NCERT Class-9 Science Solutions: Chapter 13-Why Do We Fall Ill Part 3

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Question 17:

Viruses, which cause hepatitis, are transmitted through

1. Air

2. Water

3. Food

4. Personal contact

Answer: B

Question 18:

Vectors can be defined as

1. Animals carry the infecting agents from sick person to another healthy person

2. Microorganisms which cause many diseases

3. Infected person

4. Diseased plants

Answer: A

Short Answer Questions

Question 19:

Give two examples for each of the following

1. Acute diseases

2. Chronic diseases

3. Infectious diseases

4. Non-infectious diseases

Answer:

(A) Acute diseases:

Viral fever, Flu

(B) Chronic diseases:

Elephantiasis, Tuberculosis (TB)

(C) Infectious diseases:

Small pox, Chicken pox

(D) Non-infectious diseases:

Diabetes, Goiter

Question 20:

1. Name two diseases caused by Protozoans

2. What are their causal organisms?

Answer:

Sleeping sickness caused by Trypanosoma / Malaria by plasmodium

Kala-azar caused by Leishmania

Question 21:

1. Which bacterium causes peptic ulcers?

2. Who discovered the above pathogen for the first time?

Answer:

Helicobacter pylori bacterium causes peptic ulcers.

Marshall and Warren discovered the pathogen for the first time

Question 22:

What is an antibiotic? Give two examples

Answer:

Antibiotic is a chemical substance that kill bacteria, secreted by microorganisms which can kill the pathogens.

Examples, Penicillin and Streptomycin

Question 23:

Fill in the blanks

1. Pneumonia is an example of ——— disease.

2. Many skin diseases are caused by———.

3. Antibiotics commonly block biochemical pathways important for the growth of ———.

4. Living organisms carrying the infecting agents from one person to another are called ———.

Answer:

Pneumonia is an example of communicable disease.

Many skin diseases are caused by fungi

1. Antibiotics commonly block biochemical pathways important for the growth of bacteria.

2. Living organisms carrying the infecting agents from one person to another are called vector.