Introduction

  • Microorganisms are very small that cannot be even seen by the naked eyes.
  • Fungi, bacteria, algae and protozoa are the four groups of microorganisms.
  • Viruses are also said to be microscopic.

class 8 microorganisms

Where do microorganisms live?

  • Microorganisms have the power to survive in any type of environment.
  • They are also seen inside the body of the other organisms.
  • Amoeba lives alone whereas bacteria and fungi live in colonies.

Microorganisms and us

  • In bread, cake and curd.
  • In the production of alcohol
  • By fixing nitrogen in soil fertility.

class 8 microorganisms

Commercial use of microorganisms

  • For a huge production of wine, alcohol.
  • Used in the production of acetic acid

class 8 microorganisms

Increasing Soil fertility

  • Some blue-green algae and bacteria can increase the fertility of the soil by just fixing the nitrogen from the atmosphere to enrich and enhance the soil with nitrogen
  • Biological nitrogen fixers are the name given to these microbes.

Harmful microorganisms

  • Some cause diseases in humans, animals and plants.
  • They spoil food, leather and clothing also.
  • The diseases caused in humans are cholera, chicken pox, common cold, tuberculosis.
  • The diseases caused in the animals are anthrax, foot and mouth disease of a cattle.
  • The diseases caused in plants are citrus canker, rust of wheat. 

Food poisoning

  • In humans, food poisoning is caused when we consume the spoiled food by some microorganisms.
  • Microorganisms make our food poisonous by producing toxic substances.

Food preservation

  • Chemical methods like using salt and edible oils.
  • Preserving using common salt.
  • Preservation by sugar
  • Preservation by vinegar and oil.
  • Packing and storage.
  • Cold and heat treatments.

 

Recap

  • Microorganisms are very small that cannot be even seen by the naked eyes.
  • Fungi, bacteria, algae and protozoa are the four groups of microorganisms.
  • Microorganisms have the power to survive in any type of environment.
  • In humans, food poisoning is caused when we consume the spoiled food by some microorganisms.
  • Microorganisms make our food poisonous by producing toxic substances.