NCERT Exemplar Problems Class 9 Science – Why Do We Fall III

Question 1:
Which one of the following is not a viral disease?
(a) Dengue (b) AIDS (c) Typhoid (d) Influenza
Answer:
(c) Typhoid fever is also known as typhoid. It is a common worldwide bacterial disease transmitted by the ingestion of food or water contaminated with the faeces of an infected person.
Dengue fever is also known as breakbone fever. It is a mosquito-borne tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles.
Human Immunodeficiency Virus infection/Acquired Immunodeficiency Syndrome
(HIV/AIDS) is a disease of the human immune system caused by infection with Human Immunodeficiency Virus (HIV).
Influenza, commonly known as ‘the flu’, is an infectious disease of mammals caused by RNA viruses. The most common symptoms are chills, fever, runny nose, sore throat, muscle pains, headache (often severe), coughing, weakness fatigue and general discomfort.

Question 2:
Which one of the following is not a bacterial disease?
(a) Cholera (b) Tuberculosis (c) Anthrax (d) Influenza
Answer:
(d) Influenza is a viral disease caused by myxovirus influenza.
Cholera is an infection of the small intestine caused by the bacterium Vibrio cholerae. The main symptoms of cholera are watery diarrhoea and vomiting. This may result in dehydration and in severe cases it results in grayish-blue skin.
Tuberculosis caused by various strain of Mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis typically attacks the lungs, but can also affect other parts of the body. It is spread through the air when people who have its infection cough, sneeze, and transmit respiratory fluids through the air.
Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lathal, and it affects both humans and animals. There are now effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment for influenza to refer Q. 1.

Question 3:
Which one of the following disease is not transmitted by mosquito?
(a) Brain fever (b) Malaria
(c) Typhoid (d) Dengue
Answer:
(c) Typhoid is a bacterial disease caused by Salmonela typhii. It is a food and water borne disease and it not transmitted by mosquito.
Brain fever, malaria and dengue all of them are communicable disease and are spread by vectors. Mosquito Anopheles transmits malaria, Cu/ex transmits filariasis and Aedes transmits dengue.

Question 4:
Which one of the following disease is not caused by bacteria?
(a) Typhoid (b) Anthrax
(c) Tuberculosis (d) Malaria
Answer:
(d) Malaria is a mosquito borne infections disease caused by Plasmodium (a protozoan).
It is characterised by periodic attacks of shivering followed by high fever, headache and muscular pains. Anaemia and enlarged spleen are other symptoms.
(Also, refer to Q. 1 and 0.2)

Question 5:
Which one of the following disease is caused by protozoans?
(a) Malaria (b) Influenza
(c) AIDS (d) Cholera
Answer:
(a) Malaria is caused by a protozoan Plasmodium. Influenza is caused by RNA virus, AIDS is caused by HIV and cholera is caused by bacterium Vibrio cholerae.

Question 6:
Which of the following has long term effect on the health of an individual?
(a) Common cold (b) Chickenpox
(c) Chewing tobacco (d) Stress
Answer:
(c) Chewing tobacco may cause long term effects on an individuals. It increases the risk for leukoplakia which is a precursor to oral cancer. Chewing tobacco has been known to cause cancer, particularly of mouth and throat.

Question 7:
Which of the following can make you ill if you come in contact with an infected person?
(a) High blood pressure (b) Genetic abnormalities
(c) Sneezing (d) Blood cancer
Answer:
(c) The transmission of microbes occurs through the little droplets, sneezed out by an infected person. A person in close vicinity of such an infected person can inhale these disease causing microbes and may become infected.

Question 8:
AIDS cannot be transmitted by
(a) sexual contact (b) hugs
(c) breast feeding (d) blood transfusion
Answer:
(b) Acquired Immunodeficiency Syndrome (AIDS) is caused by the human immunodeficiency virus, or HIV. HIV gradually reduces the efficiency of the human immune system, i.e., it destroys the body’s ability to fight disease. This makes the body vulnerable to other life-threatening diseases that finally cause the patient’s death. The options (a), (c) and
(d) shows the mode of transmission of AIDS virus.
HIV is transmitted through blood, semen and breast milk. Thus, a person can get infected with HIV by transfusion of infected blood, sharing of needle with an infected person or having sexual intercourse with an infected person. An unborn child can get the infection from the mother or a mother’s milk can infect an infant.
HIV is not spread by touching an infected person, nor can it be spread by breathing in the virus when the patient coughs or sneezes.
The common symptoms of AIDS are swollen lymph glands, weight loss, frequent fever, night sweats and diarrhoea. The disease may effect the central nervous system, which may cause memory loss and difficulty in speaking.
No drug has yet been developed to cure AIDS. A patient is usually given a combination of drugs that manage to slow down the progress of the disease.
To prevent HIV infection, we should follow the safe practices given below
(i) We should make sure that the blood used in transfusion for our family members or us has been screened for HIV. Blood banks and hospitals should test potential blood donors for HIV.
(ii) Disposable needles and syringes should be used.
(iii) One should not share shaving blades or razors.
(iv) One should not have multiple sex partners. Condoms can be used to prevent the transmission through HIV sexual fluids.

Question 9:
Making anti-viral drugs is more difficult than making anti-bacterial medicines because
(i) viruses make use of host machinery
(ii) viruses are on the border line of living and non-living
(iii) viruses have very few biochemical mechanisms of their own
(iv) viruses have a protein coat
Answer:
(a) Designing safe and effective antiviral drug is difficult because viruses use the host’s cell to replicate. This makes it difficult to find the exact targets where the drug can interfere with the virus without harming the host organism.

Question 10:
Which one of the following causes kala-azar?
(a) Ascaris (b) Trypanosoma
(c) Leishmania (d) Bacteria
Answer:
(c) Leishmania a protozoa causes kala-azar or black fever signs and symptoms include, fever, weight loss, fatigue, anaemia and swelling of liver and spleen.

Question 11:
If you live in a over crowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases?
(a) Cancer (b) AIDS
(c) Air borne diseases (d) Cholera
Answer:
(c) In closed areas, the droplets nuclei recirculate and pose a risk to everybody. Thus, over crowded and poorly ventilated houses is a major factor in spread of air borne diseases.

Question 12:
Which disease is not transmitted by mosquitoes?
(a) Dengue (b) Malaria
(c) Brain fever or encephalitis (d) Pneumonia
Answer:
(d) Pneumonia is an inflammatory condition of lung affecting the lung alveoli. It is caused by a virus or bacteria. Symptoms include cough chest pain, fever and difficulty in breathing. Pneumonia is an air borne disease whereas dengue, malaria and brain fever are vector (mosquito) borne diseases.

Question 13:
Which one of the following is not important for individual health?
(a) Living in clean space
(b) Good economic condition
(c) Social equality and harmony
(d) Living in a large and well furnished house
Answer:
(a) The conditions essential for good health are clean surrounding
(i) Availability of clean drinking water.
(ii) Availability of clean adequate, nutritious food.
(iii) Social equality and harmony.

Question 14:
Choose the wrong statement.
(a) High blood pressure is caused by excessive weight and lack of exercise.
(b) Cancers can be caused by genetic abnormalities
(c) Peptic ulcers are caused by eating acidic food
(d) Acne in not caused by staphylococci
Answer:
(d) Acne is a common human skin disease characterised by areas of seborrhea and pimples.
Propionibacterium acnes is the anaerobic bacterium that causes acne. It is not caused by staphylococci.

Question 15:
We should not allow mosquitoes to breed in our surroundings because they
(a) multiply very fast and cause pollution
(b) are vectors for many diseases
(c) bite and cause skin diseases
(d) are not important insects
Answer:
(b) Many animals which live with us carry disease. These animals transfers infecting agents from sick person to another potential host (healthy person) and act as vectors. Mosquitoes are known to cause many diseases.

Question 16:
You are aware of Polio Eradication Programme in your city. Children are vaccinated because
(a) vaccination kills the polio causing microorganisms
(b) prevents the entry of polio causing organism
(c) it creates immunity in the body
(d) All of the above
Answer:
(c) Children are vaccinated by the vaccine to improves immunity to a particular disease, it contains an agent that resembles a disease causing microorganism and are made from weakened or killed microbe.
The pulse polio programme is an immunization drive against polio. Polio is a disease of the muscles and nerves which can even cause paralysis. To prevent this disease, oral vaccines are given periodically to all children under 5 years of age in our country.

Question 17:
Viruses, which cause Hepatitis, are not transmitted through
(a) air (b) water (c) food (d) personal contact
Answer:
(a) Hepatitis is a disease in which the liver becomes enlarged. The symptom of the disease is the yellowing of the skin and the whites of the eyes, as condition referred to a jaundice. The yellowing is because of the presence of excessive bilirubin (a bile pigment) in the blood.
Viral hepatitis is caused by different strains of the hepatitis virus and the hepatitis caused is named after it. Thus we have, hepatitis. A to hepatitis-G, named after the strains A, B, C, D, E, F and G. Some of these strains (e.g., hepatitis-A) get transmitted through contaminated food or water. Other, (e.g., hepatitis-B) get transmitted through blood, semen, saliva and breast milk.

Question 18:
Vectors can be defined as
(a) animals carry the infecting agents from sick person to another healthy person
(b) microorganisms which cause many diseases
(c) infected person
(d) diseased plants
Answer:
(a) Vectors or intermediaries are animals insects that carry the infecting agents from a sick person to another healthy person. Mosquitoes (for malaria, filariasis, yellow fever and dengue), flies (typhoid, kala-azar, sleeping sickness), louse (typhus) and rat (for plague).

Short Answer Type Questions

Question 19:
Give two examples for each of the following.
(a) Acute disease (b) Chronic diseases
(c) Infectious diseases (d) Non-infectious diseases
Answer:
(a) Acute disease cast for short period of time and do not cause long term effect, e.g., cold and cough.
(b) Chronic disease last for long time even for lifetime and cause long term effects on human health.
e.g., tuberculosis and arthritis.
(c) Infectious diseases are caused by attack of pathogens and can pass from one person to another.
e.g.,malaria and chickenpox.
(d) Non-infectious diseases are caused by factors other than living pathogens and are not transmitted.
e.g., diabetes and goitre.

Question 20:
Name two diseases caused by protozoans. What are their causal organisms?
Answer:
Two disease caused by protozoans are malaria caused by Plasmodium. Amoebic dysentery caused by Entamoeba histolytica.

Question 21:
Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?
Answer:
Peptic ulcers is caused by Helicobacter pylori, previously named as Compylobacter pylori is a Gram negative bacteria found in stomach. It was identified in 1982 by Australian scientist Barry Marshall and Reborn Warren.

Question 22:
What is an antibiotic? Give two examples.
Answer:
Antibiotics are the drugs that are used to cure diseases caused by bacteria.There are different kinds of antibiotics which attack different processes and structures in bacteria to kill them or to stop their growth.
First type of antibiotic stops the production of a compound needed for the growth of the cell wall of bacteria. This prevents the cell wall from expanding when the other parts of the cell are growing. As a result, the cell bursts, which kills the bacteria, Penicillin, an important antibiotic, works in this way for streptococal infections.
Other types of antibiotics work by interfering in other processes such as the production of proteins, e.g., streptomycin for tuberculosis.

Question 23:
Fill in the blanks.
(a) Pneumonia is an example of……
(b) Many skin diseases are caused by….
(c) Antibiotics commonly block biochemical pathways important for the
growth of………
(d) Living organisms carrying the infecting agents ts from one person to
another are called……….
Answer:
(a) Pneumonia is an example of Infectious disease. (Also, refer to G. 19)
(b) Many skin diseases are caused by
(c) Antibiotics commonly block biochemical pathways important for the growth of cell wall. (Also, refer to 22)
(d) Living organisms carrying the infecting agents from one person to another are called Vectors . (Also, refer to Q. 18)

Question 24:
Name the target organs for the following diseases
(a) Hepatitis targets………..
(b) Fits or unconsciousness targets……..
(c) Pneumonia targets…….
(d) Fungal disease targets……..
Answer:
(a) Hepatitis targets liver (Also, refer to Q. 17)
(b) Fits or seizure targets brain.
It is caused by a disturbance in electrical activity of the brain which can be due to conditions such as epilepsy. In serious cases patient may lose consciousness or experience conclusions.
(c) Pneumonia targets lung. (Also, refer to Q. 12)
(d) Fungal disease targets skins.

Question 25:
Who discovered ‘vaccine’ for the first time?
Name two diseases which can be prevented by using vaccines.
Answer:
A ‘vaccine’ is a biological preparation that improves immunity to a particular disease. Vaccine can be prophylactic or the apeutic.
An English physician, Edward Jenner (1749-1823) observed that people who suffered cowpox (a mild disease) did not acquire smallpox, (a more severe disease). Jenner decided to test his observations about cowpox and smallpox.
He took some pus with a sterile needle from the cowpox rashes of an infected girl and injected it into scratches made in the skin of an uninfected boy, who soon got cowpox. After he recovered, Jenner injected the boy’s arm with pus from the spots of a person suffering from smallpox. Luckily, the body did not get smallpox and Jenner’s experiment was successful.
Thus, Jenner made the first vaccine against smallpox using the microbes of cowpox, a similar but less severe disease. The modern term ‘vaccination’ comes from the Latin words vacca which means cow and vaccinia meaning cowpox.
The second generation of vaccines was introduced in 1880s by Louis Pasteur who developed vaccines for chicken pox, cholera and anthrax.

Question 26:
Fill in the blanks.
(a) ……. disease continues for many days and causes … on body.
(b) …………….disease continue for a few days and causes no longer term
effect on body.
(c) is defined as physical, mental and social well-being and
comfort.
(d) Common cold is……
(e) Many skin diseases are caused by……
Answer:
(a) Chronic disease continues for many days and causes long term effects on the body. e.g., include elephantiasis, cardiovascular diseases, tuberculosis, diabetes, arthritis cancer etc.
(b) Acute diseases continues for a few days and causes no longer term effect on body, e.g., Indude cold, cough, typhoid, cholera, etc.
(c) Health is defined as physical, mental and social well-being and comfort.
Being healthy means one feels good physically, has positive outlook and is able to cope with the social and mental pressures without much difficulty.
(d) Common cold is acute desease.
(e) Many skin diseases are cased by fungi g., Athlete’s foots, ringworm etc.

Question 27:
Classify the following diseases as infections or non-infectious.
(a) AIDS (b) Tuberculosis
(c) Cholera (d) High blood pressure
(e) Heart disease (f) Pneumonia
(g) Cancer
Answer:
Difference between infectious and non-infectious disease are

Question 28:
Name any two groups of microorganisms from which antibiotics could be extracted.
Answer:
Fungi (Penicillium notatum) and Bacteria (Streptomyces cerevisae). {Also, refer to Q. 22)

Question 29:
Name any three disease transmitted through vectors.
Answer:
Disease caused by vectors are (Also, referto 0. 18)

Long Answer Type Questions

Question 30:
Explain giving reasons
(a) Balanced diet is necessary for maintaining healthy body.
(b) Health of an organism depends upon the surrounding environmental conditions.
(c) Our surrounding area should be free of stagnant water.
(d) Social harmony and good economic conditions are necessary for good health.
Answer:
(a) A balanced diet is the first and foremost condition necessary for good health. A balanced diet provides all the nutrients e.g., proteins, carbohydrates, fats, vitamins and minerals required by the body in correct proportions. When our diet lacks one or more of these nutrients, we get deficiency diseases or nutritional disorders.
Excessive or inadequate intake of food and nutrients leads to condition such as obesity, kwarshikor and rickets. If our diet, lacks the mineral iron, we may get a disease called anaemia.
Abnormal intake of nutrients and minerals such as vitamin-A which causes hypervitaminosis-A and calcium which causes rickets. A balanced diet prevents deficiency diseases. It also increases our ability to fight aganist infections in general.
(b) Our health depends on the cleanliness of our surroundings. Flies and mosquitoes carry germs that cause diseases, Flies breed in rotting garbage and mosquitoes breed in pools of stagnant water.
So, people fall ill quite often if the area in which they live or work has uncleaned garbage, pools of stagnant water or open drains. Clean air is also a part of our surrounding and a basic requirement for good health.
(c) Refer to part (b)of Q.
(d) Human beings live in societies. Our social environment therefore plays an important part in our individual health. We live in villages, town or cities, our physical environment is decided by our social environment.
e.g., if there is not agency to ensure that garbage is collected and disposed and no one takes responsibility for cleaning the drains, to ensure that waste water does not get collected in the streets or open spaces, there will be heaps of garbage and trash littered here and there, will be open drain water lying stagnant around where we live.
Therefore, the possibility of poor health will increase. So, public cleanliness is also and important contribution to an individual’s health.

Question 31:
What is a disease? How many types of diseases have you studied? Give examples.
Answer:
Human health gets negatively affected due to physiological malfunctioning, psychological reasons or pathogenic organisms. The term disease means without ease or comfort. Disease can be defined as an impairment (malfunctioning) of the normal state of the living organism that disturbs or modifies the performance of the vital organs and hampers their function. Disease may be a response to
(i) Environmental factors (as malnutrition, industrial hazards or climate).
(ii) Specific infective agents (as worms, protozoans, fungi, bacteria or viruses).
(iii) Inherent defects of the organism (as genetic anomalies).
(iv) Combination of these factors. (Also, refer to Q. 19)

Question 32:
What do you mean by disease symptoms? Explain giving two examples?
Answer:
Symptoms are the evidences that point to the presence of a-disease they are visible in the form of either structural or functional changes in our body or any of its parts. On the basis of these symptoms doctors search for definite clues or sings for a particular disease, e.g., The symptoms for malaria and typhoid are same like fever, weakness, headache etc. but signs for the disease are different as malaria fever manifests through chills and that of typhoid fever are rashes, stomach pain etc.
A simple blood test (CBC) is enough to detect malarial infection and for typhoid widal test is conducted.

Question 33:
Why is immune system essential for our health?
Answer:
The human immune system consist of lymphoid organs, tissue cells and antibodies. The immune system recognises foreign antigens and generates an immune response and remembers them.
An immune response is the way in which the human body responds to invasion of specific pathogens or antigens. These response involve the production of cells (lymphocytes) and chemicals (antibodies), that are designed to defend the body against the pathogens. Antigens are substances that can activate an immune response. Antigens trigger the production of antibodies (glycoproteins or immunoglobulins) by the immune system. Each type of antibody is specific to a particular antigen and reacts with it to render it harmless.

Question 34:
What precautions will you take to justify “prevention is better than cure”?
Answer:
When someone gets a disease
(i) his or her body function gets damaged and may never recover completely.
(ii) he or she may become bedridden of sometime.
(iii) he or she can serve as a medium for further spread of disease Therefore prevention is better than cure.
Ways of prevention of infectious diseases, Public hygiene is the key to the prevention of infectious diseases. For prevention of diseases, following general practices are adopted
(i) Avoid exposure to air-borne microbes.
(ii) Adopt living condition that are not overcrowded.
(iii) Prevent exposure to water-borne microbes.
(iv) Safe drinking water should be provided.
(v) Avoid vector-borne infection, and establish clean environment as it would not allow mosquito breeding.

Question 35:
Why do some children fall ill more frequently than others living in the same locality?
Answer:
Some children fall ill more frequently than other living in the same area due to their weak immunity, or slow immune response. (Also, refer Q. 33)

Question 36:
Why are antibiotics not effective for viral disease?
Answer:
Antibiotics are not effective for viral diseases as the virus uses the host organisms machinery to grow and divide. Therefore, it becomes difficult to aim the virus without affecting the host. (Also, refer to Q. 22 and Q. 9)

Question 37:
Becoming exposed to or infected with an infectious microbe does not necessarily mean developing noticeable disease. Explain.
Answer:
The strong immune system of a healthy person normally fights of microbes. The body has specialised cells to kill the pathogenic microbes. These cells are active when infectius microbes enter the body and if they are successful in removing the pathogen, we remain disease-free.
So, even exposure to infectious microbes may not cause disease to a person having strong immune system.
(Also, refer to Q. 33)

Question 38:
Give any four factors necessary for a healthy person.
Answer:
For factors necessary for a healthy person are
(i) Balanced diet
(ii) Clean surrounding environment
(iii) Social harmony
(iv) Good economic conditions (Also, refer to 30)

Question 39:
Why is AIDS considered to be a ‘Syndrome’ and not a disease?
Answer:
AIDS stands for Acquired Immune Deficiency Syndrome. It is caused by the Human immunodeficiency Virus or HIV. A person can be infected with HIV but not acquire AIDS. It is designated as a syndrome and not a disease as a group of health problems are its characteristic AIDS causes individuals to become susceptible to bacterial, viral, fungal, and parasitic infections. Individuals also exhibit increased rates of cancers like lymphomas.
Technically, a syndrome can be defined as a group of symptoms that are characteristic of a disorder or disease (but it may be due to multiple diseases or no disease, e.g., an accident). A disease however is a disorder of a specific organ or body system that arises from heredity, infection, environmental causes, etc.