CBSE Class 9 Science Why do we fall ill Sure Shot Questions Set 03

CBSE Class 9 Science Why do we fall ill Sure Shot Questions C. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

ASSIGNMENT QUESTIONS SET - 3
CHAPTER - 13
WHY DO WE FALL ILL

1. Which one of the following is not a viral disease? [1 Mark]
(a) Dengue
(b) AIDS
(c) Typhoid
(d) Influenza

Answer: (c) Typhoid

1. Typhoid is caused by the bacterium Salmonella typhi.
2. Dengue, AIDS, and Influenza are caused by viruses.
3. Hence, the correct option is (c).

Teacher's Note:
a) Identify the causative pathogen for each disease listed.
b) Bacterial infections respond to antibiotics, whereas viral infections do not.

2. Which one of the following is not a bacterial disease? [1 Mark]
(a) Cholera
(b) Tuberculosis
(c) Anthrax
(d) Influenza

Answer: (d) Influenza

1. Influenza is caused by the influenza virus.
2. Cholera, tuberculosis, and anthrax are caused by bacteria.
3. Hence, the correct option is (d).

Teacher's Note:
a) Distinguish clearly between bacterial and viral pathogens.
b) Influenza spreads rapidly via airborne droplets during coughing or sneezing.

3. Which one of the following disease is not transmitted by mosquito? [1 Mark]
(a) Brain fever
(b) Malaria
(c) Typhoid
(d) Dengue

Answer: (c) Typhoid

1. Typhoid is transmitted through contaminated food and water.
2. Malaria, dengue, and brain fever are vector-borne diseases transmitted by mosquitoes.
3. Hence, the correct option is (c).

Teacher's Note:
a) Vectors are organisms that transmit infectious diseases from one host to another.
b) Focus on modes of transmission when classifying communicable diseases.

4. Which one of the following disease is caused by bacteria? [1 Mark]
(a) Typhoid
(b) Anthrax
(c) Tuberculosis
(d) Malaria

Answer: (c) Tuberculosis
(Note: Typhoid and anthrax are also bacterial diseases, but tuberculosis is the classic representative option frequently highlighted in this context; the official key points to tuberculosis or any valid bacterial option.)

1. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
2. Malaria is caused by a protozoan.
3. Hence, the correct option is (c).

Teacher's Note:
a) Multiple correct options may appear in poorly framed test banks.
b) Always verify specific textbook classifications for board exams.

5. Which one of the following diseases is caused by protozoans? [1 Mark]
(a) Malaria
(b) Influenza
(c) AIDS
(d) Cholera

Answer: (a) Malaria

1. Malaria is caused by protozoan parasites of the genus Plasmodium.
2. Influenza and AIDS are viral, while cholera is bacterial.
3. Hence, the correct option is (a).

Teacher's Note:
a) Protozoans are single-celled eukaryotic organisms.
b) Remember that Plasmodium requires two hosts to complete its life cycle.

6. Which one of the following has a long term effect on the health of an individual? [1 Mark]
(a) Common cold
(b) Chicken pox
(c) Chewing tobacco
(d) Stress

Answer: (c) Chewing tobacco

1. Chewing tobacco leads to chronic conditions such as oral cancer and cardiovascular disease.
2. Common cold and chicken pox are acute diseases with short-term effects.
3. Hence, the correct option is (c).

Teacher's Note:
a) Acute diseases last for a very short period of time.
b) Chronic diseases last for a long time, even as much as a lifetime, causing drastic long-term damage.

7. Which of the following can make you ill if you come in contact with an infected person? [1 Mark]
(a) High blood pressure
(b) Genetic abnormalities
(c) Sneezing
(d) Blood cancer

Answer: (c) Sneezing

1. Sneezing releases infectious droplet nuclei into the air, spreading communicable diseases.
2. High blood pressure, genetic abnormalities, and blood cancer are non-infectious diseases.
3. Hence, the correct option is (c).

Teacher's Note:
a) Infectious diseases spread from an infected person to a healthy person through air, water, or vectors.
b) Non-infectious diseases remain confined to the individual and are caused by internal or lifestyle factors.

8. AIDS cannot be transmitted by [1 Mark]
(A) sexual contact
(B) hugs
(C) breast feeding
(D) blood transfusion

Answer: (B) hugs

1. HIV/AIDS is transmitted through sexual contact, infected blood transfusion, and from mother to child via breast feeding.
2. Casual physical contact such as hugging, shaking hands, or sharing food does not transmit the virus.
3. Hence, the correct option is (B).

Teacher's Note:
a) Focuses on modes of transmission of communicable diseases.
b) Remember that HIV is not spread by casual contact.

9. Making anti-viral drugs is more difficult than making anti-bacterial medicines because [1 Mark]
(A) viruses make use of host machinery
(B) viruses are on the border line of living and non-living
(C) viruses have very few biochemical mechanisms of their own
(D) viruses have a protein coat

Answer: (C) viruses have very few biochemical mechanisms of their own

1. Viruses use the host cell's machinery to multiply and have very few biochemical pathways of their own.
2. Due to this, there are very few virus-specific targets available for drugs to attack without harming the host cells.
3. Hence, the correct option is (C).

Teacher's Note:
a) Understands the basic biological difference between viruses and bacteria.
b) A common trap is choosing option (A), which is a consequence rather than the primary reason for drug difficulty.

10. Which one of the following causes kala-azar? [1 Mark]
(A) Ascaris
(B) Trypanosoma
(C) Leishmania
(D) Bacteria

Answer: (C) Leishmania

1. Kala-azar is caused by protozoan parasites belonging to the genus Leishmania.
2. Ascaris causes ascariasis, and Trypanosoma causes sleeping sickness.
3. Hence, the correct option is (C).

Teacher's Note:
a) Direct factual recall of disease-causing pathogens.
b) Do not confuse protozoan parasites with bacterial infections.

11. If you live in a overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases [1 Mark]
(A) Cancer
(B) AIDS
(C) Air borne diseases
(D) Cholera

Answer: (C) Air borne diseases

Overcrowded and poorly ventilated living conditions facilitate the easy spread of microbes through the air from an infected person. 1. Airborne diseases like tuberculosis, pneumonia, and the common cold spread rapidly in such environments.
2. Cancer and AIDS are not caused directly by environmental overcrowding.
3. Hence, the correct option is (C).

Teacher's Note:
a) Relates housing conditions to the spread of infectious diseases.
b) Emphasizes the importance of ventilation in preventing airborne infections.

12. Which disease is not transmitted by mosquitoes? [1 Mark]
(A) Dengue
(B) Malaria
(C) Brain fever or encephalitis
(D) Pneumonia

Answer: (D) Pneumonia

1. Dengue is transmitted by Aedes mosquitoes, malaria by Anopheles mosquitoes, and some forms of encephalitis by mosquitoes.
2. Pneumonia is an airborne bacterial or viral infection, not a vector-borne disease.
3. Hence, the correct option is (D).

Teacher's Note:
a) Distinguishes between vector-borne and airborne diseases.
b) Pneumonia affects the lungs and spreads through droplets.

13. Which one of the following is not important for individual health? [1 Mark]
(A) Living in clean space
(B) Good economic condition
(C) Social equality and harmony
(D) Living in a large and well furnished house

Answer: (D) Living in a large and well furnished house

1. Individual health depends on physical surroundings, economic stability, and social harmony.
2. The size and furnishing of a house do not determine good health, whereas cleanliness, financial stability, and peace do.
3. Hence, the correct option is (D).

Teacher's Note:
a) Explores the broad definition of health beyond mere physical absence of disease.
b) Distinguish between essential needs and luxurious living conditions.

14. Choose the wrong statement [1 Mark]
(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: (C) Peptic ulcers are caused by eating acidic food

1. Peptic ulcers are caused by the bacterium Helicobacter pylori, not by eating acidic food.
2. High blood pressure, genetic causes of cancer, and bacterial causes of acne are correctly stated in the other options.
3. Hence, the correct option is (C).

Teacher's Note:
a) Highlights the discovery of bacterial causes for stomach ulcers.
b) A common misconception is that spicy or acidic foods directly cause ulcers.

15. We should not allow mosquitoes to breed in our surroundings because they [1 Mark]
(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) are vectors for many diseases

1. Mosquitoes act as vectors that transmit dangerous pathogens causing malaria, dengue, and chikungunya.
2. Controlling their breeding helps prevent the spread of these infectious vector-borne diseases.
3. Hence, the correct option is (B).

Teacher's Note:
a) Defines the role of vectors in disease transmission.
b) Focuses on preventive health measures in community surroundings.

16. You are aware of Polio Eradication Programme in your city. Children are vaccinated because [1 Mark]
(A) vaccination kills the polio causing microorganisms
(B) prevents the entry of polio causing organism
(C) it creates immunity in the body
(D) all the above

Answer: (C) it creates immunity in the body

1. Vaccines introduce weakened or dead pathogens into the body.
2. This stimulates the immune system to produce antibodies without causing the disease.
3. These antibodies provide long term immunity against future infections.
4. Hence, the correct option is (C).

Teacher's Note:
a) Vaccines work by priming the immune system to recognize specific disease agents.
b) They do not directly kill existing microorganisms inside the body.

17. Viruses, which cause hepatitis, are transmitted through [1 Mark]
(A) air
(B) water
(C) food
(D) personal contact

Answer: (B) water

1. Hepatitis A virus is primarily transmitted through the ingestion of contaminated water or food.
2. Waterborne transmission is common in areas with poor sanitation.
3. Hence, the correct option is (B).

Teacher's Note:
a) Hepatitis viruses like Hepatitis A and E spread mainly via the faecal-oral route through contaminated water.
b) Note that Hepatitis B and C spread through blood and body fluids.

18. Vectors can be defined as [1 Mark]
(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) animals carry the infecting agents from sick person to another healthy person

1. Vectors are intermediate organisms that transmit pathogens from an infected host to a healthy individual.
2. Common examples include mosquitoes, ticks, and houseflies.
3. Hence, the correct option is (A).

Teacher's Note:
a) Vectors play a crucial role in spreading vector-borne diseases like malaria and dengue.
b) They differ from pathogens, which are the actual disease-causing microorganisms.

19. Give two examples for each of the following [2 Marks]
(a) Acute diseases
(b) Chronic diseases
(c) Infectious diseases
(d) Non-infectious diseases

Answer:
1. Acute diseases: Common cold and cholera.
2. Chronic diseases: Tuberculosis and diabetes.
3. Infectious diseases: Malaria and viral fever.
4. Non-infectious diseases: Cancer and hypertension.

Teacher's Note:
a) Acute diseases last for a very short period of time.
b) Chronic diseases last for a long time, even as much as a lifetime, causing long term drastic effects on health.

20. Name two diseases caused by Protozoans. What are their causal organisms? [2 Marks]

Answer:
1. Malaria is caused by the protozoan Plasmodium.
2. Kala-azar is caused by the protozoan Leishmania.

Teacher's Note:
a) Protozoans are single-celled eukaryotic microorganisms.
b) Always learn the scientific genus names alongside the common names of protozoan diseases.

21. Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time? [2 Marks]

Answer:
1. Peptic ulcers are caused by the bacterium Helicobacter pylori.
2. It was discovered for the first time by two Australian physicians, Robin Warren and Barry Marshall, in 1979.

Teacher's Note:
a) Barry Marshall and Robin Warren were awarded the Nobel Prize for this groundbreaking discovery.
b) Previously, lifestyle and stress were incorrectly thought to be the sole causes of peptic ulcers.

22. What is an antibiotic? Give two examples [2 Marks]

Answer:
1. Antibiotics are chemical substances produced by microorganisms that can kill or inhibit the growth of other disease-causing bacteria.
2. Two common examples of antibiotics are penicillin and erythromycin.

Teacher's Note:
a) Antibiotics target bacterial biochemical pathways, which is why they are ineffective against viral infections like the common cold.
b) Alexander Fleming discovered the first antibiotic, penicillin, from the fungus Penicillium notatum.

23. Fill in the blanks [2 Marks]
(a) Pneumonia is an example of - - - disease.
(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 from one person to another are called - - - .

Answer:
(a) Pneumonia is an example of infectious (or bacterial/communicable) disease.
(b) Many skin diseases are caused by fungi.
(c) Antibiotics commonly block biochemical pathways important for the growth of bacteria.
(d) Living organisms carrying the infecting agents from one person to another are called vectors.

Teacher's Note:
a) Read each sentence carefully to identify the biological category being tested.
b) Ensure correct spelling of scientific terms like fungi and bacteria.

24. Name the target organs for the following diseases [2 Marks]
(a) Hepatitis targets - - - .
(b) Fits or unconsciousness targets - - - .
(c) Pneumonia targets - - - .
(d) Fungal disease targets - - - .

Answer:
(a) Hepatitis targets the liver.
(b) Fits or unconsciousness targets the brain.
(c) Pneumonia targets the lungs.
(d) Fungal disease targets the skin.

Teacher's Note:
a) Pathogens often choose specific target organs based on their entry point and tissue tropism.
b) Symptoms of a disease largely depend upon the targeted organ system.

25. Who discovered ‘vaccine’ for the first time? Name two diseases which can be prevented by using vaccines. [2 Marks]

Answer:
1. Edward Jenner discovered the vaccine for the first time (specifically for smallpox in 1796).
2. Two diseases that can be prevented by using vaccines are Polio and Measles.

Teacher's Note:
a) Edward Jenner used cowpox pus to provide immunity against smallpox.
b) Vaccination forms the cornerstone of preventive healthcare and public health eradication programs.

26. Fill in the blanks [5 Marks]
(a) - - - disease continues for many days and causes - - - on body.
(b) - - - disease continues 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 - - - disease.
(e) Many skin diseases are caused by - - - .

Answer:
1. (a) Chronic, lasting damage / long term effect.
2. (b) Acute.
3. (c) Health.
4. (d) Acute (or infectious).
5. (e) Fungi.

Teacher's Note:
a) Distinguishes between chronic and acute disorders based on duration.
b) Basic definitions of health as laid down by the World Health Organization.
c) Common cold is a typical short-duration viral infection.
d) Fungal infections commonly affect outer skin layers in warm conditions.

27. Classify the following diseases as infectious or non-infectious. [3 Marks]
(a) AIDS
(b) Tuberculosis
(c) Cholera
(d) High blood pressure
(e) Heart disease
(f) Pneumonia
(g) Cancer

Answer:
1. Infectious diseases: AIDS, Tuberculosis, Cholera, Pneumonia.
2. Non-infectious diseases: High blood pressure, Heart disease, Cancer.
3. Infectious diseases are caused by micro-organisms, while non-infectious are caused by internal or genetic factors.

Teacher's Note:
a) Categorization relies on whether a pathogen can spread from person to person.
b) Non-infectious ailments often stem from lifestyle, genetics, or metabolic failures.
c) Ensure students list all sub-parts explicitly with correct headings.

28. Name any two groups of micro-organisms from which antibiotics could be extracted. [2 Marks]

Answer:
1. Bacteria.
2. Fungi.

Teacher's Note:
a) Antibiotics are chemical substances produced by micro-organisms that kill or inhibit the growth of other microbes.
b) Penicillin, for instance, is extracted from the fungus Penicillium.

29. Name any three diseases transmitted through vectors. [3 Marks]

Answer:
1. Malaria.
2. Dengue.
3. Filariasis (or Chikungunya / Yellow fever).

Teacher's Note:
a) Vectors are intermediate organisms that transfer pathogens from an infected host to a healthy person.
b) Mosquitoes act as common vectors for several protozoan and viral infections.
c) Controlling vector breeding is vital for disease prevention.

30. Explain giving reasons [4 Marks]
(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:
1. (a) A balanced diet provides all essential nutrients, vitamins, and minerals required for proper growth and strong immune function.
2. (b) External surroundings dictate exposure to pathogens, pollutants, and sanitary standards directly influencing physical well-being.
3. (c) Stagnant water serves as a breeding ground for mosquitoes which transmit deadly vector-borne diseases.
4. (d) Economic stability ensures access to proper nutrition and medical care, while social harmony reduces stress and promotes mental peace.

Teacher's Note:
a) Health is multidimensional, encompassing physical, mental, and social aspects.
b) Environmental hygiene directly prevents infectious disease outbreaks.
c) Economic status dictates the baseline standard of living and hygiene.
d) Clear reasoning must link each condition directly to physiological or psychological outcomes.

31. What is a disease? How many types of diseases have you studied? Give examples. [3 Marks]

Answer:
1. A disease is a condition of abnormal functioning of the body or mind characterized by specific signs and symptoms.
2. Two main types are studied: Acute diseases (short duration, e.g., common cold) and Chronic diseases (long duration, e.g., diabetes, tuberculosis).
3. They can also be broadly divided into infectious (communicable) and non-infectious (non-communicable) categories.

Teacher's Note:
a) Accurate definition must mention impairment of normal bodily functions.
b) Give clear examples for both acute and chronic classifications.
c) Emphasize how chronic diseases have long-term drastic effects on overall health.

32. What do you mean by disease symptoms? Explain giving two examples? [3 Marks]

Answer:
1. Disease symptoms are the physical manifestations or feelings that indicate the presence of a disease in the body.
2. Example 1: Headache indicates pain and potential stress, migraine, or infection.
3. Example 2: Coughing indicates irritation or infection in the respiratory tract.

Teacher's Note:
a) Symptoms are subjective indications experienced by the patient, unlike objective signs observed by doctors.
b) They help physicians identify the affected organ system.
c) Multiple diseases can share similar generalized symptoms like fever or fatigue.

33. Why is immune system essential for our health? [2 Marks]

Answer:
1. The immune system recognizes, fights off, and destroys foreign pathogens like bacteria, viruses, and fungi that enter the body.
2. It provides specialized cells and antibodies to prevent infections from developing into full-blown diseases.

Teacher's Note:
a) Immunity forms the primary internal defense mechanism against microbial invasion.
b) A compromised immune system makes individuals prone to frequent and severe infections.

34. What precautions will you take to justify “prevention is better than cure”. [3 Marks]

Answer:
1. Maintain personal and environmental hygiene by keeping surroundings clean and consuming safe drinking water.
2. Eat a balanced diet rich in essential nutrients to keep the immune system strong.
3. Get vaccinated timely against common infectious diseases to develop active immunity.

Teacher's Note:
a) Prevention avoids the physical, mental, and financial costs associated with treating an established disease.
b) Sanitation and vaccination are core public health pillars of preventive medicine.
c) Mentioning nutrition highlights the lifestyle aspect of disease avoidance.

35. Why do some children fall ill more frequently than others living in the same locality? [3 Marks]

Answer:
1. Differences in nutritional status; children with poor diets have weaker immune systems.
2. Varying access to clean drinking water and hygienic living conditions.
3. Genetic differences or lack of proper immunization can make some children more susceptible to infections.

Teacher's Note:
a) Environmental exposure alone does not determine illness; internal resistance matters equally.
b) Malnutrition is a major factor predisposing children to recurrent infections.
c) Timely vaccination history creates disparities in health outcomes among peers.

36. Why are antibiotics not effective for viral disease? [2 Marks]

Answer:
1. Viruses do not possess their own metabolic machinery or cell walls like bacteria do.
2. Antibiotics function by blocking biochemical pathways peculiar to bacteria, which viruses lack and bypass entirely.

Teacher's Note:
a) Misuse of antibiotics for viral colds or flu contributes to global antibiotic resistance.
b) Antiviral medications operate via different mechanisms than antibacterial drugs.

37. Becoming exposed to or infected with an infectious microbe does not necessarily mean developing noticeable disease. Explain. [3 Marks]

Answer:
1. The severity of disease manifestation depends heavily on the strength and efficiency of the individual's immune system.
2. If the immune system is robust, it neutralizes the pathogen before symptoms can manifest.
3. The number of microbes entering the body may also be too small to cause significant disruption.

Teacher's Note:
a) Exposure introduces the pathogen, but host immunity determines the outcome.
b) Sub-clinical infections occur frequently without noticeable sickness.
c) General health and nutrition directly govern immune responsiveness.

38. Give any four factors necessary for a healthy person. [4 Marks]

Answer:
1. Physical well-being and proper functioning of body organs.
2. Access to a balanced diet and clean drinking water.
3. A hygienic and pollution-free physical environment.
4. Mental and social harmony free from psychological stress.

Teacher's Note:
a) Health is defined as a state of complete physical, mental, and social well-being.
b) Covers both internal biological factors and external environmental conditions.
c) Emphasizes that absence of disease alone does not constitute true health.
d) Economic and social security underpins overall community wellness.

39. Why is AIDS considered to be a ‘Syndrome’ and not a disease? [2 Marks]

Answer:
1. AIDS stands for Acquired Immuno Deficiency Syndrome, where the virus attacks the immune system.
2. It is called a syndrome because it does not present a single distinct disease, but rather a collection of symptoms and infections due to a failed immune system.

Teacher's Note:
a) A syndrome represents a group of concurrent signs and symptoms pointing to a common underlying defect.
b) HIV destroys helper T-cells, leaving the body vulnerable to multiple opportunistic infections.