ICSE Worksheet for Chapter - 3 Microorganisms: Friend and Foe Class 8

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Find ICSE Worksheet for chapter-3 Microorganisms: Friend and Foe class 8

CLASS-8

BOARD: ICSE

BIOLOGY Worksheet - 3

TOPIC: Microorganisms: Friend and Foe

For other ICSE Worksheet for class 8 Science check out main page of Physics Wallah.

1. Fill in the blanks:

(a) Cholera is caused by ___________.

(b) Blue green algae fix ___________ directly from air to enhance fertility of soil.

2. Match the organisms in Column A with their action in Column B :

       A                            B

(i) Bacteria            (a) Fixing nitrogen

(ii) Rhizobium       (b) Setting of curd

(iii) Lactobacillus  (c) Baking of bread

(iv) Yeast              (d) Causing malaria

(v) A protozoan    (c) Causing cholera

(vi) A virus            (f) Causing AIDS

                             (g) Producing antibodies

3. Which one of the following sets includes the bacterial diseases?

(a) Cholera, typhoid, mumps

(b) Tetanus, Tuberculosis, Measles

(c) Malaria, typhoid, chicken pox

(d) Diptheria, typhoid, tuberculosis

4. Amoebic dysentery is transmitted by

(a) Sneezing

(b) Using contaminated water

(c) Direct contact

(d) Mosquito

5. Anthrax in cattle is caused by

(a) Fungi

(b) Virus

(c) Bacteria

(d) Algae

6. Carrier of malaria-causing protozoan is

(a) Female Anopheles mosquito

(b) Cockroach

(c) Housefly

(d) Butterfly

7. How does our body fights when a disease carrying microbe enters our body?

8. Some microorganisms live in the roots of leguminous plants. Are they harmful or useful to plants and why?

9. What are preservatives? Name two common preservatives used to preserve jams and pickles.

10. Write a short paragraph on the harms caused by microorganisms.

Solutions: to worksheet-3 Topic- Microorganisms: Friend and Foe

1. (a) Vibrio cholerae

(b) nitrogen

2. (i) e

(ii) a

(iii) b

(iv) v

(v) d

(vi) f

3. (d) Diptheria, typhoid, tuberculosis

4. (b) Using contaminated water

5. (c) Bacteria

6. (a) Female Anopheles mosquito

7. When a disease carrying microbe enters our body, the antibodies present in our cells detect it and gets activated. Once activated these acts as a defense mechanism and protects our body from its transmission. This is called natural immunity.

8. The microorganisms like Rhizobium, Azotobacter living in the root nodules of leguminous plants are useful to plants and soil. These microbes form symbiotic association by fixing atmospheric nitrogen and converting it into nitrates and nitrites which are useful nutrients for plant growth.

9. Preservatives are the substances added to the food in order to maintain its taste and quality for a longer period of time. Sugar is commonly added to preserve jams, and oil and salt is added to presence pickle.

10. Micro-organisms causing diseases in plants, animals and humans are termed as pathogens. The harms caused by these microbes are as follows:

(i) Bacteria like Vibrio cholerae and Salmonella typhi causes disease like cholera and typhoid respectively.

(ii) Also diseases like pneumonia and tuberculosis is caused by bacteria Streptococcus pneumonae and Mycobacterium species.

(iii) Female Anopheles mosquito is a carries for malarial parasite Plasmodium and female Aedes mosquito carries dengue virus causing dengue fever.

(iv) Bacillus anthracis causes anthrax which a dangerous disease for humans as well as cattles.

(v) Canker is caused in citrus fruits due to bacteria.

(vi) Yellow vein mosaic disease is caused in okra (bhindi) by virus transmitted through insect.

(vii) Serious diseases caused by viruses are chicken pox, jaundice, AIDS. SARS, Herpes, swine flu, mumps, polio etc.