Important Questions for CBSE Class 9 Science Chapter 13 Why Do We Fall III
Question. 1 Name any two groups of microorganisms from which antibiotics could be extracted.
Answer. Bacteria and fungi. Harmful Effects of Microorganisms
Question.2 Why are we advised to take blend and nourishing food when we are sick ?
Answer. We are advised to take blend and nourishing food so that scarcity (loss) of nutrients caused during sickness get fulfilled.
Question.3 What is the purpose of vaccination ?
Answer. The purpose of vaccination is to induce the production of specific antibodies to confer immunity against subsequent infection.
Question.4 Many vaccines form the public health programme of childhood immunisation for preventing infectious disease. Name any two such diseases.
(i) Vaccine against measles.
(ii) BCG vaccine against T.B.
Question.5 Majority of children in many parts of India are already immune to Hepatitis A by the time they are five years old. Why ?
Answer. This is because since beginning they are exposed to the virus through water.
Question.6 Name any two diseases which are caused due to unprotected sexual intercourse.
Answer. (i) AIDS (ii) Syphilis.
2- MARKS QUESTIONS
Question.1 Give two examples for each of the following :
(a) Acute diseases
(b) Chronic diseases
(c) Infectious diseases
(d) Non-infectious diseases.
(a) Viral fever, Flu
(b) Elephantiasis, Tuberculosis (TB)
(c) Smallpox, Chickenpox
(d) Diabetes, Goitre
Question.2 Name two diseases caused by Protozoans. What are their causal organisms ?
(i) Sleeping sickness caused by Trypanosoma, Malaria by Plasmodium.
(ii) Kala-azar caused by Leishmania.
(i) Which bacterium causes peptic ulcers ?
(ii) Who discovered the above pathogen for the first time ?
(i) Helicobactor pylori
(ii)Marshall and Warren.
Question.4 What is an antibiotic ? Give two examples.
Answer. Antibiotic is a chemical substance that kills bacteria, secreted by microorganisms which can kill the pathogens. Examples, Penicillin and Streptomycin.
Question. 5 Name any four diseases transmitted through vectors.
Answer. Malaria, Dengue, Kala-azar and Plague.
Question.6 List any four essential factors that must be taken icare of by an individual for keeping good health.
(i) Balanced diet. (ii) Disease free environment.
(iii) Proper sanitation. (iv) Mental and social stability.
Question.7 Which amongst the two diseases : acute or chronic has adverse effect on the health of a person? Explain giving a suitable example.
Answer.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.8 What do signs and symptoms indicate if a person is suffering from any disease ? [SAII -2014]
Answer.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.9 Give four modes of transmission of AIDS.
- Blood to blood contact (transfusion).
- From an infected mother to her unborn baby during pregnancy, labour or delivery.
- Through breast feeding.
(i) What is an epidemic disease ?
(ii) Which organ is affected if a person is suffering from jaundice ?
(i) An epidemic is the rapid and extensive spread of disease that affects many individuals simultaneously in a particular area. It is generally an infectious disease.
(ii)Liver is affected in jaundice.
Question.11 How can we prevent water borne and vector borne infections ?
- Water borne infections can be prevented by providing safe drinking water.
- Vector borne infections can be prevented by providing clean environment.
Question.12 Name the pathogens which can cause acne and sleeping sickness. [SAII -2014]
Answer. Acne — Staphylococci
Sleeping sickness — Trypanosoma.
Question.13 . What causes Japanese encephalitis ? How it can be prevented ?
- Japanese encephalitis is caused by virus which enters into human body through mosquito bite.
- By keeping the surrounding clean and taking proper measures against mosquito bite, it can be prevented.
Question.14 What is an antibiotic ? Give its one example.
Answer. Antibiotic is a chemical substance secreted by microorganisms which can kill the pathogens. Example : Penicillin.
Question.15 State any two conditions essential for good health. [SAII-2014]
Answer. Health is a state of being well enough to function well physically, mentally and socially. The health of any individual depends upon :
- Better social environment.
- Better public cleanliness.
- Good economic conditions.
- Social equality and harmony.
Question.16 State any two conditions essential for being free of disease.
Answer. The conditions essential for being free of disease are :
- Eating good food (balanced diet).
- Maintaining personal and public hygiene.
- Clean surroundings.
Question.17 Why are we normally advised, to take bland and nourishing food when we are sick ? [SAII – 2011, 2013]
Answer. When a person is sick, then his normal body functions get disturbed. In such a situation, such food is required which is easy to digest and contains adequate nutrients for the speedy recovery. Thus, bland and nourishing food is required during sickness.
Question.18 Under which of the following conditions are you most likely to fall sick ?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles. Why ?
Answer. l am most likely to fall sick when I am near to my friend who is suffering from measles. Since measles is an acute infectious disease caused by a virus. This disease is characterized by fever and a blotchy rash. This means that one should stay away from a person suffering from measles.
3 MARKS QUESTIONS
Question. 1 Differentiate between acute diseases and chronic diseases.
Question.2 The signs and symptoms of a disease will depend on the tissue or organ which the microbe targets Justify the statement with two examples. [SAll – 2014]
Answer. Every microorganism shows its effect on any particular tissue or organ after entering into the body. Thus, there is a change in the structure and function of that tissue or organ. For example, if the lungs are the targets, the symptoms will be cough and breathlessness. If the liver is the target, there will be jaundice. This is called Organ specific manifestation.
(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 ? [SAII – 2014]
(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) (a) Stagnant water in the surroundings, (b) Accomulation of garbage.
(iii) Because Female Anopheles mosquitoes require large amount of proteins to lay their eggs
Question.4 What is inflammation ? Write the symptoms of this in human body.
Answer.In human body, when there is an infection, an active immune system recruits many cells to the affected tissue to kill the disease-causing microbes. This recruitment process is called inflammation. Symptoms : (i) Swelling and pain, (ii) Fever.
(i) What are the various ways to prevent the diseases ?
(ii) What is immunisation ?
(i) We can prevent disease in two ways :
(a) General ways: By preventing exposure to infectious microbes.
- By providing safe drinking water and public hygiene.
- By providing proper and balanced diet, (any two)
(b) Specific ways : By immunisation.
(ii)Immunisation : The process of developing immune power in the body to fight against the diseases is called immunisation. In the process of immunisation, a vaccine is introduced into the body doe to which the immune power of the body improves.
Question.6 State two principles of treatment of a disease.
Answer. There are two ways to treat an infectious disease :
(i) By reducing the effect of the disease
(a) By symptomatic treatment. (b) By taking a bed rest
(ii) By killing the microorganisms that act as infectious agents.
Question.7 List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor ? Why or why not ?
Answer. When there is a disease, either the functioning or the appearance of one or more systems of the body will change for the worse. These changes give rise to symptoms and signs of disease. Symptoms of disease indicate that a person is not well. These symptoms can be in the form of headache, cough, loose motions or wound with pus. These symptoms indicate that there-may be a disease but they do not indicate what the disease is. Therefore, even if you have any of these symptoms, it is advisable to go to the doctor because only he can diagnose about any signs of a disease on the basis of these symptoms. These signs will give a little more definite indication of the presence of a particular disease. But if there is only one symptom of headache, then there is no need of visiting a doctor because it could be due to Tiredness or Stress.
Question.8 In which of the following case do you think the long-term effects on your health are likely to be most unpleasant ?
- if you get jaundice ?
- if you get lice ?
- if you get acne. Why ?
Answer. Having lice and acne will not have long lasting effects on our body. But if you get jaundice, it will have drastic long-term effect You will show symptoms such as :
- High temperature, headache and joint pains.
- Loss of appetite with a feeling of nausea and vomiting.
- Irritating rashes.
You will have prolonged general poor health which require complete bed rest for earlier recovery.
Question.9 What are the different means by which infectious diseases are spread ? [SAII – 2011, 2013]
Answer. The various means by which the infectious diseases get spread are :
- Through air : This occurs through the little droplets thrown out by an infected person who sneezes or coughs. Someone standing closeby can breathe in these droplets and the microbes get a chance to start a new infection. Examples of such diseases which spread through the air are the common cold, pneumonia and tuberculosis.
- Through water: This occurs if the excreta from someone suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby.
The cholera-causing microbes will enter new hosts through the water they drink and cause disease in them. Such diseases are much more likely to spread in the absence of safe supplies of drinking water.
- Through sexual contact: Microbial diseases such as Syphilis or AIDS are transmitted by sexual contact from one partner to the other. Other than the sexual contact, the AIDS virus can also spread through blood-to-blood contact with infected people or from an infected mother to her baby during pregnancy or through breast feeding.
- Through vectors: There are certain animals which carry the infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are called vectors. The commonest vectors are the mosquitoes which spread malaria. In many species of mosquitoes, the females anopheles need highly nutritious food in the form of blood in order to be able to lay mature eggs:
Question.10 How many times did you fall ill in the last one year ? What were the illnesses ? (a) Think of one change you could make in your habits in order to avoid any/most of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any/most of the above illnesses.
Answer. I fell ill thrice in the last one year. At first time, I suffered from common cold, at second time I suffered from influenza (eye-flu) and at third time, I suffered from diarrhoea.
(a) The change which I brought in my habits to avoid any of this type of illness in near future is:
(i) To remain away from people suffering from common cold or eye-flu.
(ii) To clean hands before meals and to take purified drinking water.
(b) Availability of purified drinking water all the time throughout the year.
Question.11 A doctor/nurse/health-worker is exposed to more sick people than others in the community.
Find out how she/he avoids getting sick herself/himself.
Answer. A doctor/nurse/health-worker take the following precautions to avoid getting sick herself. He/She:
- always wear masks while diagnosing mouth or chest infections.
- always wear hand gloves even while doing minor surgeries.
- always clean hands as well as instruments after diagnosis of the patient.
- makes sure that they are immunized against all contagious diseases.
- takes balanced diet (especially rich in proteins) to build their powerful immune system.
- dispose of any sputum, blood sample, urine or stool, properly.
Question.12. Under which of the following conditions is a person most likely to fall sick ?
(a) When she is recovering from malaria.
(b) When she has recovered from malaria and is taking care of someone suffering from
(c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chickenpox. Why ?
Answer. A person is most likely to fall sick when she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chickenpox. There are following reasons for this :
- When a person gets a disease like malaria he has loss of appetite, vomiting and high fever. This leads to loss of body fluids and makes body very weak. Under such circumstances if she is on a four day fast, then her defense system will be totally weak and she can even collapse.
- With the weak immune system if she is taking care of someone suffering from chickenpox, then it is more likely that she may also get the disease.
Question.1 What precautions can you take in your school to reduce the incidence of infectious diseases ?
Answer. The following precautions can be taken in any school to reduce the incidence of infectious diseases:
- Isolation of such students who suffer from common cold or eye-flu (to prevent the spreading of air-borne diseases).
- Availability of clean drinking water (to prevent the spreading of water-borne diseases).
- Clean surroundings which will not allow the growth and multiplication of vectors.
- Starting public health programme of childhood immunisation.
- Spreading knowledge through lectures and seminars about, how to prevent the spread of infectious diseases
(a) What is immunisation ?
(b) Define immunity and vaccination.
(c) Define vaccine. .
(d) What type of diseases can be prevented through vaccination ? [SAII -2013]
(a) Immunisation is a process of inoculation (injecting) of substance (vaccine) into a healthy person in order to develop immunity against the disease.
(b) Immunity is the ability of a body to recognise, destroy and eliminate external disease-causing agents. This immunisation is done by giving vaccine and thus it is also known as vaccination.
(c) The vaccine is a solution containing the disease-causing organisms in a diluted or weakened form. It may have organisms in living or even dead form.This does not actually cause the disease but this would prevent any subsequent exposure to the infecting microbe from turning into actual disease.
(d) Protection against diseases like smallpox, rabies, polio, diphtheria, chickenpox and hepatitis is provided through vaccination. It has been possible to eradicate smallpox from all regions of the world through a massive vaccination programme.
Question.3 Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Answer. After conducting a survey, I have found the following three most common diseases in my locality.
Place of study : Jalandhar (Punjab- India)
Question.4 A baby is not able to tell her / his caretakers that she / he is sick. What would help us to find out:
(a) that the baby is sick ?
(b) what is the sickness ?
(a) The following symptoms will help us to find out that the baby is sick :
(i) Repeated crying and not responding to any stimuli.
(ii) High body temperature.
(iii) Loose motions.
(iv)Drooping of eyes.
(v) Redness of eyes.
(b) The following signs will help us to find out what is the sickness :
(i) Yellowing of eyes, pale skin and passing of yellow urine indicate that baby is suffering from jaundice.
(ii) Redness in the eye and persistent rubbing of eyes indicate about eye-flu.
(iii) Gripping pain in the stomach, loose skin and repeated loose motions indicates about diarrhoea.
(iV) High fever, headache, nausea, muscular pains and feeling very cold and shivering indicates about malaria.
(v) If only fever is there with no other visible symptoms then laboratory tests are to be done which will reveal about the signs of any disease.
APPLICATION BASED QUESTIONS
Question.1 What do you mean by active and passive immunisation ? [SAll – 2015]
Answer. 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.2 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 :
Question.3 Give any four factors necessary for a healthy person.
Answer. For a healthy person it is necessary that:
(i) The surrounding environment should be clean. Air and water-borne diseases will not spread.
(ii) Personal hygiene prevents infectious diseases.
(iii) Proper, sufficient nourishment and food is necessary for good immune system of our body.
(iV) Immunisation against severe diseases.
Question.4 Why is AIDS considered to be a ‘Syndrome’ and not a disease ?
Answer. AIDS causing virus – HIV that comes into the body via the sexual organs or any other means like blood transfusion will spread to lymph nodes all over the body. The virus damages the immune system of the body and due to this the body can no longer fight off many minor infections. Instead, every small cold can become pneumonia or minor gut infection can become severe diarrhoea with blood loss. The effect of disease becomes very severe and complex, at times killing the person suffering from AIDS. Hence, there is no specific disease symptoms for AIDS but it results in a complex disease and symptoms. Therefore, it is known as a syndrome.
Question.5 Name the target organs for the following diseases :
(а) Hepatitis targets…………
(b) Fits or unconsciousness targets…………
(c) Pneumonia targets…………
(d) Fungal disease targets…………
Answer. (a) Liver (b) Brain (c) Lungs (d) Skin.
Question.6 Who discovered ‘vaccine’ for the first time ? Name two diseases which can be prevented by using vaccines.
Answer. Edward Jenner.
Example : Smallpox, Polio.
Question.7 Classify the following diseases as infectious or non-infectious :
(a) AIDS (b) Tuberculosis
(c) Cholera (d) High blood pressure
(e) Heart disease (f) Pneumonia
(a) Infectious (b) Infectious
(c) Infectious (d) Non-infectious
(e) Non-infectious (f) Infectious
Question.8 What is a disease ? How many types of diseases have you studied ? Give examples.
Answer. When the functioning or the appearance of one or more systems of the body change for the worse, the body is said to be diseased. The diseases can be — acute / chronic / infectious / non-infectious. Examples : Influenza, tuberculosis, pneumonia, cancer respectively.
Question.9 A child is suffering from fever but the doctor cannot immediately pinpoint the ailment on the basis of this one symptom. Explain why. Also mention another two such general symptoms.
Answer. It is because any one symptom does not specify what the disease really is. For example, a headache may just be due to an examination stress or due to meningitis or one of a dozen different diseases. Similarly, fever may be due to different reasons.
Question.10 Name the causal organism of AIDS. Why a person suffering from AIDS cannot fight even very minor infections ?
Answer. HIV is the causal organism of AIDS. This virus goes to the human immune system and damages its function. So the body can no longer fight off even very minor infections.
Question.11 Give the modes of transmission of each of the following diseases :
(i) Syphilis (ii) Tuberculosis (iii) Jaundice (iv) Japanese encephalitis [SAII -2012]
Question.12. What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area ?
Answer. The following immunisation programmes are available at the nearest health centre in our locality :
In our locality, diphtheria, pertussis, tetanus, polio, typhoid and measles are major health problems. In order to prevent these diseases, an expanded programme of immunisation is carried by the government of India which covers all these diseases and provide free vaccination in our locality.
Higher Order Thinking Skills (HOTS) Questions
Question.1 What do you mean by immune response ? , [SAII – 2014]
Answer. Immune response is the reaction of the body’s immune system to foreign cells or substances that cause disease or may even be potentially dangerous. This response involves the production
of cells (lymphocytes) and chemicals (antibodies) designed to defend the body against the pathogen.
Question.2 What are the differences between a virus and a bacteria ?
Question.3 What do you mean by disease symptoms ? Explain giving two examples.
Answer. When the functioning or the appearance of one-or more systems of the body will change for the worse, it gives certain abnormal signs of the disease. These visual changes in human beings are called symptoms. Symptoms give indication of the presence of a particular disease.
- Lesions on the skin are the symptoms of chickenpox.
- Cough is the symptom of lung infection.
Question.4 What precautions will you take to justify “prevention is better than cure” ?
Answer. Following precautions should be taken for prevention of disease:
- Maintaining hygienic conditions.
- Awareness about the disease and causal organism.
- Balanced diet.
- Regular medical check-up.
Question.5 “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 ?
Answer. 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.
Question.1 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.
(a) Food is necessary for the growth and development of the body. Balanced diet provides raw materials and energy in appropriate amount needed for the substances like protein, carbohydrates, fats, mineral etc. which in turn are essential for the proper growth and functioning of the healthy body.
(b) Health is a state of being well enough to function well physically, mentally and socially and these conditions depend upon the surrounding environmental conditions, e.g., if there is unhygienic conditions in surrounding area, it is likely we might get infected or diseased.
(c) This is so because many water-borne diseases and insect vectors flourish in stagnant water which cause diseases in human beings.
(d) Human beings live in societies and different localities like villages or cities, which determine the social and physical environment and hence both are to be kept in harmony. Public cleanliness is important for individual health. For better living conditions lot of money is required. We need good food for healthy body and for this we have to earn more. For the treatment of diseases also, one has to be in good economic condition.
Question.2 Why is immune system essential for our health ?
Answer. The immune system of our body is a kind of defence mechanism to fight against pathogenic microbes. It has cells that are specialized to kill infecting microbes and keep our body healthy.
Question.3 Becoming exposed to or infected with an infectious microbe (toes not necessarily mean developing noticeable disease. Explain.
Answer. Because of strong immune system our body is normally fighting off microbes. We have cells which are specialised to kill the pathogenic microbes. These cells are active when infecting microbes enter the body and if they are successful in removing the pathogen, we remain disease-free. So even if we are exposed to infectious microbes, it is not necessary that we suffer from diseases.
Question.4 Why do some children fall ill more frequently than others living in the same locality ?
Answer. Due to poor immune system, some children fall ill frequently. Balanced diet and proper nutrition for healthy body is required to have a strong immune system.
Question.5 Why are antibiotics not effective for viral disease ?
Answer. Antibiotics generally block the biosynthetic pathways and -they block these pathways of the microbes/bacteria. However, viruses have very few biochemical mechanisms of their own and hence are unaffected by antibiotics.
Question.6 Why does intake of penicillin not affect human cells ? [SAll – 2014]
Answer. It is because penicillin blocks cell wall and formation of biochemical pathways in bacteria. Human cells do not have cell wall, so remain unaffected.
Question.7 You have suffered from chickenpox, when you were in class three. Why will you not suffer from it again ? [SAII -2014]
Answer. It is because our immune system develops antibodies against it when the disease happens for the first time.
Question.8 AIDS is a fatal disease. Explain why. [SAII – 2014]
Answer. In AIDS, immune system of the body is highly weakened and body suffers from severe infections repeatedly which lead to death of the individual. Hence, it is a fatal disease.
Question.9 Common cold spreads faster and is difficult to control. Give reason. [SAII -2014]
Answer. Common cold is a communicable disease. It is an airborne disease i.e., the microbes spread through the air. Thus, common cold spreads faster and is difficult to control.
Question.10. Penicillin is not effective against common cold. Why ?
Answer. Penicillin is an antibiotic which blocks cell wall and formation of biochemical pathways. Common cold is caused by virus which does not have any cell wall or biochemical pathways. Hence, penicillin is not effective against it.
Question.11 Why making anti-viral medicines is harder than making anti-bacterial medicines ?
Answer. Antibiotics block the bacterial processes that build the cell wall. As a result, the growing bacteria become unable to make cell walls and die easily. However, viruses have few biochemical mechanism of their own and these instead use products of the host body. Hence, these remain unaffected by antibiotics.
Question.12 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.
(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— both physical and social. So public cleanliness and good social environment are necessary. Social equality and harmony
are also required. So community health is essential for good individual health.
(c) Cholera is a water-borne disease i.e., it spreads through contaminated water. In the absence of safe supplies of drinking water, villagers suffer with cholera more than the urban people.
Important Topics/Areas/Questions which are
frequently asked in the examination
Question.1 What are the different means by which infectious diseases are spread ?
Answer. The different means by which infectious diseases spread are :
- By direct contact between a healthy and an infected person.
- By indirect contact between a healthy and an infected person.
- Through air.
- Through food.
- By vectors such as mosquitoes and insects etc.
- By the bite of a rabid animal.
Question.2 State giving reasons whether the following statements are correct or not:
- Our surrounding area should be free from stagnant water.
- Staying clean is not necessary as long as you eat a balanced diet.
- Social equality and harmony are necessary for good health.
- Correct, because stagnant water is the breeding place of mosquitoes which causes diseases like malaria, dengue etc.
- Incorrect. Balance diet is essential for a good health but staying clean is also important to remain disease free.
- Correct, because health means a state of physical, mental and social well-being. Our social environment, therefore, plays an important role in our individual health.