Q28 of 28 Page 10

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

a) Lightning fixes atmospheric nitrogen.


b) Nitrogen-fixing bacteria and blue-green algae fix atmospheric nitrogen.


c) Nitrogenous waste from excretion by animals and plants and decomposition of dead plants and animals.


d) Nitrogen released by bacteria from nitrogenous compounds present in soil into air.


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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?


 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?

 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 refrigerator 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 through they do not live in water. Why?

 27

How can we prevent the following diseases?

(a) Cholera


(b) Typhoid


(c) Hepatitis A