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 does industrial melanism support Darwin’s theory of Natural Selection? Explain.
919 Views

22. List the salient features of double helix structure of DNA. 
1029 Views

23. How are the structural genes activated in the lac operon in E.coli
910 Views

Advertisement

24. Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles. 


Plasmodium (malarial parasite) requires two hosts – human and mosquitoes to complete its life cycle. Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs leads to release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days. When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. The parasites multiply within the mosquito’s body to form sporozoites that are stored in their salivary glands. When these mosquitoes bite a human, the sporozoites are introduced into his/her body, thereby initiating the another cycle.


485 Views

Advertisement
Advertisement
25.

(a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.

(b) Name the vector used for introducing the nematode specific gene in tobacco plant.
680 Views

26.

(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.

(b) What is the phenotype of the following:

(i) IAi

(ii) i i

830 Views

27.

(a) List any three ways of measuring population density of a habitat.

(b) Mention the essential information that can be obtained by studying the population of an organism. 
1044 Views

28. How is the amplification of a gene sample of interest carried out using Polymerase Chain Reaction (PCR)? 
707 Views

Advertisement
29.

(a) What is the programme called that is involved in improving success rate of production of desired hybrid and herd size of cattle?

(b) Explain the method used for carrying this programme for cows. 
534 Views

 Multiple Choice QuestionsLong Answer Type

30.

(a) Explain the significance of ecological pyramids with the help of an example.

(b) Why are the pyramids referred to as upright or inverted?
3984 Views

Advertisement