CBSE Set Q Biology Sample Test Papers For Class 12th for students online

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Biology Class-Xll  (CBSE)
You are on questions of Section A,B,C,D

Max Marks : 70
Time allowed : 3 hrs

Section A

Question Nos. 1-8 are of very short answer type carrying 1 mark each only. Answer them in 1-20 words each.

Q1. What induces parthenocarpy in grapes?

Q2. What is the term used for the regions of a gene which become part of mRNA and code for the different regions of the proteins?

Q3. The venous blood in the lung has a PCO2 of 46 mm Hg. Should the alveolar PCO2 exceed or be less than 46 mm Hg to result in diffusion of CO2 from the blood into the alveolus?

Q4. Which part of the plant leaf is modified to form spines of Acacia and the sheath covering the leaf of Ficus elastica.

Q5. Name the enzyme that can break and reseal one strand of DNA.

Q6. What does the J-shaped growth curve of a population indicate?

Q7. What forms the cambial ring in a dicot stem during the secondary growth?

Q8. Name the principal mineral anion in the extracellular fluid.

Section B

Question Nos. 9 18 are short answer questions carrying 2 marks each. It is appropriate to answer them in about 20 30 words.

Q9. A mother with O type blood group has conceived. The expected blood group of the foetus is B. Will there be any problems to the mother or the foetus? If so, specify the problems?

Q10. What are the two types of fibres of the connective tissue? Differentiate between the two.

Q11. A farmer observed drops of water along the margins of leaves of tomato plants growing in his well-irrigated field on a winter morning. Give reasons for this occurrence. Why had the water drops appeared only along the leaf margins?

Q12. Give the scientific name of modern wheat. Why is it quoted as a typical example of rapid speciation?

Q13. Name any two of cyanobacteria and explain how they serve as main sources of bio-fertilisers.

Q14. What are the two striking observations when different stages of embryos of different classes of vertebrates are studied comparatively? How does this study support evolution?

Q15. (I) An animal should possess at least one out of the three possible characteristics to enable it to function as a ureotelic organism. List these characteristics.

(II) Which among the following is / are ureotelic animals :
Whale, camel, toad, shark.

Q16. Pick out the plant with whorled arrangement of leaves from the list given below and say why it is categorised so :
Neem; Nerium; Nepenthes.


Q17. How is elongation carried on during protein synthesis in a cell?

Q18. What category of pathogens causes poliomyelitis? How is crippling caused in the victim of this disease? How can this disease be prevented?

Section C

Question Nos. 19 27 are short answer questions carrying 3 marks each. It is appropriate to answer them in about 30 50 words.

Q19. To which category of cells do B-cells and T-cells belong? How do they differ from each other with reference to their formation and response to antigens?

Q20. How did Urey and Miller provide the conditions of primitive earth to prove the origin of life in their experiment?

Q21. Human skin colour is believed to be controlled by at least three separate genes.What do you call this type of inheritance?

  1. Suppose the gene are designated as A, B, and C and darkness is dominant over fairness, what shall be the genotypes of the darkest, fairest and intermediate skin colour?

  2. What will be the total number of allele combinations in the gametes of a person heterozygous, all the three genes.

Q22. Draw a labelled diagram of the vertical section of human heart and show the pulmonary circulation in it by means of arrows.

Q23. Expand PEP. Where is it produced in C4 plants? What is its role in the biosynthetic process?

Q24. What type of striated muscles constitute the muscles of the eyeball? How is this specific type of muscle advantageous?

Q25. The base sequence on one of the strands of DNA is TACTAGGAT.
(i) Write the base sequence of its complimentary strand.
(ii) What is the distance maintained between the two consecutive paired bases in the DNA molecule?
(iii) Who contributed the base complementarity rule?

Q26. Name the parasympathetic nerve from the brain that innervates most of the visceral organs. List any four functions of this nerve.

Q27. Sometimes natural selection is not operative if the abnormal allele is somewhat advantageous to the individual. Explain this mechanism with a suitable example.

Section D

Question. Nos. 28 30 are long answer questions carrying 5 marks each. It is appropriate to answer them in about 80 120 words each.

Q28. What develops into a microspore mother cell in a flower? Trace the development of the cell into a pollen grain, which is ready for germination. Draw a labelled figure of a mature pollen grain.

Q29. What envelops the mammalian ovum preventing the entry of sperm into it easily? How does the sperm gain the entry eventually? What is the significance of the point of entry of the sperm?

Q30. Who demonstrated the semi conservative replication of DNA? Explain the experiment in detail.