The CBSE Class 12 Board exams commenced from February and the Biology exam is scheduled for March 14, 2020. Biology is a fairly practical subject with important and technical theory in most of the chapters. Since there are a lot of terms and processes to learn, regular revision is required. To prepare well for your Biology board exam, you should solve ample numbers of sample papers.
Biology sample paper:
Section A (1*5=5)
1. If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is:
a) Autosomal dominant
b) Autosomal recessive
c) Sex-linked dominant
d) Sex-linked recessive
Two genes ‘A’ and ‘B’ are linked. In a dihybrid cross involving these two genes, the F1 heterozygote is crossed with homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation?
a) 1 : 1 : 1: 1
b) 9 : 3 : 3 : 1
c) 3 : 1
d) 1 : 1
2. The role of DNA ligase in the construction of a recombinant DNA molecule is:
a) Formation of hydrogen bonds between sticky ends of DNA fragments
b) Formation of phosphodiester bond between two DNA fragments
c) Ligation of all purine and pyrimidine bases
d) None of the above
3. Acrosomal reaction of the sperm occurs due to:
a) Reactions within the epididymal environment of the male
b) Reactions within the uterine environment of the female
c) Its contact with zona pellucida of the ova
d) Androgens produced in the uterus
4. Tobacco consumption is known to stimulate secretion of adrenaline and nor-adrenaline. The component causing this could be:
b) Tannin Acid
5. Ecotone is:
a) A polluted area
b) The bottom of a lake
c) A zone of transition between two communities
d) A zone of developing commuities
According to Allen’s Rule, the mammals from colder climates have:
a) shorter ears and longer limbs
b) longer ears and shorter limbs\
c) longer ears and longer limbs
d) shorter ears and shorter limbs
Section B (2*7=14)
6. a) Each and every coitus does not result in fertilization and pregnancy. Justify the statement.
b) Mention the name and role of hormones which are involved in regulation of gamete formation in human male.
7. What is biochemical oxygen demand (BOD) test? At what stage of Sewage treatment this test is performed? BOD level of three samples of water labelled as A, B and C are 30 mg/L, 10mg/L and 500 mg/L respectively. Which sample of water is most polluted?
a) Lactic Acid Bacteria (LAB) is commonly used in the conversion of milk into curd. Mention any two other functions of LAB that are useful to humans.
b) Name one alcoholic drinks produced in each of the following ways.
(i) by distillation and (ii) without distillation
8. Describe at least two approaches each for ex-situ conservation and in situ conservation as a strategy for biodiversity conservation.
9. Identify the sex of organism as male or female in which the sex chromosome are found as (i) ZW in bird (ii) XY in Drosophila (iii) ZZ in birds. (iv) XO in grasshopper.
10. T.S. of mammalian testis revealing seminiferous tubules show different types of cell.
(i) Name the two types of cells of germinal epithelium.
(ii) Name of cells scattered in connective tissue and lying between seminiferous tubules. Differentiate between them on the basis of their functions.
‘A fertilized egg is the blue print of future development’. Explain.
11. In Mendel’s breeding experiment on garden pea, the offspring of F2 generation are obtained in the ratio of 25% pure yellow pod, 50% hybrid green pods and 25% green pods State
(i) Which pod colour is dominant
(ii) The Phenotypes of the individuals of F1 generation.
(iii) Workout the cross.
12. (i) State the Hardy- Wienberg principle
(ii) According to this principle, what is the sum total of all allelic frequencies?
(iii) When there is a disturbance in the Hardy-Weinberg equilibrium, what would it result in?
Section C (3*12=36)
13. A person shows unwelcome immunogenic reactions while exposed to certain substances.
a) Name this condition.
b) What common term is given to the substances responsible for this condition?
c) Name the cells and the chemical substances released which cause such reactions
14. In the given figure, one cycle of polymerase chain reaction (PCR) is shown:
a) Name the steps A, B and C.
b) Give the purpose of each of these steps.
c) State the contribution of bacterium Thermus aquaticus in this process.
The development of bioreactors is required to produce large quantities of
a) Give optimum growth conditions used in bioreactors.
b) Draw a well labelled diagram of simple stirred. tank bioreactor.
c) How does a simple stirred. tank. bioreactor differ from sparged stirred tank bioreactor?
15. a) Represent diagrammatically the E. coli. Cloning vector b PBR 322.
b) What is “Insertional Inactivation”?
16. a) Darwin showed that even a slow growing animal like elephant could reach enormous number in absence of checks. With the help of your understanding of growth models, explain when is this possible? Why is this notion unrealistic?
b) How does the shape of age pyramid reflect the growth status of a population?
Compare the two ecological pyramids of biomass given below and explain the situations in which this is possible. Also construct an ideal pyramid of energy if 200,000 joules of sunlight is available.
17. Pollutant released due to human activities (like effluents from industries and homes) can radically accelerate the ageing process of the water body.
a) Explain how does this process occurs during natural ageing of lake.
b) Give the term used for accelerated ageing of water bodies. Also give the term used for the natural ageing of lake.
18. Industrial Melanism. in peppered moth is an excellent example of Natural selection. Justify the statement.
19. What is meant by semi conservative replication? How did Meselson and Stahl prove it experimentally?
20. a) What is somatic hybridisation?
b) Describe the various steps in producing somatic hybrids from protoplasts.
c) Mention any two uses of somatic hybridization.
21. a) Name the parts .X. and .Y. of the transcription unit given below:
b) Write the segment of RNA transcribed from the given DNA
3´ – A T G C A G T A C G T C G T A – 5´ – Template Strand
5´ – T A C G T C A T G C A G C A T – 3´ – Coding Strand.
c) The process of termination during transcription in a prokaryotic cell is being
represented here. Name the label a, b, c and d.
22. a) Mention the main difference between the offspring produced by asexual reproduction and progeny produced by sexual reproduction.
b) Higher organism have resorted to sexual reproduction inspite of its complexity. Why?
c) Offspring produced by asexual reproduction are referred to as clones. Why?
b) How does primary sludge differ from activated sludge?
c) What type of changes in the sludge are carried out in anaerobic sludge digester? Give the composition of biogas produced in the sewage treatment plant.
24. a) The map distance in certain organism between genes A & B is 4 units between B & C is units, & between C & D is 8 units which one of these gene paves will show more recombination frequency? Give reason.
b) Name the phenomena that occur when homologous chromosomes do not separate during meiosis.
c) What is pedigree Analysis? How is it useful?
Section E (5*3=15)
25. a) What is meant by ecological succession?
b) Describe the different stages in which succession occurs?
c) Why is secondary succession faster than primary succession?
a) What is meant by ecological pyramid? Distinguish between upright & inverted pyramids?
b) With the help of one example each, show that pyramid of number can be both upright as well as inverted.
c) Name the ecological pyramid that is always upright?
26. a) Give reason for the following:
(i) The first half of the menstrual cycle is called follicular phase as well as proliferative phase.
(ii) The second half of the menstrual cycle is called luteal phase as well as secretory phase.
b) Explain the development of human embryo with diagrams.
a) Differentiate between chasmogamous and cleistogamous flowers
b) Enlist the advantages offered by seeds to angiosperms.
c) Give any three advantages of sexual incompatibility.
27. Discuss the role of lymphoid organs in the immune response. Explain the different types of lymphoid organs giving two examples of each type in humans.
It was diagnosed by a specialist that the immune System of the body of a patient has been suppressed. Describe the infection & the mechanism of its proliferation in the body.