Ncert exemplar solutions science class 8 Solutions for Chapter 2 microorganisms friend and foe

State TRUE or FALSE:

The process of converting atmospheric nitrogen into usable nitrogen compounds in soil is called Nitrogen fixation.

A disease in human beings caused by virus is _______.

The breakdown of constituents that is carried out by the action of microorganisms and worms and is called …………………………………..

(decomposition/ nitrification)

The disease caused by a protozoan and spread by an insect is _________.

Rhizobium is a bacteria which live in the nodules of roots and fix nitrogen for the plants.

Such a type of relationship between two organisms where both of them benefit from each other is called ………………………. relationship.

(symbiotic/parasitic)

Which of the following reproduces only inside a host cell?

Which of the following gas is released during the preparation of bread?

Which of the following is an air-borne disease caused by a bacterium?

The image below shows a special type of ‘Y’ shaped proteins found in our body, which fights against the disease-causing microorganisms:

What is the name of this ‘Y’ shaped protein?

(Antibody/Antibiotic)

The process by which yeast helps in the conversion of sugars into alcohol is called ………………………………………… This process is used in alcohol and bread making.

(fermentation/drying)

The image below shows a leguminous plant with root nodules:

Which of the following is the nitrogen-fixing micro-organism present in the roots of leguminous plants?

A ………………………………….. is a dead or weakened microorganism that is artificially introduced into the body for developing immunity against the actual infection.

(vaccine/antibody)

…………………………. is a type of fungus used in breads and cakes to make them fluffy.

The process by which milk is first heated and then refrigerated to kill micro-organisms is called ………………………………………..

(pasteurisation /fermentation)

In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?

(Carbohydrate/Nitrogen)

State TRUE or FALSE:

While coughing, one should always cover their mouth to prevent the spread of air brone disease.

Due to which of the following reasons oil is added in the pickles?

Match the microorganisms given in the Column A to the group to which they belong in Column B.

Read the statements given below:

STATEMENT A: Yeast is used for the production of beard and wine.

STATEMENT B: Bread moulds increase the nutrition content of bread.

Which of the above statement is CORRECT?

(A/B)

While returning from the school, Suresh ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill.

Which of the following could be the reason for this?

State TRUE or FALSE:

A virus can reproduce only when it is inside the host cell.

The image below shows the yellow vein mosaic disease caused in plants:

How does this disease spread in the plants?

Yeast ferments sugar to convert it to ………………………………… and carbon-di-oxide gas is released.

(alcohol/oxygen)

The image below shows the micro-organism present in the curd:

Which of the following options correctly gives the name of the micro-organism and its group?

State TRUE or FALSE:

In order to increase the fertility of the soil, farmers prefer to grow leguminous plants rather than other plants.

Due to which of the following reasons fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling?

State TRUE or FALSE:

Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.