Harmful Microorganism Science For Class 8th

Many Microorganisms are harmful to human beings ,plants and animals

  • Some may Cause diseases in Humans
  • Spoil food clothing and leather

Disease causing Microorganisms and virus

  • Disease causing microorganisms enter our body where they multiply damage the body cells and cause disease.

Disease causing microorganisms are called pathogenic microorganisms or simply called pathogens

Pathogens disrupt the normal functioning of the body by attacking different parts of the body.

Disease causing microorganims enters our body through

  • Food , water and air
  • Cuts inĀ  the skin or through direct contact
  • Carriers such as mosqitous and flies

Communicable Diseases

  • Diseases which can transmit from one organism to other through direct contact is called communicable or infetitos desease
  • Tubercolosis,cholera ,Typhoid,Malaria,dysentry are some of the common communicabke diseses
  • Communicable diseases are transmited through contaminated food water air insects infeccted cloths,utensils etc.


Modes Of transmission of communicble diseases

  • Direct Transmission
  • Indirect Transmission

Diect Transmission

The infection may be caused by direct skin to skin contact,Mucosa to mucosa or mucosa to ski contact

Example – leprosy,Eczema, Conjunctivitie( Eye infection)

By Droplet Infections

  • An Infected person during caughing ,sneezing ,spiiting and speaking may release droplets of moisture carrying the disease causing microorganism. Thse sdroplets when enter another persons body while brathing may make him sick
  • Disease like whooping cough TB are transmitted by this way.

By using infected needleor syringe-

  • Infection may also get directly transmitted through a bite or blood transfusion
  • Example- rabies virus anters man’s body through dog bite
  • Aids virus transmitted through infetcted syringe

Indirect Transmission

  • The disease causing microorganism may also enter the persons body indirectly
  • Through infected food and water
  • Through any carrier such as mosqitoes,housefly rat,flea etc.
  • Through clothes , Towels,personal handcerchiefs , Utensils etc.
  • Through dirty hands or dirty/unwashed vegetables

Spread of diseases by insects

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