Activity Answer Microorganisms Friend or foe

Activity Answer Microorganisms Friend or foe Chapter 2 Class 8 Science

Activity 2.1Activity 2.1 class 8 science

This activity asks us to make a microscopic slide of organisms present in soil and observe it under the microscope.

Procedure:

  • Put some soil in a test-tube
  • Add some water in it
  • Shake the test tube and allow it to settle.
  • pick up a  drop of water using a pipette and put it into the slide.
  • put the coverslip on the slide
  • observe it under a simple microscope.

Observation:

We see numerous organisms moving inside the slide.

Explanation:

Soil is a natural harbour of microorganisms. Many organisms live there. It becomes visible when we observe it under a microscope. Above is a  sample of soil under a microscope. There are many organisms. Those with tail swim and those who do not have tails are non-motile.

The moving organism here is Chlamydomonas.

Inference:

Soil is home to many microorganisms. Always wash your hand properly with soap after you come in contact with the oil.

Activity 2.2Activity Answer Microorganisms Friend or foe Chapter 2 Class 8 Science

Activity 2.2 asks us to see the slide of pond water just like we did in activity 2.1.

Observation:

We see numerous green filamentous organism along with other organisms.

Explanation:

Pond water is stagnant water. It harbours many microorganisms just like the soil.

Here a green filamentous fungi spirogyra is common.

Inference: Pond water contains numerous microorganisms.

Activity 2.2Activity 2.3 class 8 science

Activity 2.2 asks us to add some yeast to atta or maida.

Procedure:

  • Take lukewarm water.
  • Add a spoonful of sugar.
  • Add some yeast to the solution.
  • mix the solution with the flour.
  • wait for a 2 hour.

Observation:

Flour swells and increases its size like a balloon.

Explanation:

Activity 6.5 NCERT class 10 science
Yeast raises the dough.

Yeast is a microorganism. It usage sugar to multiply in number and produces carbon dioxide gas. This gas gets trapped into the floor. As a result, dough raises.

Inference:

Dough and sugar act as a food source to microorganisms.

Facts:

Bakes raised dough is soft and crispier. So, Bakery shop uses this in making bread, pizza base, cakes etc.

Activity 2.4Activity 2.4 class 8 Science

Activity 2.4 asks us to add some yeast sugar solution and observe the smell after a few hours.

Observation:

We see foul smell coming from the solution. The solution looks pale and untidy.

Explanation:

Sugar acts as a food source to yeast. Yeast decomposes it and forms alcohol and carbon dioxide through the process called Fermentation.

As a result, the solution smells.

Inference:

Yeast fermentate sugar and produces alcohol.

Application:

Fermentation is a widely used application in the food industry. Pickles, vinegar, dosa batter are products of fermentation.

See also: Activity solution Chapter 1.

Microorganisms Friend or foe MCQ

 

Activity Answer Microorganisms Friend or foe Chapter 2 Class 8 Science

 

Ref: Ch2.

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