Chapter 2 Microorganisms : Friend And Foe

Question 1. Which of the following reproduces only inside a host cell?

(a) Bacteria

(b) Virus

(c) Amoeba

(d) Fungus.

Question 2. A disease in human beings caused by virus is _______.

(a) typhoid

(b) influenza

(c) dysentry

(d) cholera

Question 3. Pathogenic micro-organisms present in host cells are killed by medicines called

(a) pain killer

(b) antibodies

(c) antibiotics

(d) vaccines

Question 4. The two micro-organisms which live in symbiotic association in lichens are

(a) fungus and protozoa

(b) alga and bacteria

(c) bacteria and protozoa

(d) alga and fungus

Question 5. The gas released during the preparation of bread is

(a) oxygen

(b) carbon dioxide

(c) nitrogen

(d) sulphur dioxide

Question 6. The disease caused by a protozoan and spread by an insect is _________.

(a) dengue

(b) malaria

(c) polio

(d) measles

Question 7. Paheli dug two pits, A and B, in her garden. In pit A, she put a polyhtene bag packed with some agricultural waste. In pit B, she dumped the same kind of waste but without packing it in a polythene bag. She, then covered both the pits with soil. What did she observe after a month?

(a) Waste in pit A degraded faster than that in pit B.

(b) Waste in pit B degraded faster than that in pit A.

(c) Waste in both pits degraded almost equally.

(d) Waste in both pits did not degrade at all.

Question 8. Unscramble the jumbled words underlined in the following statements.

(a) Cells of our body produce santiidobe to fight pathogens.

(b) curbossulite is an air-borne disease caused by a bacterium.

(c) Xanrhat is a dangerous bacterial disease.

(d) Yeasts are used in the wine industry because of their property of meronettinaf.

Question 9. Suggest a suitable word for each of the following statements.

(a) Chemicals added to food to prevent growth of microorganisms.

(b) Nitrogen-fixing microorganism present in the root nodules of legumes.

(c) Agent which spreads pathogens from one place to another.

(d) Chemicals which kill or stop the growth of pathogens.

Question 10. Match the names of scientists given in Column A with the discovery made by them given in Column B.

Question 11. Name one commercial use of yeast.

Question 12. Name the process in yeast that converts sugars into alcohol.

Question 13. In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?

Question 14. Why should we avoid standing close to a tuberculosis patient while he/she is coughing?

Question 15. Polio drops are not given to children suffering from diarrhoea. Why?

Question 16. Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grand mother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?

Question 17. Match the microorganisms given in the Column A to the group to which they belong in Column B.

Question 18. Classify the following into friendly and harmful microorganisms.

Yeast, malarial parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis

Question 19. While returning from the school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?

Question 20. What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?

Question 21. (a) Name two diseases that are caused by virus.

(b) Write one important characteristic of virus.

Question 22. Observe the Fig.2.1 and answer the questions that follows.

(a) Write the name of the disease.

(b) Name the causative agent of this disease?

(c) How does the disease spread from one plant to another?

(d) Name any two plant diseases and the microbes that cause them.

Question 23. How do vaccines work?

Question 24. Observe the set up given in Fig. 2.2 and answer the following questions.

(a) What happens to the sugar solution in A?

(b) Which gas is released in A?

(c) What changes will you observe in B when the released gas passes through it?

Question 25. Observe the Fig.2.3 and answer the following questions.

(a) Name the microorganism and the group to which it belongs.

(b) Name the food item on which the organism grows.

(c) Does it grow well in dry or in moist conditions?

(d) Is it safe to eat infected bread?

Question 26. Give reasons for the following.

(a) Fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling.

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

(c) Farmers prefer to grow beans and peas in nitrogen deficient soils.

(d) Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?

Question 27. How can we prevent the following diseases?

(a) Cholera

(b) Typhoid

(c) Hepatitis A

Question 28. Complete the following cycle given as Fig. 2.4 by filling the blanks (a), (b), (c) (d)