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.

Why are angiosperm anthers called dithecous? Describe the structure of its microsporangium

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22.

If implementation of better techniques and new strategies are required to provide more efficient care and assistance to people, then why is there a statutory ban on amniocentesis? Write the use of this technique and give reason to justify.

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23.

Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.

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24.

Identify ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in the table given below :

No.

Syndrome

Cause

Characteristic of affected individuals

Sex

Male/Female/ both

1

Down’s

Trisomy of 21 chromosome

‘a’ (i)

    (ii)

‘b’

2

‘c’

XXY

Overall masculine development

‘d’

3

Turner

45 with XO

‘e’ (i)

    (ii)

‘f’

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25.

Community Service department of your school plan a visit to a slum area near the school with an objective to educate the slum dwellers with respect to health and hygiene.

(a)Why is there a need to organize such visits?

(b)Write the steps you will highlight, as a member of this department, in your interaction with them to enable them to lead a healthy life.
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26.

The following graph shows the species – area relationship. Answer the following questions as directed

 

(a) Name the naturalist who studied the kind of relationship shown in the graph. Write the observations made by him.

(b) Write the situations as discovered by the ecologists when the value of ‘Z’ (slope of the line) lies between (i) 0.1 and 0.2 (ii) 0.6 and 1.2 What does ‘Z’ stand for ?

(c) When would the slope of the line ‘b’ become steeper ?


(a) Alexander Von Humboldt. He observed that within a region species richness increased with increasing explored area but only up to a limit.

(b)
(i) The slopes of regression lines are similar/ unaffected distribution in an area/ normal range.
(ii) The slope of regression is steeper when we analyze the species-area relationship among very large areas like entire continent.

.Z(slope of the line) is the  regression co-efficient.

(c) If species richness is more/ 0.62-1.2

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27.

Name and describe the technique that helps in separating the DNA fragments formed by the use of restriction endonuclease.

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28.

State the function of a reservoir in a nutrient cycle. Explain the simplified model of carbon cycle in nature.

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29.

Since the origin of life on the earth, there were five episodes of mass extinction of species.

(i)How is the 'Sixth Extinction', presently in progress, different from the previous episodes?

(ii)Who is mainly responsible for the 'Sixth Extinction''?

(iii)List any four points that can help to overcome this disaster.

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 Multiple Choice QuestionsLong Answer Type

30.

(a) Where does fertilization occur in human ? Explain the events that occur during this process.

(b) A couple where both husband and wife are producing functional gametes, but the wife is still unable to conceive, is seeking medical aid. Describe any one method that you can suggest to this couple to become happy parents.
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