Harmful Micro-Organism

Question 1 What are pathogens?

Question 2 What are communicable diseases?

Question 3 Name one disease which spreads by breathing in air contaminated by micro-organism?

Question 4 Name one disease which spreads through insect bite?

Question 5 Name one disease which spreads through infected food or water?

• NCERT Solutions Class 8 Science

Harmful micro-organism

Those micro-organism which cause diseases are called pathogens. They can be bacteria, fungi, virus or protozoa.

Micro-organism cause diseases such as cholera, typhoid, tuberculosis, malaria, smallpox, chickenpox etc. Some micro-organism spoil food, clothing and leather objects.

1) Pathogens enter our body through the air we breathe, the water we drink or the food we eat.

2)The disease causing micro-organism can also get transmitted by direct contact with an infected person or carried through an insect.

Communicable Diseases

Those microbial diseases which can be spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases.

For Example Common cold, cholera, chicken pox, tuberculosis, malaria, AIDS etc.

A person suffering from common cold is infected by common cold virus. When the person suffering from common cold sneezes, fine droplets of moisture carrying thousands of common cold viruses are spread in the air around him. When a healthy person breathes in this contaminated air containing common cold virus, the virus enters his body and he also gets common cold disease.

The communicable diseases can occur and spread in the following ways:

1) By breathing of of air containing micro-organism

2) By taking infected food or water

3) Through insect bites

4) By sharing infected needles

5) By physical contact with an infected person

Other Notes from Chapter 2 Micro Organisms Friend and Foe

• Micro-Organisms
• Groups of Micro Organism
• Where do Micro Organism Live
• Useful Micro organism
• Making of Curd and Bread
• Commercial Use of Micro organism
• Medicinal Use of Micro oragnaism
• Increasing Soil Fertility
• Cleaning the Environment
• Carriers of Disease causing micro organism
• Disease Causing Micro organisms in Animals
• Disease Causing Micro-Organism in Plants
• Food poisoning
• Preservation of Food
• Preservation by sun-drying, Heating, Cooling
• Preservation by Deep Freezing,Common Salt, Sugar
• Preservation of food by mustard oil and Vinegar, Chemicals, Pasteurisation, Air-tight Packets
• Nitrogen Fixation
• Nitrogen Cycle