CBSE Class 9 Science Why Do We Fall ill Worksheet Set A

Question : What is health?
Answer : Health is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.

Question : What is disease?
Answer : A disease is an abnormal condition of the body which does not let the body function properly.

Question : What do you mean by symptoms and signs of a disease?
Answer : A symptom is a change in normal functioning of the body which felt by a patient, but which cannot be observed by the doctor. For example- stomach ache, sore throat and nausea are symptoms. A sign of a disease is a change in the bodily function that can be observed. For example- yellow eye and skin can be due to a disease called hepatitis.

Question : State any two condition essential for good health.
Answer : Two conditions essential for good health are: State of physical, mental and social well-being . Better surroundings or environment.

Question : State any two conditions essential for being free of disease.
Answer : The two conditions essential for being free of disease are: (1) Personal and domestic hygiene. (2) Clean environment and surroundings.

Question : What is Infection and Infectious Disease?
Answer : The entry and multiplication of a pathogen or microbe into the body is called infection and the disease caused by them is called infectious disease.

Question : What are the different means by which infectious diseases are spread?
Answer : Infection causing microbes travel from patient to another person through.
(a) Air: sneezing or cough through little droplets in air which reach to another person, e.g. common cold
(b) Water: Contaminated water carries disease-causing microbes which cause infection of certain diseases e.g. cholera.
(c) Sexual contact: Diseases such as syphilis or AIDS are transmitted by sexual contact from one partner to other.
(d) Animals: These are intermediaries called vectors that host e.g. female anopheles mosquito causes malaria.

Question : Classify infectious agents into different categories and also mention the diseases caused by them.
Answer : The different categories of infectious agent along with the diseases which they caused are
Infectious Agents Diseases cause
1. Bacteria Tuberculosis, Cholera, Typhoid….
2. Viruses Mumps, Common cold, Rabies
3. Fungi Ringworm, Athlete’s foot,
4. Protozoa Malaria, Dysentery ,Kala azar
5. Worms Filariasis , Ascariasis

Question : Differentiate between vector and carrier?
Answer : Carrier is an individual which has the diseases, it is capable of transmitting the disease to a new individual.
Example: A human with HIV, can transmit the virus to another healthy individual is an example of carrier.
Vector is an organism which is capable of transmitting disease from infected individual to new individual without having the disease.
Example Anopheles mosquito that carries malaria parasites between humans is an example of vector.

Question : What is inflammation?
Answer : The defensive reaction of the body’s immune system in response to infection or injury is called inflammation. Inflammation is characterized by swelling, reddening, pain in the affected area of the body, plus an increase in body temperature.

Question : The signs and systems of a disease depend on the tissue or organ which the microbes targets. Explain with examples.
Answer : In case of tuberculosis, lungs are affected and hence the symptoms are cough and breathlessness. In case of jaundice, liver is targeted and hence the symptoms are loss of appetite and yellow urine.

Question :`Public cleanliness is important for individual health.’ Comment.
Answer : Public cleanliness is important for individual health because diseases may spread in the community, thus affecting individual health. Garbage thrown in open spaces, overflowing drains and accumulation of stagnant water etc. cause spread of disease. These are places where disesase causing microbes multiply, mosquitoes and flies breed.

Question : What are the two ways to treat an infectious disease?
Answer : The two ways to treat an infectious disease are-
a. To reduce the effects of the disease.
b. To kill the cause of the disease.

Question :What is the basis of the principle of immunization?
Answer : When the immune system first notices an infectious microbe, it responds against it. When the particular microbes enter the body for the next time, the immune system responds with even greater viguor. This eliminates the infection more quickly than the first time. This is the basis of the principle of immunization.

Question :What is an antibiotic? Give it’s example
Answer : Antibiotic is a chemical substance produced by living organisms such as bacteria, fungi etc. which can kill or stop the growth of some pathogenic microorganisms example- streptomycin

Question : Explain why antibiotics do not work against viruses but work against many groups of bacteria.
Answer : Antibiotics block the bacterial process that build cell wall in bacteria. As a result, the growing bacteria become unable to make cell wall and die easily. But viruses do not have their own pathways and hence antibiotics do not work against virus.

Question : What precaution will you take to justify “prevention is better than cure ”?
Answer : when someone gets a disease
His or her body function gets damaged and may never recover completely.
i. He or she may become bedridden of something.
ii. He or she serve as a medium for further spread of disease.
iii. Therefore prevention is better than cure.
Following precautions should be taken for prevention of disease:
a. Maintaining hygienic conditions.
b. Awareness about the disease and causal organism.
c. Proper nutrition with balanced diet, clean food and water.
d. Regular medical check up.
e. Regular exercise and relaxation.

Question : What is the importance of vaccination?
Answer : The importance of vaccination is that it helps a person to acquire immunity against a certain disease. Vaccination protects us from disease like small pox, rabies, polio, diphtheria, and chicken pox.

Question :Why is AIDS considered to be a `Syndrome and not a disease’ ?
Answer : AIDS is considered a syndrome and not a disease because AIDS causing virus-HIV comes into the body via the sexual organs or any other means like blood transfusion and spread to lymph nodes all over the body and the body can no longer fight off even minor infections .Instead, every small cold can become pneumonia, or minor gut infection can become serve diarrhea. The effect of disease becomes very serve and complex, at times killing the person suffering from AIDS. Hence, there is no specific diseases symptoms for AIDS but it results in a complex disease and symptoms.

Question :Name the protozoans that cause:
a. Sleeping sickness b. Kala-azar
Answer : a. Trypanosoma causes sleeping sickness
b. Leis mania causes Kala-azar

Question : Against which disease BCG vaccine is employed?
Answer : Tuberculosis

Question :How can the functioning of immune against a disease?
Answer : By providing proper and sufficient nourishment and food.

Question : Why are we normally advised to take bland and nourishing food when we are sick?
Answer : We are normally advised to take bland and nourishing food when we are sick in order to improve our immune system, which will help us to fight against disease.

Question : Write the symptoms and disease associated with the following:
a. When the microbes attacks the lungs.
b. When the virus enters the liver.
Answer : (a.) The symptoms are cough, fever, chest pain and the disease associated can be Tuberculosis.
(b) The symptoms are headache, high fever, loss of appetite, nausea and the disease can be Jaundice.

HOME ASSIGNMENT-
Question : Difference between:-
a. Differentiate between Acute and Chronic diseases.
b. Congenital and acquired diseases
c. Infectious and non-infectious disease

Question : Classify the following as infectious or non-infectious
a. AIDS b. Tuberculosis
c. Cholera d. High blood pressure
e. pneumonia f. Cancer

Question : Give reasons-
a. Balanced diet is necessary for maintaining healthy body.
b. Health of an organism depends upon the surrounding environmental conditions.

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