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8th Standard CBSE Science Unit 1 Microorganisms Friend and Foe Important Question Paper | QB365

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8th Standard CBSE Science Unit 1 Microorganisms Friend and Foe Important Question Paper

Published on: 26/07/2019

Microorganisms Friend and Foe

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Std: 8th Standard CBSE - Science

chapter: - Model Question paper

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Questions:

Multiple Choice Question

10 x 1 = 10

Nitrogen fixation is brought about by :

(a)

blue-green algae

(b)

bacteria

(c)

both (a) and (b)

(d)

none of these

Edward Jenner discovered:

(a)

fermentation

(b)

antibiotics

(c)

vaccine

(d)

none of these

This micro-organism is used for the large-scale production of alcohol, wine and acetic acid:

(a)

amoeba

(b)

paramecium

(c)

chlamydomonas

(d)

yeast

This bacterium promotes the formation of milk into curd:

(a)

rhizobium

(b)

lactobacillus

(c)

aedes

(d)

all

Typhoid is a ________ disease.

(a)

protozoan

(b)

viral

(c)

bacterial

(d)

fungi

The bread or idli dough rises because of

(a)

heat

(b)

grinding

(c)

growth of yeast cells

(d)

kneading

The most common carrier of communicable diseases is

(a)

ant

(b)

housefly

(c)

dragonfly

(d)

spider

Carrier of malaria-causing protozoan is

(a)

female Anopheles mosquito

(b)

cockroach

(c)

housefly

(d)

butterfly

The following is an antibiotic

(a)

sodium bicarbonate

(b)

streptomycin

(c)

alcohol

(d)

yeast

10.

Yeast is used in the production of

(a)

sugar

(b)

alcohol

(c)

hydrochloric acid

(d)

oxygen

Match the following

5 x 1 = 5

11.

Hot and cold treatment

12.

Hepatitis A

13.

Aspergillus

14.

Lactobacillus

15.

A virus

Generic 3

3 x 3 = 9

16.

Who discovered the bacterium Bacillus anthracis? Which disease can be caused by it? Is it harmful?

17.

Write a short paragraph on the harmful effects of microorganisms.

18.

Name the microorganisms which can fix atmospheric nitrogen in the soil.

Generic 2

5 x 2 = 10

19.

Who discovered the first antibiotic? Name any two antibiotics.

20.

How are micro-organisms useful for commercial productions?

21.

Name the process in yeast that converts sugars into alcohol.

22.

Write the name of two groups of microorganisms which live in colonies.

23.

Mention a characteristic of viruses

Generic 5

2 x 5 = 10

24.

What are food preservatives? Explain some common food preservatives.

25.

Give causative microorganism, mode of transmission and one preventive measure Qf human diseases like Polio, Cholera and Hepatitis-B.

Fill up / 1 Marks

5 x 1 = 5

26.

Carriers of specific microorganisms are called ___________________

27.

Paramecium is a slipper- shaped ___________________

28.

______________ is a nitrogen fixing bacteria.

29.

Pathogens are___________ causing organisms.

30.

Under unfavourable conditions, microorganisms form a _______________ around themselves.

True or False

5 x 1 = 5

31.

Jams, jellies and squashes are preserved by adding salt.

(a)

True

(b)

False

32.

Protozoa cause diseases like dysentery and malaria.

(a)

False

(b)

True

33.

Microorganisms can be found only in air and water.

(a)

True

(b)

False

34.

Foot and mouth disease is a bacterial disease in animals.

(a)

True

(b)

False

35.

Edward Jenner discovered the process of fermentation.

(a)

True

(b)

False

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Answers Key:

Multiple Choice Question

10 x 1 = 10

(d)
yeast

(b)
lactobacillus

(b)
housefly

(a)
female Anopheles mosquito

(b)
streptomycin

10.

(b)
alcohol

Match the following

5 x 1 = 5

11.

()
Pasteurization

12.

()
Virus fixers

13.

()
Fungi

14.

()
Bacteria

15.

()
Causing AIDS

Generic 3

3 x 3 = 9

16.

Robert Koch (1876) discovered the bacterium Bacillus anthracis, which causes anthrax disease. It is dangerous for humans and cattle both.

17.

Microorganisms are harmful for human beings in many ways. They cause diseases in humans, plants and animals, e.g.
(i) In humans, bacteria cause diseases such as cholera, typhoid, tuberculosis, etc.
(ii) In cattle, the foot and mouth disease is caused by a virus.
(iii) Also several microbes cause diseases in plants, e.g. tikka disease, late blight of potato. Some microbes grow on food and secrete toxic substances which make the food poisonous.

18.

Bacteria such as Rhizobium and certain blue-green algae (Anabaena, Nostoc) present in the soil can fix atmospheric nitrogen and convert it into usable nitrogenous compounds.

Generic 2

5 x 2 = 10

19.

Alexander Fleming discovered first antibiotic penicillin. Two other common antibiotics are streptomycin and tetracycline.

20.

Micro-organisms are commercially used for the large scale production of alcohol, wine and acetic acid. Yeast is commonly used for commercial production of wine and alcohol.

21.

Fermentation is the process by which yeast converts sugars into alcohol.

22.

The groups of microorganisms which live in colonies are bacteria and fungi.

23.

Viruses are cellular tiny microscopic organisms that can develop only inside the cells of host organisms.

Generic 5

2 x 5 = 10

24.

The chemical substances which are used to check or stop the growth of harmful micro-organisms in food are called food preservatives. These food preservatives keep the edible food materials protected from the invasion of micro-organisms which can spoil the food. Some common food preservatives are :
(i) Salt: Common salt is used to preserve meat, fish, amla raw mangoes, tamarind, etc.
(ii) Sugar: Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria, that can spoil food.
(iii) Oil: Edible oils are used as preservatives in vegetables and pickles. Oil does not allow the moisture to surface, thus preventing the growth of harmful bacteria.
(iv) Vinegar: It is used to preserve fruits, vegetables, fish, meat and pickles.

25.

Disease	Causative microorganism	Mode of transmission	Preventive measure
Polio	Virus	Air/Water	Vaccination should be given at suitable age
Cholera	Bacteria	Water/Food	Maintain personal hygiene and good sanitary habits.
HepatitisB	Virus	Water	Drink boiled drinking water and proper vaccination should be taken.