Microorganisms Friend And Foe - Worksheets

CBSE Worksheet-01
Class–VIII Science (Microorganisms: Friend and Foe)

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1. Low temperature prevents spoilage of food because it :-
   1. Retards microbial growth
   2. Inactivates enzymes
   3. Both a & b
   4. Removes water from food materials
2. Which of the following is found to be present in curd?
   1. Lactobacillus
   2. Rhizobium
   3. Lactovirus
   4. Lactococcus
3. In the given picture the microbe responsible for the spoilage is a :-
   
   1. Virus
   2. Protozoa
   3. Bacteria
   4. Fungus
4. The microorganism used in preparation of bread is :-
   1. Yeast
   2. Adenovirus
   3. Penicillium
   4. Blue green algae
5. Match the column :-

   Disease	Transmission by
   a. Dengue	i) Infected dog’s bite
   b. Hepatitis B	ii) Contact
   c. Food poisoning	iii) Contaminated water
   d. Rabies	iv) Carrier Aedes mosquito bite
   e. Small Pox	v) Contaminated food

6. Fill in the blanks:-
   1. ______ are preserved by the use of oil and vinegar.
   2. ______ is the process of heat and cold treatment for preserving milk.
   3. ______ is a dangerous form of food poisoning.
   4. ______ is the oldest method of food preservation.
   5. Jellies, squashes and jams are preserved by ______ syrup.
7. How the percentage of nitrogen in the atmosphere remains more or less constant ?
8. Identify the microorganism in the picture and write any one important feature of it?
   
9. Pick the odd word out of the following: -HIV, Cholera, Sleeping sickness, Cancer, Citrus canker.
10. Write the correct words by putting letters in correct sequence-i) ttiiibcoans ii) gotsenpah

CBSE Worksheet-01
Class–VIII Science (Microorganisms: Friend and Foe)
[Answer]

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1. c
2. a
3. d
4. a
5. a. iv, b. iii, c. v, d. i, e. ii.
6. 1. Pickles
   2. Pasteurisation
   3. Botulism
   4. Dehydration
   5. Sugar.
7. Nitrogen present in air is fixed by some microbes known as nitrifying bacteria. The fixed nitrogen is utilised by plants and then by animals. After their death, fixed nitrogen is released back into the atmosphere in its molecular form by the action of another group of microbes called denitrifying bacteria. Due to this cyclic movement the percentage of nitrogen in the atmosphere remains more or less constant.
8. The picture shows a virus of bacteriophage group and they are all parasites on bacteria. They reproduce inside the host cell by utilising the cell machinery of the host and increase their number till the bacterial cell bursts open to release the virus particles.
9. All others are communicable diseases except Cancer.
10. i) antibiotics ii) pathogens