Subject

Biology

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

21.

(a) Name any two places where it is essential to install electrostatic percipitators. Why is it required to do so?

(b) Mention one limitation of the electrostatic precipitator.

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22.

Prior to a sports event blood and urine samples of sports-persons are collected for drug tests.
(a) Why is there a need to conduct such tests/
(b) Name the drugs the authorities usually look for.
(c) Write the generic names of two plants from which these drugs are obtained.

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23.

Given below is a list of six micro-organism. State their usefulness to humans.
(a) Nucleopolyhedrovirus
(b) Saccharomyces cervisiae
(c) Monascus purpureus
(d) Trichoderma polysporum
(e) Peniciliu notatum.
(f) Propionibacterium sharmanni


The usefulness of various micro-organisms to humans - :

(a) Nucleopolyhedrovirus - It is a biological control agent and is used as a species-specific insecticide.

(b) Saccharomyces cerevisiae - It is used to ferment bread dough.
It is used in the preparation of ethanol by fermenting fruit juices and cereals.

(c) Monascuspurpureus - Statins produced by it work as blood cholesterol lowering agents.

(d) Trichoderma polysporum - It produces cyclosporin A, which is used as an immunosuppressant.

(e) Penicillium notatum - It is a source of penicillin, an antibiotic.

(f) Propionibacterium sharmanii - It helps in the ripening of swiss cheese. It produces large amount of CO2 and thus is responsible for the appearance of large holes in the cheese.

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24.

Reproductive and Child Healthcare (RCH) programmes are currently in operation. One of the major tasks of these programmes is to create awareness amongst people about the wide range of reproduction related aspects. As this is important and essential for building a reproductively healthy society.

(a) Providing sex education in schools in one of the ways to meet this goal. Give four points in support of your opinion regarding this statement.

(b) List any two 'indicators' that indicate a reproductively healthy society.

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25.

Describe the experiment that helped demonstrate the semi-conservative mode of DNA replication

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 Multiple Choice QuestionsLong Answer Type

26.

(a) Explain the post-pollination events leading to seed production in angiosperms.

(b) List the different types of pollination depending upon the source of pollen grains.

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27.

(a) Briefly explain the events of fertilisation and implantation in an adult human female.

(b) Comment on the role of placenta as an endocrine gland.

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28.

(a) How are the following formed and involved in DNA packaging in a nucleus of a cell?

(b) Differentiate between Euchromatin and Heterochromatin

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29.

(a) Why should we conserve biodiversity? How can we do it?

(b) Explain the importance of biodiversity hot-spots and sacred groves.

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30.

(a) Represent diagrammatically three kinds of age-pyramids for the human population.

(b) How does an age pyramid for human population at given point of time helps the policy makers in planning for the future.

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