List of top Biology Questions asked in CBSE CLASS XII

How do biofertilisers enrich the fertility of the soil?
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd

Find out the role of microbes in the following and discuss it with your teacher.

(a) Single cell protein(SCP)
(b) Soil

Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.

Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
Do you think microbes can also be used as source of energy? If yes,how?
What is sewage? In which way can sewage be harmful to us?
Name any two species of fungus which are used in the production of the antibiotics.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Name some traditional Indian foods made of wheat rice and bengal gram (or their products) which involve use of microbes.
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Give examples to prove that microbes release gases during metabolism.
Bacteria cannot be seen with the nacked eyes but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence have microbes under a microscope which sample would you carry and why?
In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
Why is that once a person starts taking alcohol or drugs it is difficult to get rid of this habit? Discuss it with your teacher.
Do you think that friends can influence one to take alcohol/drugs? If yes how may one protect himself/herself from such an influence?
List the harmful effects caused by alcohol/drug abuse.
Explain what is meant by metastasis.
What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?

What are the various routes by which transmission of human immunodeficiency virus takes place?

Differentiate the following and give examples of each:
(a) Innate and acquired immunity
(b) Active and passive immunity

The following are some well-known abbreviations which have been used in this chapter. Expand each one to its full form:
(a) MALT
(b) CMI
(c) AIDS
(d) NACO
(e) HIV

Name the primary and secondary lymphoid organs.
Discuss with your teacher what does 'a suitable gene' means in the context of DNA vaccines.