Q23 of 28 Page 10

How do vaccines work?

A vaccine is a preparation of killed or weakened disease-causing microbes and when it is introduced into the body of a healthy person, the body produces antibodies against these microbes. These antibodies remain in the body and protect us from infections in the future caused by the same microbes.


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21

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

(b) Write one important characteristic of the virus.

 22

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


(a) Write the names 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.

 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?