SET - 2

Roll No. Candidates must write the Set No on

the title page of the answer book.

SAHODAYA PRE BOARD EXAMINATION – 2024-25

 Please check that this question paper contains 10 printed pages.
 Set number given on the right-hand side of the question paper should be written on
the title page of the answer book by the candidate.
 Check that this question paper contains 33 questions.
 Write down the Serial Number of the question in the left side of the margin before
attempting it.
 15 minutes time has been allotted to read this question paper. The question paper will
be distributed 15 minutes prior to the commencement of the examination. The
students will read the question paper only and will not write any answer on the
answer script during the period. Students should not write anything in the question
paper.

CLASS – XII
Sub.: BIOLOGY (044)
Time Allowed : 3 hours Maximum Marks: 70
General Instructions:
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions.
(iii) Section – A has 16 questions of 1 mark each; Section – B has 5 questions of 2 marks
each; Section – C has 7 questions of 3 marks each; Section – D has 2 case-based
questions of 4 marks each; and Section – E has 3 questions of 5 marks each.
(iv) There is no overall choice. However, internal choices have been provided in some
questions. A student has to attempt only one of the alternatives in such questions.
(v) Wherever necessary, neat and properly labeled diagrams should be drawn.
SECTION – A
01. The Earth Summit held in Rio de Janeiro in 1992 was called
(a) for immediate steps to discontinue use of CFCs that were damaging the ozone
layer
(b) to reduce CO2 emissions and global warming

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 (c) for conservation of biodiversity and sustainable utilization of its benefits
(d) to assess threat posed to native species by invasive weed species.
02. Which of the following statements about productivity is true?
(a) Primary productivity of all ecosystems is constant.
(b) Primary productivity depends on the plant species inhabiting a particular area.
(c) Net primary productivity is the amount of biomass available for consumption
by carnivores.
(d) Secondary productivity is defined as the rate of formation of new organic
matter by decomposers.
03. Which of the following would be true of a species with an opportunistic life history?
(a) Members of the species take a relatively long time to reach reproductive age.
(b) They are regulated mostly by density-dependent factors.
(c) They produce large numbers of offspring.
(d) The population usually stabilizes near carrying capacity.
04. Which of the following statements is incorrect regarding RNA interference?
(a) It is a method of cellular defense
(b) The introduction of DNA into the host cell produces both sense and anti-sense
RNA.
(c) It involves silencing of a specific mRNA
(d) Using a retroviral vector nematode specific was introduced into gene the host
plant.
05. I. ..A... is the ability of a cell to take up foreign DNA
II. The cell is treated with specific concentration of a divalent cation such as ...B.
to Increase pore size in cell wall
III. In ….C... method recombinant DNA is directly injected into the nucleus of an
animal cell, the most appropriate option regarding A. B and C is
(a) A-Competency, B- Calcium, C-gene gun method
(b) A-Transformation, B-Sodium, C-microinjection method
(c) A-Competency, B-Calcium, C-microinjection method
(d) A-Transformation, B- Sodium, C-gene gun method
06. Match the following columns and select the correct option :
I II
(A) Dragonflies (i) Biocontrol agent of several plant
Pathogens
(B) Bacillus (ii) Get rid of mosquitoes
thuringiensis
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 (C) Glomus (iii) Narrow spectrum
insecticidal applications
(D) Baculoviruses (iv) Biocontrol agents of lepidoteran
plant pests
(v) Absorb phosphorus from soil
(a) A-ii, B-iv, C-v, D-iii (b) A-iii, B-v, C-iv, D-i
(c) A-ii, B-i, C-iii, D-iv (d) A-ii, B-iii, C-iv, D-v
07. Foetus receives some antibodies from the mother through placenta during pregnancy.
This is an example of
(a) Naturally acquired active immunity
(b) Artificially acquired passive immunity
(c) Naturally acquired passive immunity
(d) Artificially acquired active immunity
08. In a population of 1000 individuals, 360 belong to genotype AA, 480 to Aa and
remaining 160 to aa. Based in this date the frequency of allele A in the population is
(a) 0.5 (b) 0.6
(c) 0.7 (d) 0.4
09. Proteinaceous factors are required to initiate translation. The correct consequences for
translation with the mRNA in an eukaryote are
(a) Ribosome binds to UTR → cognate tRNA binds to codon.
(b) Smaller sub unit binds at codon AUG → cognate tRNA binds to codon →
larger sub unit binds to smaller sub unit.
(c) Larger sub unit binds to smaller sub unit → cognate tRNA binds to codon →
peptide bond formation.
(d) Charged tRNA binds to AUG → smaller sub unit binds to mRNA→ larger sub
unit binds to smaller sub unit.
10. Identify the genotype and find out what proportion of the offsprings from cross
AABBCC  AaBbCc will be completely heterozygous for all genes segregated
independently.
(a) 1/8 AaBbCc (b) 1/8 AaBbCc
(c) 1/16 AaBbCc (d) 1/16 AaBbCC
11. Identify the correct statement on inhibin.
(a) Is produced by nurse cells in testis and inhibits the secretion of LH
(b) Inhibits the secretion of LH, FSH and prolactin
(c) Is produced by granulosa cells in ovary and inhibits the secretion of FSH
(d) Is produced by granulosa cells in ovary and inhibits the secretion of LH.

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12. The figure given below shows megasporogenesis and development of typical female
gametophyte in angiosperms. In which of the following options all divisions (D1 to
D5) and structure (S) are correctly identified?

D1 D2 D3 D4 D5 S
(a) Meiosis I Meiosis II Mitosis Mitosis Mitosis Microgametophyte
(b) Meiosis I Meiosis II Mitosis Mitosis Mitosis Embryo
(c) Meiosis I Meiosis II Mitosis Mitosis Mitosis Embryo sac
(d) Mitosis Meiosis Mitosis Mitosis Mitosis Embryo sac
In the following questions a statement of assertion followed by a statement of reason is
given. Choose the correct answer out of the following choices.
(a) Both Assertion and Reason are true and Reason is the correct
explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is not the correct
explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.
13. Assertion: In National parks, cultivation of land and grazing is not permitted.
Reason : National park is meant for protection of both flora and fauna.
14. Assertion : Detritivores and decomposers have no place in ecological pyramid.
Reason : Detritivores and decomposers do not play any vital role in the ecosystem.
15. Assertion : A temperature control system is an important requirement for bioreactor.
Reason : Every microorganism or enzyme is functional only at an optimum
temperature conditions.
16. Assertion : Primary transcripts in eukaryotes are nonfunctional.
Reason : Methyl guanosine triphosphate is attached to 5'-end of mRNA.
SECTION – B
17. ATTEMPT EITHER OPTION A OR B.
A.
"In a food-chain, a trophic level represents a functional level, not a species." Explain.
Or

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 B.
'The Evil Quartet' describes the rates of species extinction due to human activities.
Explain how the population of organisms is affected by fragmentation the habitats.
18. Identify the labelled items B, C, D & E in the flow chart given below.

19. (a) In a case of polyembryony if an embryo develop from the synergid and
another from the nucellus, which one would be haploid & which one would be
diploid?
(b) Mention the factors that are crucial for storage of mature seeds.
20. Fill in the blank (i), (ii), (iii), (iv) with name of the mammals of Australia.
Marsupial Mammal Placental Mammal
Marsupial mole (i)
Spotted cuscus (ii)
(iii) Flying phalanger
(iv) Bob cot
21. Give the binomials of two types of yeast and the commercial bioactive products they
help to produce.
SECTION – C
22. The above picture shows development of different stages of male gametophyte.

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 (a) The chemical composition of labeled part ‘b’ in the given figure plays a very
important role in its survival for a long period of time. How is it possible?
(b) The fate of labeled part ‘f’ varies in certain percentage of flowering plants
prior to dehiscence & post dehiscence. Justify the statement
(c) What will happen it labeled part ‘C’ is absent in the structure of male
gametophyte?
23. ATTEMPT EITHER OPTION A OR B.
A.
(i) Write the importance of measuring the size of a population in a habitat or an
ecosystem.
(ii) Explain with the help of an example how the percentage cover is a more
meaningful measure of population size than mere numbers.
OR
B.
(i) Predation is usually referred to as a detrimental association. State any three
positive roles that a predator plays in an ecosystem.
(ii) What is pseudocopulation. How it is exhibited explain with an example.
24. A cross is made between different homozygous pea plants for contrasting flower
positions.
(a) Find out the position of flowers in F1 generation on the basis of genotypes.
(b) Work out the cross upto F2 generation.
(c) Compute the relative fraction of various genotypes in the F2 generation?
25. (a) While doing a PCR, 'denaturation' step is missed. What will be its effect on
the process?
(b) For selection of recombinants, insertional inactivation of antibiotic marker has
been superceded by insertional inactivation of a marker gene coding for a
chromogenic substrate. Give reasons.
26. (a) Name any two autotrophic microbes and state how they serve as biofertilizers.
(b) Water samples were collected at points A, B and C in a segment of a river
near a sugar factory and tested for BOD level. The BOD levels of samples A,
B and C were 400 mg/L, 480 mg/L and 8 mg/L respectively. What is this
indicative of? Explain why the BOD level gets reduced considerably at the
collection point C?

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27. How quantitative inheritance different from qualitative inheritance. Explain with
example based on synthesis of globin chain molecule in blood.
28. (a) According to Darwinian theory of natural selection the rate of appearance of
new forms is linked to the life-cycle or the life-span of an organism. Explain
with the help of an example.
(b) State a reason for the increased population of dark coloured moths with the
loss of lichens (on tree barks) during industrialization period in England.
SECTION – D
29. Infertility could be explained as a problem in conceiving a baby by a couple, majorly
caused by a medical issue faced by a person or both in the couple. A recent report
published by the Indian Society of Assisted Reproduction (ISAR) has suggested that
approximately 10-14% of Indian couples face this issue.
Infertility is a medical condition in which a couple faces issues conceiving a baby.
Some recent research has also said that it is a lifestyle growing day by day. Various
medical technologies have come now to cope with these conditions, which could help
to diagnose and correct treatment of some of these disorders and enable couples to
have children.

(A) (B)

(C) (D)

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 (a) Identify the given methods / ART in the figure A, B, C, D.
Attempt either option subpart b or c.
(b) Suggest and explain the assisted reproductive technique which will help a
couple to have children where the female had a blockage in the fallopian tube
and the male partner had a low sperm count.
OR
(c) Name & describe the technique that can help a healthy married woman who is
unable to produce viable ova, but wants to bear a child.
(d) Give the major causes of infertility in couples.
30. The image below describes the molecular diagnostic procedures.

(a) Write any two biochemical molecular diagnostic procedure for early detection
of viral infection.
Attempt either option subpart b or c.
(b) Which technique is used to detect gene mutation in case of suspected cancer
patient & how this technique is used.
OR
(c) Name and explain the technique that is based on the principles of antigen and
antibody interaction. Can this technique be used in the molecular diagnosis of
a genetic disorder, such as phenylketonuria?
(d) Name two human disease that is being studied by transgenic model.
SECTION – E
31. (a) The image below represents the replication of a retrovirus.
In the image, steps 1- 5 depict different stages in the invasion of the retrovirus
into the host cell and steps 6-9 show the invasion of the host DNA and the
processes resulting out of it.
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 (i) Why does the retrovirus need to use reverse transcriptase to infect the
host genome?
(ii) What is the significance of step 7 and 8 (after the viral genome enters
the host nucleus) as shown in the diagram?
(b) All human beings have cellular oncogenes but only a few suffer from cancer
disease. Give reasons.
(c) A person shows strong unusual hypersensitive reactions when exposed to
certain substances present in the air, identify the condition. Name the cells
responsible for such reactions. What precaution should be taken to avoid such
reactions?
Or
(a) Why is tobacco smoking associated with rise in blood pressure and
emphysema (oxygen deficiency in the body)? Explain.
(b) Name the plant source of the drug popularly called "smack'. How does it
affect the body of the abuser?
(c) Why docs a doctor administer tetanus antitoxin and not a tetanus vaccine to a
child injured in a roadside accident with a bleeding wound? Explain.
32. Attempt A or B
A. Maya has been trying to conceive for a few months. She started charting her
basal body temperature and decided to undergo hormonal testing over the
course of her menstrual cycle. The provided graph shows the hormonal
changes and the basal body temperature during her menstrual period.

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 (i) How could a consistent high level of hormone A and low level of
hormone D impact the menstrual cycle?
(ii) Observing the peak of hormone C after 14th day of menstruation cycle
on Maya’s graph, discuss the implications of sustained high levels of
hormone C during early pregnancy stages. After reviewing Maya’s
graph, comment on the chances of her potential pregnancy.
B. (i) Does self incompatibility impose any restrictions autogamy? Give
reasons and suggest the method of pollination in such plants.
(ii) In which plant groups is hydrophilic pollination commonly found, and
how do the pollen grains of hydrophilic flowers protect themselves
from water?
(iii) A guava has 200 viable seeds. How many total gametes are required to
produce the above mentioned seeds?
33. (a) If the genetic code consisted of four bases per codon instead of 3 bases pair
codon, then what will be the possible number of codon that code for 20 types
of amino acids? (Given the stops codon are same).
(b) Given below is a stretch of DNA showing the coding strand of a structural
gene of a transcription unit?
5 -ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TAA—
3'
Write the corresponding template strand and the mRNA strand that will be
transcribed, along with its polarity.
(c) Mention the role of ribosomes in peptide bond formation. How does ATP
facilitate it?
(d) Diagrammatically represent mRNA having sequence coding for tyrosine &
the anticodon of t-RNA for the same amino acid.
OR
(a) Gene encoding RNA polymerase I and III have been affected by mutation in a
cell. Explain its impact on the synthesis of polypeptide, stating reasons.
32 35
(b) Hershey & Chase selected P and S for their experiment. What was the
reason of selection of only these 2 elements to prove that DNA is the genetic
bacterial?
(c) A single base mutation in a gene may not ‘always’ result in loss or gain of
functions. Do you think the statement is correct defend your answer.
(d) Explain the significance of satellite DNA in DNA fingerprinting technique.
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