MODEL QUESTION PAPER 2024-25

CLASS XII
BIOLOGY(044)
MaximumMarks:70 Time:3hours
GeneralInstructions:
(i) Allquestionsarecompulsory.
(ii) Thequestionpaperhasfivesectionsand33questions. Allquestionsare compulsory.
(iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each;
Section–Chas7questionsof3markseach;Section–Dhas2case-basedquestionsof4 marks
each; and Section–E has 3 questions of 5 marks each.
(iv) Thereisnooverallchoice.However,internalchoiceshavebeenprovidedinsome
questions.Astudenthastoattempt onlyoneofthealternativesinsuchquestions.
(v) Wherevernecessary,neatandproperlylabeleddiagramsshouldbedrawn.

SECTION-A
Q.N
Question Marks
o.
The technique called Gamete Intra Fallopian Transfer (GIFT) is recommended for those 1
1.
females
(a) who cannot produce an ovum
(b) who cannot retain the foetus inside uterus
(c) who cannot provide suitable environment for fertilization
(d) all of these

1
2. Given below are four contraceptive methods and their modes of action. Select the
correct match:

S.No. Method S.No Mode of action

a) Condom (i) Ovum not able to reach Fallopian
tube
b) Vasectomy (ii) Prevents ovulation
c) Pill (iii) Prevents sperm reaching the cervix
d) Tubectomy (iv) Semen contains no sperms

(a) a)–(i) b)–(ii) c)–(iii) d)–(iv)

(b) a)–(ii) b)–(iii) c)–(iii) d)–(i)
(c) a)–(iii) b)–(iv) c)–(ii) d)–(i)
(d) a)–(iv) b)–(i) c)–(iii) d)–(ii)

1
 In oocyte secondary maturation occurs in 1
3
(a) ovary
(b) abdominal cavity
(c) Fallopian tube
(d) uterus.

1
4 Evolutionary convergence is development of a
(a) Common set of functions in groups of different ancestry.
(b) Dissimilar set of functions in closely related groups.
(c) Common set of structures in closely related groups.
(d) Dissimilar set of functions in unrelated groups.

5. Apis mellifera are killer bees possessing toxic bee venom. Identify the treatment and 1
the type of immunity developed from the given table to treat a person against the
venom of this bee.

Remedy Immunity
(a) Inactivated proteins Active
(b) Proteins of the venom Passive
(c) Preformed antibodies Passive
(d) Dead micro-organisms Active

6. Interferons are most effective in making non-infected cells resistant against the 1
spread of which of the following diseases in humans?
(a) ascariasis
(b) ringworm
(c) amoebiasis
(d) AIDS

7. Which of the following statements best describes the process of double fertilization in 1
flowering plants?
A. Double fertilization involves the fusion of one sperm cell with two egg cells.
B. Double fertilization is the process where two sperm cells each fertilize a different
ovule.
C. Double fertilization involves one sperm cell fertilizing the egg cell, while another
sperm cell fuses with two polar nuclei to form the triploid endosperm.
D. Double fertilization is the fusion of two egg cells with one sperm cell to produce a
zygote.

2
8. The figure below shows the structure of a plasmid. 1

A foreign DNA was ligated at BamH1.Thetransformants were then grown in a medium

containing antibiotics tetracycline and ampicillin.
Choose the correct observation for the growth of bacterial colonies from the given
table

Medium with Tetracycline Medium with Ampicillin

(a) Growth No growth
(b) No growth Growth
(c) No growth No Growth
(d) Growth Growth

9. A national level approach to build up a reproductively healthy society was taken up in 1

our country in
(a) 1950s
(b) 1960s
(c) 1980s
(d) 1990s

10. Sea Anemone gets attached to the surface of the hermit crab. The kind of population 1
interaction exhibited in this case is
(a) amensalism.
(b) commensalism.
(c) mutualism.
(d) parasitism.

3
11. Which of the following food chains is the major conduit for energy flow in terrestrial 1
and aquatic ecosystems respectively?

TerrestrialEcosystem Aquatic Ecosystem

(a) Grazing Grazing
(b) Detritus Detritus
(c) Detritus Grazing
(d) Grazing Detritus

12 In flowering plants, the formation of the endosperm involves a unique type of 1

fertilization. Which of the following statements accurately describes this process?

a) The endosperm is formed by the fusion of a sperm cell with the egg cell, and it is
triploid.

b) The endosperm is formed by the fusion of two sperm cells with two egg cells, and it
is tetraploid.

c) The endosperm is formed by the fusion of one sperm cell with two polar nuclei, and
it is triploid.

d) The endosperm is formed by the fusion of one sperm cell with the egg cell and a
second sperm cell with another egg cell, and it is diploid.

QuestionNo.13to16consistoftwostatements–Assertion(A)andReason(R).Answerthese
questions selecting the appropriate option given below:
A. Both AandRaretrue andRisthecorrectexplanationofA.
B. Both AandRaretrueandRisnotthecorrectexplanationofA.
C. Aistruebut R is false.
D. Ais FalsebutR is true.

13. Assertion : Sickle-cell anaemia is an autosome-linked recessive disorder that can be 1

transmitted if both parents are heterozygous for the gene
Reason : In sickle-cell anaemia, haemoglobin molecule undergoes polymerisation
under low oxygen tension causing the change in shape in RBC

14. Assertion: When white eyed, yellow bodied Drosophila females were hybridized with 1
red eyed, brown-bodied males; and F1 progeny was intercrossed, F2 ratio deviated
from 9 : 3 : 3 : 1.

Reason: When two genes in a dihybrid are on the same chromosome, the
proportion of parental gene combinations is much higher than the non-parental type.

4
15. 1
Assertion : 'Cry' proteins are named so because they are crystal proteins
Reason : 'Cry' proteins are solubilised is acidic environment of insect midgut and
then release toxic core fragments after proteolytic action.

. 1
16.
Assertion: For human populations the age pyramids generally show age distribution
of males and females in a combined diagram
Reason: The shape of age pyramid reflects the growth status of the populations,
whether it is growing, stable or declining

SECTION-B
Identify the areas labelled i, ii, iii and iv in the pie chart given below representing the
17.
biodiversity of plants showing their proportionate number of species of major taxa. 2

A true breeding pea plant, homozygous dominant for inflated green pods is crossed
18. 2
with another pea plant with constricted yellow pods (ffgg).With the help of punnett
square show the above cross and mention the results obtained phenotypically and
genotypicallyinF1generation?
19 Answer the questions based on the dinucleotide shown below. 2
(i) Name the type of sugar guanine base is attached to.
(ii) Identify the 3′ end of the dinucleotide. Give a reason for your answer.

5
20 CTTAAG 2
GAATTC

(a) What are such sequences called ? Name the enzyme used that
recognizes such nucleotide sequences.
(b) What is their significance in biotechnology?
21 (a) Given below is a pyramid of biomass in an ecosystem where each bar 2
representsthestanding crop availablein thetrophic level.Withthe helpofan
example explain the conditions where this kind of pyramid is possible in
nature?

(b) Will the pyramid of energy be also of the same shape in this situation? Give
reason for your response.

OR

(a) Draw a pyramid of numbers where a large number of insects are feeding on
the leaves of a tree. What is the shape of this pyramid?
(b) Will the pyramid of energy be also of the same shape in this situation? Give
reason for your response.
SECTION-C
(a) Mention a product of human welfare obtained with the help of each one of the
22 3
following microbes.
(i) LAB

(ii) Saccharomyces cerevisiae

(iii) Propionibacterium shermanii

(a)State the functions of the following in a prokaryote:

23 3
(i) tRNA

(ii) rRNA

(b) Differentiate between a cistron and an exon.

24 3
(a)Identify the polarity of x to x’ in the diagram below and mention how many more
amino acids are expected to be added to this polypeptide chain.

6
 (b) Mention the codon and anticodon for alanine.
(c) Why are some untranslated sequences of bases seen in mRNA coding for a
polypeptide? Where exactly are they present on mRNA?

25 (a) How is Hardy-Weinberg's expression“(p2+2pq+q2)=1”derived? 3

(b) List any two factors that can disturb the genetic equilibrium.
3
26 Highlight the structural importance of an antibody molecule with a diagram. Name
the four types of antibodies found to give a humoral immune response ,mentioning
the functions of two of them you have studied.
OR
(a) Explain the Life cycle of Plasmodium starting from its entry in the body of female
Anopheles till the completion of its life cycle in humans.
(b) Explain the cause of periodic recurrence of chill and high fever during malarial
attack in humans.

27 Carefully observe the given picture. A mixture of DNA with fragments ranging from 3
200 base pairs to 2500 base pairs was electrophoresed on agarose gel with the
following arrangement.

(a) What result will be obtained on staining with ethidium bromide? Explain with
reason.
(b) The above set-up was modified and a band with250 base pairs was obtained at
X.

7
 What change(s) were made to the previous design to obtain a band at X? Why did
the band appear at the position X?
28 3
(a) Name the two intermediate hosts on which the human liver fluke depends to
complete its life cycle, so as to facilitate parasitisation of its primary host.
State Gause’s competitive exclusion principle.

SECTION-D
Q.no29and30arecasebasedquestions.Eachquestionhassubpartswithinternalchoiceinone
subpart.
29 Study the Pedigree chart given below and answer the questions that follow: 4

(a) Onthebasisoftheinheritancepatternexhibitedinthispedigreechart,what conclusion

can you draw about the pattern of inheritance?
(b) Ifthefemaleishomozygousfortheaffectedtraitinthispedigreechart,then what
percentage of her sons will be affected ?

8
 (c)Give the genotype of offsprings1,2,3and4inIIIgeneration.
OR
(c)In this type of inheritance pattern, out of male and female children which one has
less probability of receiving the trait from the parents. Give a reason.
30. The data below shows the concentration of nicotine smoked by a smoker taking 10 4
puffs/ minute.

(a) With reference to the above graph explain the concentration of nicotine in blood
at 10 minutes.
(b) How will this affect the concentration of carbon monoxide and haem
bound oxygen at 10 minutes?
(c) How does cigarette smoking resulting in high blood pressure and increase in
heart rate?
OR
(c)How does cigarette smoking result in lung cancer and emphysema?

SECTION-E

31 5
Trace the development of megaspore mother cell to the formation of mature embryo
sac in a flowering plant.
OR
Identify and label the parts in the given anatropous ovule.

(i) Name the organic material exine of the pollen grain is made up of. How is this

9
 material advantageous to pollen grain?
(ii) Still it is observed that it does not form a continuous layer around the pollen grain.
Give reason.

32. Explain the role of biotechnology in environmental conservation. In your answer, 5

cover the following points:
1. One biotechnological method used to clean up environmental pollutants.
2. An example of a genetically modified organism (GMO) used in
environmental management.
3. The potential benefits and limitations of using biotechnology for
environmental conservation.
OR
Describe the use of biotechnology in the field of medicine. In your answer,
include:
1. A specific example of a biotechnological product used in medical
treatments.
2. How biotechnology has improved the production of this product.
3. One major challenge associated with the use of biotechnology in medicine.

Explain the hormonal regulation of the menstrual cycle in human females. In your
33. 5
answer, include:
1. The roles of the key hormones involved.
2. The phases of the menstrual cycle and their hormonal regulation.
3. The physiological changes that occur during each phase.
OR
Describe the process of spermatogenesis in human males. In your answer, include:
1. The location where spermatogenesis occurs.
2. The key stages of spermatogenesis and their significance.
3. The role of hormones in regulating spermatogenesis.

10