Bacteria- Microorganisms : Friend and foe Class 8 NCERT Notes

Bacteria cell Structure class 8 ncert notes

Bacteria:-

Bacteria cell Structure class 8 ncert notes
Bacterial cell

Describe or Explain the Structure of Bacteria?)

Structure of Bacteria 

  • Bacteria are single celled or unicellular organism.
  • Their cell structure is unique in that they don’t have nucleus.
  • Its nucleic material lies unprotected cytoplasm without the nuclear membrane.
  • Most organelles of bacteria don’t have organelle membrane.
  • Their chromosomes composed of a single closed DNA circle.
  • Most bacteria have cell walls.
  • Some bacteria survive adverse condition by forming spore a cyst.
  • Bacteria may occur as single cell, pair or chain of cells.
  • Some bacteria’s also occur as cluster of 4 or many cells.

Also Check -Microorganisms : Friend and foe Class 8 NCERT Notes 

Shape of bacteria

Bacteria are found in three different shapes

  • Rod shaped, called bacilli
  • Spherical shaped, called cocci
  • Spiral shape, called spirilla
  • Comma shaped ,  called vibrios.
bacteria in diffrent shapes Class 8 NCERT notes
Diffrent Shapes Of Bacteria

Habitat of bacteria

  • Bacteria can survive almost all living conditions.
  • They are found everywhere: – in soil, water, air, sewage, snow, hot Springs and so on.
  • Ideally Bacteria thrive in moisture and a temperature of 30-37 degree Celsius.
  • Some bacteria survive adverse condition by forming a spore a cyst (Fmodeective coating).
  • When the environment improves the come to life again and begin multiplying.
  • Bacteria also lives on surface of human body animals.
  • Millions of Bacteria also live in alimentary canal of animals including man.

Mode of nutrition in bacteria /  How bacteria feed themselves??

Most bacteria are heterotrophs and may lead a saprophytic for parasitic existence.

Heterotrophs— organisms which depends upon other organisms to survive all animals and non-green plants are heterotrophic.

Saprophytic—  is a mode of heterotrophic nutrition, in this mode of nutrition the organism obtain their food from dead and decaying organic matter half dead plants animals and other decomposing organic matter.
Parasitic nutrition— it is also heterotrophic mode of nutrition in which parasitic organism lives on the body surface or the body of another type of organism and gets nutrition directly from the body of the host).

  • Some bacteria are commensals, which lives in a host body and benefit from it without harming or helping the host.
  • Some bacteria make their own food by process resembling photosynthesis.

How do Bacteria Reproduce? What is the mode of Reproduction in Bacteria?

Reproduction in bacteria 

Microorganisms :Friend and foe class 8 notes
Reproduction in Bacteria
  • Bacteria reproduce by cell division, the single cell giving rise to two cells.
  • Lifespan of bacteria is just 15 to 20 minutes. Given favorable environment bacteria multiply so rapidly that one bacterium can give rise to millions within 24 hours.

What are the uses or benefits of Bacteria?Usage or Benefits of the Bacteria

  • Bacteria are useful and help in making foods like curd.
  • Bacterias are also used in fermentation industry.
  • Some nitrogen fixing bacterias are useful in plants growth.
  • Bacteria decomposes waste organic matter.
  • Some bacterias also causes diseases. For examples  diseases caused by bacteria are cholera, typhoid, tuberculosis, diphtheria, whooping cough and food poisoning.

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