Diseases: Cause and Control
Solutions for Biology, Class 9, ICSE
Assertion Reason Type
5 questionsAssertion (A): When the disease is widely distributed worldwide, it is termed as a sporadic disease.
Reason (R): Sporadic diseases are not localised, their individual cases are scattered; for example malaria, cholera, etc.
- A is True and R is False.
- A is False and R is True.
- Both A and R are True.
- Both A and R are False.
Answer:
Both A and R are False.
Reason — A disease widely distributed worldwide is called a pandemic (e.g. COVID-19). Sporadic disease refers to diseases that occur infrequently and irregularly, usually in isolated or scattered cases.
While sporadic diseases occur in scattered cases, malaria and cholera are not good examples — they often occur in epidemics or are endemic in certain areas.
Assertion (A): Goitre is a kind of a nutritional deficiency disease as well as metabolic disease.
Reason (R): Goitre is caused due to the deficiency of iron which is also required for the synthesis of thyroxine by thyroid gland.
- A is True and R is False.
- A is False and R is True.
- Both A and R are True.
- Both A and R are False.
Answer:
A is True and R is False.
Reason — Goitre is an enlargement of the thyroid gland. It is caused by a deficiency of iodine, which is a nutritional deficiency. Since the thyroid controls metabolism through thyroxine production, goitre is also classified as a metabolic disease.
Goitre is caused due to a deficiency of iodine, not iron. Iodine is essential for the synthesis of thyroxine, the thyroid hormone.
Assertion (A): The disease-causing germs are called vectors.
Reason (R): The transmission of germs from one person to another is carried out by certain organisms which are termed as vectors.
- A is True and R is False.
- A is False and R is True.
- Both A and R are True.
- Both A and R are False.
Answer:
A is False and R is True.
Reason — Disease-causing germs are called pathogens (e.g., bacteria, viruses). Vectors are organisms (usually insects) that transmit pathogens from one host to another.
Vectors like mosquitoes, houseflies, and ticks help in spreading pathogens. Example: Anopheles mosquito transmits Plasmodium (causes malaria).
Assertion (A): Taeniasis is the disease caused by tapeworms. It spreads by eating infected pork or beef.
Reason (R): Pigs or cows accidentally ingest the eggs of tapeworm which later on form larval stages. These larvae settle in the muscles of pigs or cows.
- A is True and R is False.
- A is False and R is True.
- Both A and R are True.
- Both A and R are False.
Answer:
Both A and R are True.
Reason — Taeniasis is caused by: Taenia solium (from infected pork) or Taenia saginata (from infected beef). Humans get the disease by eating undercooked or raw meat containing larval cysts of the tapeworm.
The tapeworm eggs, passed in human feces, can contaminate food or water sources. Pigs or cows ingest these eggs, which develop into larvae (cysticerci) in their muscles.
Assertion (A): The viruses are extremely small substances made of nucleic acids (DNA) and histones.
Reason (R): Viruses are considered as a connecting link between the living and non-living beings as they can multiply and be crystallized and stored for years.
- A is True and R is False.
- A is False and R is True.
- Both A and R are True.
- Both A and R are False.
Answer:
A is False and R is True.
Reason — Viruses are extremely small and are made of: A nucleic acid core (either DNA or RNA, never both), and a protein coat called a capsid. However, viruses do not contain histones.
Viruses behave like living organisms when inside a host cell (they replicate), and like non-living things outside a host (they can be crystallized and stored without metabolism or reproduction).
Long Answer Type
6 questionsAnswer:
(a) BCG — BCG (Bacillus Calmette Guerin) is a vaccine which is effective against the bacterial disease tuberculosis(TB). It develops immunity to tuberculosis.
(b) Incubation period — Incubation period is the period between the entry of germs and appearance of the first symptoms of the disease. All infectious diseases have a certain incubation period.
(c) Chicken pox — The disease is a contagious disease occurring mainly in children, and is caused by Herpes Varicella zoster virus. The disease rapidly spreads through close contact with the person infected.
(d) Hepatitis A — It is caused by the Hepatitis A virus and is a viral disease that results in liver inflammation. It is transferred primarily through contaminated water and food.
Answer:
The causes, symptoms and preventive measures of these diseases are as given below:
- Malaria
- Causes — Protozoan, Plasmodium.
- Symptoms — Chills, high fever, profuse sweating, severe headache, nausea, vomiting, fatigue and body pain.
- Preventive measures — Avoid mosquito bites using mosquito repellents and nets avoid being around stagnant water.
- Chicken Pox
- Causes — Virus, Varicella zoster.
- Symptoms — Rashes near the back and the chest eventually spreading to arms, face, legs and head.
- Preventive measures — Active immunisation by administering live attenuated vaccine containing Varicella.
- Tuberculosis
- Causes — Mycobacterium tuberculosis.
- Symptoms — Persistent cough, afternoon fever, bloody mucus, loss of weight, fatigue and chest pain.
- Preventive measures — BCG vaccination and isolation of the patient.
Answer:
The different ways in which infectious diseases can spread are as follows:
- Direct contact — Person to person, animal to person and expected mother to child.
- Indirect contact — Doorknob, phone, etc.
- Droplet transmission — Sneezing, Coughing, etc.
- Particle transmission — Air particles can transfer infectious diseases
- Bites and Stings — Mosquitoes, lice, ticks, etc.
- Food Contamination — Food, beverages, etc.
Answer:
(a) Difference between pandemic and sporadic diseases :
| Pandemic diseases | Sporadic diseases |
|---|---|
| A pandemic disease is an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population. | Sporadic diseases are characterized by the occurrence of isolated individual cases or occasional outbreaks of a disease. |
| Example: AIDS, COVID-19 | Example: Malaria, Cholera |
(b) Difference between communicable and non-communicable diseases :
| Communicable diseases | Non-communicable diseases |
|---|---|
| They are transmitted from infected person to healthy person. | They are non-transmissible. |
| They are caused by germs. | They are not caused by germs. |
| Example: Cholera, Malaria. | Example: Diabetes, beri-beri. |
(c) Difference between allergens and carcinogens :
| Allergens | Carcinogens |
|---|---|
| Any agent that causes allergy is called an allergen. | Any agent that causes cancer is called a carcinogen. |
| Allergens cause the immune system to overreact producing an allergic response. | Carcinogens cause cancer by damaging DNA or interfering with cellular processes, leading to uncontrolled cell growth and the formation of tumors. |
| Example: Dust, Smoke, Pollen | Example: Tobacco, Radiations, Pollutants |
(d) Difference between endemic and epidemic diseases :
| Endemic diseases | Epidemic diseases |
|---|---|
| An endemic disease is found in a certain area only attacking a fewer number of people. | An epidemic disease breaks out and spreads from place to place affecting large number of people at the same time. |
| Example: Yellow fever in African countries, Goitre in Sub-Himalayan region. | Example: Plague in India in 1994, H1N1 influenza pandemic in 2009. |
(e) Difference between pathogen and vector :
| Pathogen | Vector |
|---|---|
| A pathogen is a microorganism or agent that can cause disease in a host organism. | A vector is an organism or agent that can transmit a pathogen from one host to another. |
| Pathogen are generally bacteria, virus, protozoa etc. | Vector are generally mosquitoes, flies, rats, etc. |
| Example: Plasmodium, Mycobacterium tuberculosis | Example: Aedes mosquito, Tsetse fly, Rats. |
Answer:
Five important preventive measures advised by WHO to minimise the chances of getting COVID-19 are:
- Staying at home.
- Regularly washing hands with soap and water.
- Avoiding crowded spaces.
- Wearing a mask in public and maintaining a safe distance.
- Getting vaccinated.
Multiple Choice Type
11 questionsAnswer:
Anopheles mosquito
Reason — The malarial pathogen Plasmodium, is transferred from an infected person to a healthy person through the bite of female Anopheles mosquito.
Answer:
Acquired Immuno Deficiency Syndrome
Reason — AIDS stands for Acquired Immuno Deficiency Syndrome.
Which of the following statements about HIV is correct?
- HIV primarily attacks red blood cells, leading to anemia.
- HIV weakens the immune system, which can lead to cancer.
- HIV is caused by a bacterium and can be treated with antibiotics.
- HIV infection is detectable immediately after exposure.
Answer:
HIV weakens the immune system, which can lead to cancer.
Reason — HIV (Human Immunodeficiency Virus) attacks the body's immune system, particularly the white blood cells. Over time, this weakens the immune system, making the body vulnerable to opportunistic infections and certain types of cancer.
Progress Check 1
2 questionsShort Answer Type
3 questionsAnswer:
(a) Infection — The transmission of diseases from one person to another is called infection.
(b) Pathogen — A pathogen is a disease-causing micro-organism.
(c) Incubation — Incubation period is the period between the entry of germs and appearance of the first symptoms of the disease. All infectious diseases have a certain incubation period.
(d) Disease — Disease is a departure from normal health through structural or functional disorder of the body.
(e) Vaccine — Vaccine is a biological formulation that consist of dead or weakened disease causing organism that provides active acquired immunity to a particular infectious disease.
Structured Application Skill Type
2 questionsThe diagram given below represents a kind of microorganism. Study the same and answer the following questions:
(a) Identify the microorganism.
(b) To which category of microorganisms does it belong ?
(c) Label the guidelines 1, 2 and 3.
(d) Does it cause any disease? If yes, name the disease.
(e) Mention two ways by which it can be transmitted from one person to another.
Answer:
(a) Human Immunodeficiency Virus (HIV).
(b) Virus
(c) The labelled guidelines are :
- 1 → Viral Protein
- 2 → Protein covering
- 3 → RNA
(d) Yes, it causes the disease called Acquired Immuno Deficiency Syndrome (AIDS).
(e) Two ways by which it can be transmitted from one person to another are:
- Sexual intercourse
- Contaminated blood transfusions
The figure shown below represents an animal. Answer the following questions.
(a) Identify and name the animal.
(b) Write the phylum to which it belongs.
(c) Name the disease caused by this animal.
(d) Write its scientific name.
(e) Mention two common hosts (animals) for this parasite.
Answer:
(a) Tapeworm
(b) Platyhelminthes
(c) Taeniasis
(d) Taenia solium
(e) Cow and Pig
Very Short Answer Type
8 questionsCorrect the following statements by changing the first/last word only.
(a) Sporadic diseases are widely distributed worldwide.
(b) Yellow fever is an epidemic disease.
(c) Chicken pox is caused by a bacterium.
(d) Haemophilia is a kind of an allergy.
(e) Ascariasis is caused by a tapeworm.
Answer:
(a) Pandemic diseases are widely distributed worldwide.
(b) Yellow fever is an endemic disease.
(c) Chicken pox is caused by a virus.
(d) Haemophilia is a kind of genetic disease.
(e) Ascariasis is caused by a roundworm.
Answer:
(a) HIV — Human Immunodeficiency Virus
(b) AIDS — Acquired Immuno Deficiency Syndrome
(c) BCG — Bacillus Calmette-Guerin
(d) COVID-19 — Corona Virus Disease 2019
(e) RNA — Ribo-nucleic Acid
Mention whether the following statements are true (T) or false (F).
(a) Filariasis is transmitted by the housefly.
(b) Malaria is caused by a protozoan.
(c) BCG vaccine is used for chicken pox.
(d) Louis Pasteur discovered a cure for malaria.
(e) AIDS is caused by a bacterium.
(f) HIV is a serious disease, usually fatal.
(g) AIDS is not transmitted by contact with a patient's clothes.
(h) Chicken pox and hepatitis are bacterial diseases.
(i) Goitre is endemic in sub-Himalayan regions of India.
(j) AIDS is caused by a fungus.
(k) Hay fever and asthma are allergies.
(l) Smallpox still occurs in India.
(m) The disease filariasis is caused by the bite of female anopheles mosquito.
Answer:
(a) False
Corrected Statement — Filariasis is transmitted by Culex Mosquito.
(b) True
(c) False
Corrected Statement — BCG vaccine is used for Tuberculosis.
(d) False
Corrected Statement — Louis Pasteur discovered Anthrax vaccine.
(e) False
Corrected Statement — AIDS is caused by a virus named HIV (Human Immunodeficiency Virus).
(f) True
(g) True
(h) False
Corrected Statement — Chicken pox and hepatitis are viral diseases.
(i) True
(j) False
Corrected Statement — AIDS is caused by a virus named HIV (Human Immunodeficiency Virus).
(k) True
(l) False
Corrected Statement — Small pox was eradicated from India in 1979.
(m) False
Corrected Statement — The disease filariasis is caused by the bite of culex mosquito.
Name the following:
(a) The vaccine for preventing tuberculosis ............... .
(b) An organ usually affected by tuberculosis............... .
(c) A disease that weakens body’s defense system against infections ............... .
(d) The microorganism that requires a host to reproduce ............... .
(e) The popular name of the disease filariasis ............... .
Answer:
(a) BCG
(b) Lungs
(c) AIDS
(d) Virus
(e) Elephantiasis
Answer:
(a) Endemic, Epidemic, Pandemic, Sporadic
(b) Communicable and Non-communicable
(c) Arthritis, Cataract
(d) Malaria, Amoebic Dysentery, Sleeping Sickness
(e) Ascariasis, Taeniasis, Filariasis
Answer:
| Column A | Column B |
|---|---|
| Allergy | Hay fever |
| Metabolic disease | Diabetes mellitus |
| Genetic disease | Thalassemia |
| Degenerative disease | Cataract |
| Cancer | Leukemia |
The first pair indicates the kind of relationship that exists between the first two terms. Rewrite and complete the second pair on a similar basis:
(a) April 7 : World health day :: December 1 : ...............
(b) Malaria: Plasmodium :: Filariasis : ...............
(c) Hepatitis: Liver :: Tuberculosis : ...............
(d) Mumps: Viral disease :: Typhoid : ...............
(e) Covid- 19: Pandemic :: Yellow fever : ...............
Answer:
(a) April 7 : World health day :: December 1 : World Aids day.
(b) Malaria: Plasmodium :: Filariasis : Wuchereria bancrofti.
(c) Hepatitis: Liver :: Tuberculosis : Lungs.
(d) Mumps: Viral disease :: Typhoid : Bacterial.
(e) Covid- 19: Pandemic :: Yellow fever : Endemic.
Choose the odd one out and write the category for the remaining terms:
(a) Cholera, Typhoid, Malaria, Tuberculosis
(b) Hepatitis, Ascariasis, Chicken pox, Poliomyelitis
(c) Elephantiasis, Ascariasis, Taeniasis, Hepatitis
(d) Depression, Beri-beri, Scurvy, Night-blindness
(e) Malaria, Amoebiasis, Sleeping sickness, Cataract
Answer:
(a) Odd one out — Malaria
Cholera, Typhoid, Tuberculosis — Bacterial Diseases
(b) Odd one out — Ascariasis
Hepatitis, Chicken pox, Poliomyelitis — Viral diseases
(c) Odd one out — Hepatitis
Elephantiasis, Ascariasis, Taeniasis — Diseases caused by parasitic worms.
(d) Odd one out — Depression
Beri-beri, Scurvy, Night-blindness — Deficiency diseases
(e) Odd one out — Cataract
Malaria, Amoebiasis, Sleeping sickness — Protozoan disease.