CBSE Class 9 Biology Why Do We Fall Ill MCQs Set 08

Answer: (a) Arthritis

Explanation:
1. Arthritis is a disease of the joints and does not spread from person to person.
2. The others are caused by pathogens.

Teacher's Note:
1. Non-infectious diseases include cancer and diabetes.
2. They are not caused by germs.

Answer: (d) Incubation period

Explanation:
1. The time between the entry of the pathogen and the first symptoms is the incubation period.
2. It varies from disease to disease.

Teacher's Note:
1. The pathogen multiplies during this time.
2. A person can spread some diseases during it.

Answer: (c) Disease and mental tension

Explanation:
1. Health means physical, mental and social well-being, so a healthy person has no disease and no mental tension.
2. Not all bacteria are harmful.

Teacher's Note:
1. Being free from only disease is not enough.
2. Social well-being is also part of health.

Answer: (b) Cancer

Explanation:
1. Cancer is caused by uncontrolled division of cells and does not spread from person to person.
2. Typhoid, measles and syphilis are infectious.

Teacher's Note:
1. Cancer can result from genes or the environment.
2. It is a non-communicable disease.

Answer: (b) Anopheles mosquito

Explanation:
1. The female Anopheles mosquito carries Plasmodium.
2. It passes it on through its bite.

Teacher's Note:
1. Aedes spreads dengue.
2. Malaria is a protozoan disease.

Answer: (a) Viruses, bacteria and fungi

Explanation:
1. Pathogens include viruses, bacteria, fungi, protozoa and worms.
2. Measles, mumps and chicken pox are diseases, not agents.

Teacher's Note:
1. Cholesterol is not a pathogen.
2. Protozoa and worms are also pathogens.

Answer: (b) AIDS

Explanation:
1. The HIV virus that causes AIDS spreads through infected blood and needles.
2. It also spreads by sexual contact and from mother to child.

Teacher's Note:
1. Only tested blood should be used.
2. Needles should be sterilised.

Answer: (b) Congenital disease

Explanation:
1. Haemophilia is an inherited disease present from birth, in which blood does not clot properly.
2. So it is congenital.

Teacher's Note:
1. It is caused by a gene on the X chromosome.
2. It is not caused by pathogens.

Answer: (c) Respiratory system

Explanation:
1. Polluted air contains dust and harmful gases that affect the lungs and airways.
2. So the respiratory system is affected.

Teacher's Note:
1. Asthma and bronchitis are examples.
2. Clean air is essential for health.

Answer: (a) Cholera

Explanation:
1. Houseflies carry germs from dirt and faeces to food and spread cholera, typhoid and dysentery.
2. Mosquitoes carry malaria, dengue and yellow fever.

Teacher's Note:
1. Cover food to keep flies away.
2. A vector carries a pathogen from one host to another.

Answer: (a) Cholera

Explanation:
1. Cholera is caused by Vibrio cholerae, which spreads through contaminated food and water.
2. TB is airborne, and syphilis and AIDS spread by contact.

Teacher's Note:
1. Boiling water kills the germs.
2. Handwashing prevents spread.

Answer: (b) Leprosy

Explanation:
1. Leprosy is caused by the bacterium Mycobacterium leprae.
2. Rabies and AIDS are viral, and cancer is not infectious.

Teacher's Note:
1. Bacteria also cause TB, cholera and typhoid.
2. Antibiotics treat bacterial diseases.

Answer: (b) Mycobacterium

Explanation:
1. Mycobacterium tuberculosis causes TB.
2. Salmonella causes typhoid.

Teacher's Note:
1. TB mainly affects the lungs.
2. It is treated with a long course of antibiotics.

Answer: (c) Salmonella typhi

Explanation:
1. Salmonella typhi is the bacterium that causes typhoid.
2. It spreads through contaminated food and water.

Teacher's Note:
1. Typhoid causes prolonged fever.
2. The Widal test detects it.

Answer: (d) Virus

Explanation:
1. The common cold is caused by viruses, mainly rhinoviruses.
2. Antibiotics do not cure it.

Teacher's Note:
1. It spreads through droplets.
2. It usually goes away on its own.

Answer: (d) Common cold, AIDS

Explanation:
1. The common cold and AIDS are both caused by viruses.
2. Typhoid and TB are bacterial, malaria is protozoal and ringworm is fungal.

Teacher's Note:
1. Learn the pathogen type of each disease.
2. Viral diseases are prevented by vaccines.

Answer: (c) Fungi

Explanation:
1. Ringworm and athlete's foot are fungal skin infections.
2. They spread in moist, unclean conditions.

Teacher's Note:
1. Keep the skin dry and clean.
2. Antifungal creams treat them.

Answer: (d) Resistance

Explanation:
1. Resistance is the body's ability to fight off an infection.
2. Pathogenicity and virulence describe the pathogen's ability to cause disease.

Teacher's Note:
1. Good nutrition helps resistance.
2. Vaccination also increases it.

Answer: (b) Common cold

Explanation:
1. There is no vaccine for the common cold because many different viruses cause it.
2. Polio, tetanus and TB have vaccines (BCG for TB).

Teacher's Note:
1. Cold viruses change rapidly.
2. Immunisation is available for many serious diseases.

Answer: (a) Develops resistance against the attack of a disease

Explanation:
1. A vaccine prepares the immune system so that it can fight a disease.
2. It does not work against every disease.

Teacher's Note:
1. The immune system makes memory cells.
2. It does not kill germs in the environment.

Answer: (c) Immunology

Explanation:
1. Immunology is the study of the immune system and resistance to disease.
2. Pathology is the study of diseases.

Teacher's Note:
1. Cytology is the study of cells.
2. Edward Jenner is called the father of immunology.

Answer: (b) Polio

Explanation:
1. The oral polio vaccine is given as drops in the mouth.
2. Tetanus vaccine is injected.

Teacher's Note:
1. The Pulse Polio programme uses it.
2. India was declared polio-free in 2014.

Answer: (c) Edward Jenner

Explanation:
1. Edward Jenner discovered the smallpox vaccine in 1796 using cowpox.
2. Louis Pasteur developed vaccines for rabies and anthrax later.

Teacher's Note:
1. Smallpox has been wiped out.
2. The word vaccine comes from vacca, meaning cow.