CBSE Class 12 Board Exam Biology 2014

1. Algae and fungi usually shift to sexual mode of reproduction during unfavourable conditions. Why?
2. Define pseudocarp and give examples.
3. Identify ‘x’ and ‘y’ in the following diagram.

4. What do you understand by ‘contact inhibition’?
5. What are ‘molecular scissors’? Why are they called so?
6. Agrobacterium tumefaciens is known as a natural genetic engineer. Give reason to support the statement.
7. What type of biodiversity is represented by the following?
(i) 50,000 different strains of rice in India.
(ii) Estuaries and alpine meadows in India.
8. An NGO working for environment found enormous algae population flourishing in a lake, which is detrimental to fish and other aquatic animals. What can be the reason?
9. Seeded fruits have several advantages over the seedless fruits. Explain.
10. Study the pedigree chart given below and answer the questions that follow.

(i) Give the genotype of the parents in generation I.
(ii) Is the trait autosomal or X-linked? Name one disease in which such trait is involved.
11. How do contraceptives like (i) lUDs and (ii) Saheli, help to prevent unwanted pregnancies?
12. Differentiate between dominance and epistasis.
OR
Both strands of DNA do not get copied during transcription. Why?
13. Enlist the advantages of artificial insemination over natural breeding method.
14. Plant tendrils are derived from stem in Passiflora and from leaves in Pisum sativum.
(i) Are these structures homologous or analogous? Explain.
(ii) What kind of evolution results in formation of such structures?
15. What novel strategy is adopted to prevent Meloidogyne incognitia from infecting the roots of tobacco plant?
16. Ecological pyramids show feeding relationship and flow of energy or biomass through different trophic levels. What can be the limitations of such pyramids?
17. The government has taken many initiatives to reduce vehicular air pollution in Delhi. What are these initiatives?
18. Many parasites survive and thrive in their hosts. What adaptations help them to sustain?

19. (i) Draw a neat and labelled diagram of a fertilized embryo sac.
(ii) Describe briefly the type of fertilization found only in angiosperms.
20. (i) State Hardy Weinberg’s principle.
(ii) According to HW principle, what conditions are absolutely necessary to maintain the genetic equilibrium?
21. (i) Draw a labelled diagram of charged fRNA showing methionine attached, codon and anticodon.
(ii) Describe the process involved in amino acid attachment.
22. (i) Name the parasite that causes malignant malaria in humans.
(ii) Trace the stages in its life cycle with the help of a flowchart.
23. (i) What do you understand by IPM?
(ii) How are baculoviruses beneficial in IPM programme?
OR
(i) Explain bio-fortification with example. What are its objectives?
(ii) Write few advantages of single cell protein.
24. Discuss the role of gene therapy in curing SCID. Can we consider it as a permanent cure?
25. (i) What are antibiotics? List few characteristics of a good antibiotic.
(ii) Newer antibiotics are required to combat the same pathogens. Why?
26. What is so special about tropics that they might account for their great biological diversity?
27. (i) A rise in atmospheric temperature has been observed since last three decades. What is the cause of such change?
(ii) Explain few effects of warming of earth.

28. (i) Draw a labelled diagram of the T.S. of anther of angiosperms.
(ii) Explain the functions of different wall layers of anther.
OR
(i) The growth, maintenance and functions of the male reproductive organs are under the hormonal control. Explain.
(ii) Give a schematic representation of gametogenesis in human females.
29. (i) The length of a double helical DNA in a human cell is far greater than the dimensions of a typical nucleus. How does such long polynucleotide get packed?
(ii) What is the principle of DNA fingerprinting technique?
OR
(i) How did Griffith prove the DNA transformation principle? Describe the experiments he performed.
(ii) RNA is not considered a suitable genetic material. Why?
30. Riya is a young activist who protests against the research and development of genetically modified crops. According to her, GM crops will create severe health and environmental issues and hence they should not be encouraged.
Do you support her protest against GM crops? Explain your view.

 

 

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