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.
Advertisement

 Multiple Choice QuestionsShort Answer Type

21. How are dominance, co-dominance and incomplete dominance patterns of inheritance different from each other?
779 Views

22.

The base sequence in one of the strands of DNA is TAGCATGAT.

(i) Give the base sequence of its complementary strand.

(ii) How are these base pairs held together in a DNA molecule?

(iii) Explain the base complementarity rules. Name the scientist who framed this rule.

431 Views

23.

(a) Sickle celled anaemia in humans is a result of point mutation. Explain.

(b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.

588 Views

24. What is inbreeding depression and how is it caused in organisms? Write any two advantages of inbreeding.
490 Views

Advertisement
25.

(a) Identify (A) and (B) illustrations in the following:

i. 



ii. 



(b) Write the term given to (A) and (C) and why?

(c) Expand PCR. Mention its importance in biotechnology.

714 Views

26.


The diagram above is that of a typical biogas plant. Explain the seQ uence of events occurring in a biogas plant. Identify a, b and c.

546 Views

27.

How can crop varieties be made disease resistant to overcome food crisis in India? Explain.

Name one disease resistant variety in India of:

(a) Wheat to leaf and stripe rust

(b) Brassica to white rust

551 Views

Advertisement

28.

Write the source and the effect on the human body of the following drugs:

(i) Morphine

(ii) Cocaine

(iii) Marijuana


The source and effect of the following drugs are:

(i) Morphine:

 Source- latex of poppy plants (Papaver somniferum)

Effect- It is a depressant; slows down body functions

(ii) Cocaine:

Source: Coca plant Erythroxylum coca, found in South America Effect: Stimulates the CNS, producing a sense of euphoria and increased energy; excessive dosages cause hallucination.

(iii) Marijuana:

Source: Inflorescences of the plant Cannabis sativa

Effect: Affects the cardiovascular system.
494 Views

Advertisement
Advertisement
29.

Name the type of interaction seen in each of the following examples:

(i) Ascaris worms living in the intestine of human

(ii) Wasp pollinating fig inflorescence

(iii) Clown fish living among the tentacles of sea-anemone

(iv) Mycorrhizae living on the roots of higher plants

(v) Orchid growing on a branch of a mango tree

(vi) Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland.

451 Views

 Multiple Choice QuestionsLong Answer Type

30.

(a) Draw a labelled diagram of the human female reproductive system. 

(b) Enumerate the events in the ovary of a human female during: 

(i) Follicular phase

(ii) Luteal phase of menstrual cycle

569 Views

Advertisement