Question

NCERT VIII - Sciences

Write a short paragraph on the harms caused by microorganisms.

Answer 1

Microorganisms can be very harmful to us, as they cause a number of human and animal diseases. Diseases in humans like common cold, tuberculosis, measles, chicken pox, polio, cholera, typhoid, hepatitis-B, malaria etc. all are caused by microorganisms. Some serious diseases like- Anthrax is a dangerous human and cattle disease caused by a bacterium. Microbes grow on food products and render them unfit for consumption. Consumption of such food causes food poisoning. Microbes also spoil clothes and leather products. Microorganisms cause diseases of plants like – blights in potatoes, sugarcanes, oranges then, rust of wheat citrus, canker etc. They also reduce the crop yield.

Answer 2

Harmful or Pathogenic MicroorganismsPathogenic means capable of causing disease. An actual harmful effect of a microbe to the body depends on:microbial virulence - a relative ability of a microbe to cause a disease; for example, a certain, higly virulent subtype of influenza virus may cause a bird flu, which is deadly in a high percent, while “usual” influenza virus is not.invasion through the body’s barriers; staph bacteria might not cause any harm to a person with an intact skin, but can cause a severe infection of a skin wound.amount of microbes; eating few bites of food contaminated with staph bacteria may go unnoticed, while eating the whole portion of the same food may cause a severe food poisoning.body’s defense (immune) system; patients with a weak immune system, like those receiving corticosteroids, often get oral thrush (candida infection of the mouth), while otherwise healthy people do not.