Half Yearly Exam /Pre Board Exam

Class  XII                                                                                                                                                                        M.Marks. : 70

Sub : Biology                                                                                                                                                              Time : 3 Hrs.



General Instructions :

(a)          All questions are compulsory.

(b)         The question paper consists of four sections A,B,C & D. Section A contains 8 questions of 1 mark each, Section B is of 10 questions of 2 marks each, Section C has 9 questions of 3 marks each whereas Section D is of 3 questions of 5 marks each.

(c)          There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and all the three questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.

(d)         Wherever necessary, the diagram drawn should be neat and properly labelled.





Q 1. Name the enzyme used to digest the cell wall of (i) bacteria & (ii) fungi, respectively, for genetic engineering purposes?

Q 2. What is the key difference between primary treatment and secondary treatment of sewage?

Q 3. Expand MTP.

Q 4. Mention the function of reservoir in nutrient cycles?

Q 5. Mention any two significant roles that predation plays in an ecosystem?

Q 6. State the law of Mendel, which explains the appearance of  only one of the parental forms of the trait in the hybrid?

Q 7. What is Elution?

Q 8. Why is FSH administered to a cow in MOET technology?




Q 9.  Write the dual function of the codon AUG?

Q 10.  What is meant by a ‘breed’? What is the objective of animal breeding?

Q 11. What is phenotypic adaptation? Give an example.

Q 12. How does the study of fossils support organic evolution?

Q 13. Fill in the blanks a,b,c & d in the following table/abbreviations of the terms associated with ARTs?

IVF & ET                a

IUI                        b

c                  Introduction of ova of a donor into the fallopian tube

d                 Introduction of Zygote/embryo with 8-blastomeres into the fallopian tube.


Q 14. How are Mendelian disorders different from chromosomal disorders?

Q 15. Name the techniques used to obtain multiple copies of a DNA segment of interest by synthesis in vitro. Name two sets of primers that are necessary for the reaction to occur.


Give reason for the following :

(a)          Insulin cannot be administered orally to a diabetic patient.

(b)         Biopiracy affects India the most.

Q 16. ‘Thermoregulation is more effective in larger animals than is smaller animals. Explain?

Q 17. Mention any four warning signals of drug/alcohol abuse by an adolescent?

Q 18. Differentiate between pioneer community & climax community?




Q 19. What is eutrophication? Mention its consequences?

Q 20. A male child is born with 47 chromosomes. Write any two possible chromosome complement of this child. Name the disorder and one characteristic symptom of each of these disorders?

Q 21. Represent diagrammatically the elongation in translation?

Q 22. Name the accessory glands of human male reproductive system. What is the colletive term given to the secretions of them? Name one sugar and an element it is rich in?

Q 23. What is insertional inactivation? How is it used to distinguish the recombinants from the non-recombinants?

Q 24. Justify the following statements :

(a) Smoking leads to deficiency of oxygen in the body tissues.

(b) Cancer patients are administrated interferons.

(c) Chewing of tobacco causes an increase in blood pressure.

Q 25. (a) Name the category of enzymes that cut at a specific site within the DNA molecule. Give an example.

(b) Explain how these enzymes function mention their use in genetic engineering.

Q 26. (a) What are isogametes?

(b) Mention the condition

(i) When emasculation is necessary and

(ii) When it is not necessary, but bagging is always necessary during hybridisation to produce improved crop variety. Justify?

Q 27. (a) How does the catalytic converter function in an automobile?

(b) The entire fleet and public transport in Delhi is switched over to CNG from petrol/diesel. Why is CNG preferred as a fuel?


(a)          Mention any four strategies to reduce global warming.

(b)         Name the following :

(i) The biome known as the lungs of the planet, Earth.

(ii) The biodiversity region of India that has the maximum number of amphibians.




Q 28. Represent schematically the steps in prokaryotic transcription?


(i) Describe the complexities that occur in the eukaryotic transcription?

(ii) Where are UTRs located? What is their significance?

Q 29. (i) Show schematically the process of spermatogenesis, that occurs in a human male?

(ii) Why is a date palm plant considered dioecious?


(i) Show only diagrammatically the development of a Zygote of a dicot plant into an embryo?

(ii) Why does the Zygote of an angiosperm develop only after a certain amount of endosperm is developed?

Q 30.  (a) What is MALT?

(b) (i) Write the scientific name of the causative organism of AIDS.

(ii) How does it spread.

(iii) Mention any three characteristic symptoms of the disease.


(a)          Mention any four methods of detecting cancer?

(b)         Show using arrows the part of the life cycle of Plasmodium that occurs in human body?