases
(i) These diseases spread through air.
(ii) While sneezing or coughing, the droplets released in the air is inhaled by healthy person and the infection spreads.
(iii) E.g. TB, Common cold, Pneumonia, etc. Water-borne diseases These diseases spread through contaminated water. Sexually transmitted/physical contact diseases (STDs)
(i) These diseases spread by sexual contact from infected partner to the healthy.
(ii) E.g. AIDS, Syphilis, Gonorrhea, etc. Vector-borne diseases
(i) Vectors are intermediate carriers of infections.
(ii) E.g. Female Anopheles mosquito is a vector for malaria parasite, plasmodium.

Question. What are the conditions favouring air-bone diseases?
Ans : Conditions favouring air-borne infections :
(a) Close proximity to the infected person.
(b) Over-crowding
(c) Poor-ventilation

Question. Explain the following statements :
(a) Being disease free, is not the same as being healthy.
(b) Community health is essential for good individual health.
(c) Villagers suffer with cholera more than urban people.
Ans : (a) Being disease free is not the same as being healthy because health means a state of physical, mental and social well-being. One should also be mentally and socially well to have a good health.
(b) Health of all organisms depend on their environment. So public cleanliness and good social environment are necessary for good individual health.
(c) Cholera is a water-borne disease, i.e., it spreads by contaminated water. Villagers suffer with cholera more than the urban people in the absence of pure drinking water.

Question 1: State any two conditions essential for good health.

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.

Question. Which Vaccine was discovered for the first time and who discovered it?
Ans : Edward Jenner invented the vaccine for the first time and it was of smallpox.

Question. Why is making of anti-viral drugs more difficult than making anti-bacterial medicines?
Ans : Because viruses have very few biochemical mechanism of their own.

Question. State the principle of immunization.
Ans : Immune system responds against infectious microbes after detecting it first time. If this microbe again enter in body, immune system respond vigorously. This eliminate the infection more quickly than the first time. This is the principle of immunization.