NCERT Solutions For Class 8 Science Chapter 2 Microorganisms Friend And Foe LAQs

NCERT Solutions For Class 8 Science Chapter 2 Long Answer Questions

Question 1. Manoj adds some yeast to two test tubes containing sugar solution. He ties balloons on the mouth of each of the test tubes. One test tube is kept in ice and the other at room temperature. The picture shows what happens after three hours.

1. What In Manoj Invontignting?

1. Does yeast grow in sugar solution only?
2. Does yeast convert sugar into alcohol?
3. Does temperature affect the growth of yeast?
4. Which gas is produced as yeast grows in a sugar solution?

Answer: 3. Does temperature affect the growth of yeast?

NCERT Class 8 Science Chapter 2 Microorganisms LAQs

2. How can Manoj confirm, If the gas produced In the tost tube at room temporaturo was due to tho yeast growing In It?

1. He should repeat the same experiment
2. He should leave the test tube undisturbed for six hours
3. He should repeat the experiment with test tubes containing more sugar solution
4. He should keep an extra set of test tubes with sugar solution, but without the yeast

Answer: 4. He should keep an extra set of test tubes with sugar solution without the yeast

3. What should Manoj keep the same in both the test tubes for a fair experiment? Circle ‘Yes’ or ‘No’ for each row.

Answer:

1. Yes
2. No
3. Yes

4. What type of organism is yeast?

1. Fungi
2. Algae
3. Bacteria
4. Protozoa

Answer: 1 Fungi

NCERT Solutions for Microorganisms Friend and Foe LAQs

Question 2. How can we prevent the following diseases?

1. Cholera
Answer: Cholera. By maintaining personal hygiene and good sanitation practices.

2. Typhoid
Answer: Typhoid. By eating properly cooked food, drinking boiled water, and getting vaccinated against the disease.

3. Hepatitis-A
Answer: Hepatitis. By drinking boiled water and getting vaccinated against the disease.

NCERT Solutions for Class 8 Science Microorganisms LAQs

Question 3. Give reasons for the following.

1. Fresh milk is boiled before consumption, while processed milk is stored in packets and can be consumed without boiling.
Answer: Fresh milk is boiled before consumption to kill the microorganisms in it. But packed milk is pasteurised and does not contain any microorganisms. Thus, it can be consumed without boiling.

2. Raw vegetables and fruits are kept in refrigerators, whereas jams and pickles can be kept outside.
Answer: Raw vegetables and fruits get easily infected by microorganisms and get spoiled. They are kept in the refrigerator at a low temperature inhibits the growth of microbes. Jams and pickles contain sugar and salt as preservatives. They do not get infected by microbes, as these preservatives do not allow the growth of microbes.

NCERT Class 8 Microorganisms Friend and Foe LAQs

3. Farmers prefer to grow beans and peas in nitrogen-deficient soils.
Answer: Beans and peas are leguminous plants and have Rhizobium in their root nodules. These bacteria can fix atmospheric nitrogen to enrich the soil with nitrogen and increase its fertility.

4. Mosquitoes can be controlled by preventing stagnation of water, though they do not live in water. Why?
Answer: Though mosquitoes live on land, their larvae grow in water. If water stagnation is prevented, their larvae cannot survive, thus reducing the mosquito population